My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a
small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify.
From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad
thing because it would allow extra tuned circuits to give better image >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a
small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure
(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify.
From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad
thing because it would allow extra tuned circuits to give better image
rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric
noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on
the downlead. If the down-converter is adjacent to the HF receiver,
there will be significant losses at VHF in the downlead, as the aerial
needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >signal could be radiated by the aerial - especially if it happens to lie
at a frequency where the dipole has another resonance or the dipole and >downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial
(the sleeve dipole has a 'cold' bottom end and could be joined directly
onto the converter box). The HT and LT could be supplied either by a >separate multi-core cable or by superimposing 40v A.C. at 50c/s on the
co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an >auto-transformer to give 250v H.T. and the secondary could give 6.3v or
12.6v to run the heaters.
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >Mc/s) and I have thought about making a sleeve dipole for that band. My >VHF receiver is an Eddystone 770R, which covers the band but only in a >small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure >(although Mullard don't quote one in their data sheet). If I >triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify. >From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct >neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad >thing because it would allow extra tuned circuits to give better image >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric
noise still dominates.
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >> >Mc/s) and I have thought about making a sleeve dipole for that band. My >> >VHF receiver is an Eddystone 770R, which covers the band but only in a
small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges >> >of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >> >not necessarily the expensive 'cult' ones which everyone seems to regard >> >as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure
(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify. >> >From the data sheet, with 200v on anode and grid 2 and an anode current >> >of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >> >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as >> >a mixer, I might need one more stage of RF gain to get the signal up to >> >a level where the mixer noise is negligible - but this isn't such a bad >> >thing because it would allow extra tuned circuits to give better image
rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric
noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >the downlead. If the down-converter is adjacent to the HF receiver,
there will be significant losses at VHF in the downlead, as the aerial >needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >signal could be radiated by the aerial - especially if it happens to lie
at a frequency where the dipole has another resonance or the dipole and >downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >(the sleeve dipole has a 'cold' bottom end and could be joined directly >onto the converter box). The HT and LT could be supplied either by a >separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an >auto-transformer to give 250v H.T. and the secondary could give 6.3v or >12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>> >Mc/s) and I have thought about making a sleeve dipole for that band. My >>> >VHF receiver is an Eddystone 770R, which covers the band but only in a
small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges >>> >of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >>> >not necessarily the expensive 'cult' ones which everyone seems to regard >>> >as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure
(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify. >>> >From the data sheet, with 200v on anode and grid 2 and an anode current >>> >of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >>> >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as >>> >a mixer, I might need one more stage of RF gain to get the signal up to >>> >a level where the mixer noise is negligible - but this isn't such a bad >>> >thing because it would allow extra tuned circuits to give better image
rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric
noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>the downlead. If the down-converter is adjacent to the HF receiver,
there will be significant losses at VHF in the downlead, as the aerial >>needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>signal could be radiated by the aerial - especially if it happens to lie
at a frequency where the dipole has another resonance or the dipole and >>downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>(the sleeve dipole has a 'cold' bottom end and could be joined directly >>onto the converter box). The HT and LT could be supplied either by a >>separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an >>auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL >handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>>> >Mc/s) and I have thought about making a sleeve dipole for that band. My >>>> >VHF receiver is an Eddystone 770R, which covers the band but only in a >>>> >small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges >>>> >of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>> >scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >>>> >not necessarily the expensive 'cult' ones which everyone seems to regard >>>> >as having magical powers. The EF91 is plentiful and cheap as New Old >>>> >Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television >>>> >sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>> >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>> >the noise and increase the maximum frequency it could usefully amplify. >>>> >From the data sheet, with 200v on anode and grid 2 and an anode current >>>> >of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>> >Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >>>> >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as >>>> >a mixer, I might need one more stage of RF gain to get the signal up to >>>> >a level where the mixer noise is negligible - but this isn't such a bad >>>> >thing because it would allow extra tuned circuits to give better image >>>> >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>>the downlead. If the down-converter is adjacent to the HF receiver, >>>there will be significant losses at VHF in the downlead, as the aerial >>>needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>signal could be radiated by the aerial - especially if it happens to lie >>>at a frequency where the dipole has another resonance or the dipole and >>>downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>(the sleeve dipole has a 'cold' bottom end and could be joined directly >>>onto the converter box). The HT and LT could be supplied either by a >>>separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>co-ax and feeding it into the 200-220-240v tappings.of a mains >>>transformer primary. The full primary winding would act as an >>>auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL >>handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
There's not a single person on this group
today who can really add any value here.
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com> >>wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>>>> >Mc/s) and I have thought about making a sleeve dipole for that band. My >>>>> >VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>> >small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that >>>>> >would allow me to use an HF communications receiver or the lower ranges >>>>> >of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>> >scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >>>>> >not necessarily the expensive 'cult' ones which everyone seems to regard >>>>> >as having magical powers. The EF91 is plentiful and cheap as New Old >>>>> >Stock, so that seems like a good valve to start playing about with. >>>>> >
The EF91 was used as an RF amplifier in the input stages of television >>>>> >sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>> >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>> >the noise and increase the maximum frequency it could usefully amplify. >>>>> >From the data sheet, with 200v on anode and grid 2 and an anode current >>>>> >of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>> >cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>> >Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >>>>> >cathode mode, but it allows the valve to be triode strapped for low >>>>> >noise without instability problems or the dependence on neutralising >>>>> >that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as >>>>> >a mixer, I might need one more stage of RF gain to get the signal up to >>>>> >a level where the mixer noise is negligible - but this isn't such a bad >>>>> >thing because it would allow extra tuned circuits to give better image >>>>> >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF >>>>receiver is almost certain to suffer from strong HF signals picked up on >>>>the downlead. If the down-converter is adjacent to the HF receiver, >>>>there will be significant losses at VHF in the downlead, as the aerial >>>>needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>signal could be radiated by the aerial - especially if it happens to lie >>>>at a frequency where the dipole has another resonance or the dipole and >>>>downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>(the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>onto the converter box). The HT and LT could be supplied either by a >>>>separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>co-ax and feeding it into the 200-220-240v tappings.of a mains >>>>transformer primary. The full primary winding would act as an >>>>auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour. >>>However, there should be tons of info on this in one of the old ARRL >>>handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group
today who can really add any value here. Ham group, Liz; ham group.
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>>>>> Mc/s) and I have thought about making a sleeve dipole for that band. My >>>>>> VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>> small portion of the whole scale. While I am improvomg the aerial >>>>>> system, I could also make a crystal-controlled down-converter, that >>>>>> would allow me to use an HF communications receiver or the lower ranges >>>>>> of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>> scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >>>>>> not necessarily the expensive 'cult' ones which everyone seems to regard >>>>>> as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>> Stock, so that seems like a good valve to start playing about with. >>>>>>
The EF91 was used as an RF amplifier in the input stages of television >>>>>> sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>> (although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>> the noise and increase the maximum frequency it could usefully amplify. >>>>>> From the data sheet, with 200v on anode and grid 2 and an anode current >>>>>> of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>> cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>> Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >>>>>> cathode mode, but it allows the valve to be triode strapped for low >>>>>> noise without instability problems or the dependence on neutralising >>>>>> that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as >>>>>> a mixer, I might need one more stage of RF gain to get the signal up to >>>>>> a level where the mixer noise is negligible - but this isn't such a bad >>>>>> thing because it would allow extra tuned circuits to give better image >>>>>> rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>>> the downlead. If the down-converter is adjacent to the HF receiver,
there will be significant losses at VHF in the downlead, as the aerial >>>> needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>> signal could be radiated by the aerial - especially if it happens to lie >>>> at a frequency where the dipole has another resonance or the dipole and >>>> downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>> (the sleeve dipole has a 'cold' bottom end and could be joined directly >>>> onto the converter box). The HT and LT could be supplied either by a
separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>> co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>> 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL
handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group
today who can really add any value here. Ham group, Liz; ham group.
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >> >> >Mc/s) and I have thought about making a sleeve dipole for that band. My >> >> >VHF receiver is an Eddystone 770R, which covers the band but only in a >> >> >small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges >> >> >of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >> >> >not necessarily the expensive 'cult' ones which everyone seems to regard >> >> >as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television >> >> >sets working at about 45 Mc/s, so it can't have too bad a noise figure >> >> >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >> >> >the noise and increase the maximum frequency it could usefully amplify. >> >> >From the data sheet, with 200v on anode and grid 2 and an anode current >> >> >of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >> >> >Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >> >> >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as >> >> >a mixer, I might need one more stage of RF gain to get the signal up to >> >> >a level where the mixer noise is negligible - but this isn't such a bad >> >> >thing because it would allow extra tuned circuits to give better image >> >> >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric
noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on
the downlead. If the down-converter is adjacent to the HF receiver,
there will be significant losses at VHF in the downlead, as the aerial
needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator
signal could be radiated by the aerial - especially if it happens to lie
at a frequency where the dipole has another resonance or the dipole and
downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial
(the sleeve dipole has a 'cold' bottom end and could be joined directly
onto the converter box). The HT and LT could be supplied either by a
separate multi-core cable or by superimposing 40v A.C. at 50c/s on the
co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or
12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL
handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I have read most of that sort of literature in the past and still have
copies of most of it but don't remember this particular approach being
used before - that was why I though it might make a good fun project.
There are some grounded-grid circuits but they use triodes intended for
the purpose. There are cascode circuits with double (and sometimes two >single) triodes but, again, the triodes are intended for that purpose.
The idea of using a bog-standard descendent of the ubiquitous EF50 for >frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a >triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the >wideband front end of a noise-measuring set that I designed; it gave
very satisfactory results.
On Sat, 09 Nov 2024 21:03:12 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com> >>>wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid >>>>(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>>>>> >Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>> >small portion of the whole scale. While I am improvomg the aerial >>>>>> >system, I could also make a crystal-controlled down-converter, that >>>>>> >would allow me to use an HF communications receiver or the lower ranges >>>>>> >of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>> >scale length.
It's been a few years since I designed anything with valves, so I >>>>>> >thought I might have a go at making a down-converter using valves - but >>>>>> >not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>> >Stock, so that seems like a good valve to start playing about with. >>>>>> >
The EF91 was used as an RF amplifier in the input stages of television >>>>>> >sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>> >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>> >the noise and increase the maximum frequency it could usefully amplify. >>>>>> >From the data sheet, with 200v on anode and grid 2 and an anode current >>>>>> >of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>> >cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>> >Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low >>>>>> >noise without instability problems or the dependence on neutralising >>>>>> >that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to >>>>>> >a level where the mixer noise is negligible - but this isn't such a bad >>>>>> >thing because it would allow extra tuned circuits to give better image >>>>>> >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF >>>>>receiver is almost certain to suffer from strong HF signals picked up on >>>>>the downlead. If the down-converter is adjacent to the HF receiver, >>>>>there will be significant losses at VHF in the downlead, as the aerial >>>>>needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>>signal could be radiated by the aerial - especially if it happens to lie >>>>>at a frequency where the dipole has another resonance or the dipole and >>>>>downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>>(the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>>onto the converter box). The HT and LT could be supplied either by a >>>>>separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>>co-ax and feeding it into the 200-220-240v tappings.of a mains >>>>>transformer primary. The full primary winding would act as an >>>>>auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>>12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour. >>>>However, there should be tons of info on this in one of the old ARRL >>>>handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group >>today who can really add any value here. Ham group, Liz; ham group.
I know a lot of receiver designers, and the older ones are all Hams.
Joe
On Sat, 09 Nov 2024 16:48:10 -0500, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Sat, 09 Nov 2024 21:03:12 +0000, Cursitor Doom <cd@notformail.com> >>wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com> >>>>wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid >>>>>(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>>> >small portion of the whole scale. While I am improvomg the aerial >>>>>>> >system, I could also make a crystal-controlled down-converter, that >>>>>>> >would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>>> >scale length.
It's been a few years since I designed anything with valves, so I >>>>>>> >thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>>> >Stock, so that seems like a good valve to start playing about with. >>>>>>> >
The EF91 was used as an RF amplifier in the input stages of television >>>>>>> >sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>>> >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>>> >the noise and increase the maximum frequency it could usefully amplify.
From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>>> >cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>>> >Pi tank or by tapping the L or the C of an input tumed circuit. >>>>>>> >
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low >>>>>>> >noise without instability problems or the dependence on neutralising >>>>>>> >that a cascode stage would have (especially the need for correct >>>>>>> >neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad
thing because it would allow extra tuned circuits to give better image >>>>>>> >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >>>>>>>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF >>>>>>receiver is almost certain to suffer from strong HF signals picked up on >>>>>>the downlead. If the down-converter is adjacent to the HF receiver, >>>>>>there will be significant losses at VHF in the downlead, as the aerial >>>>>>needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>>>signal could be radiated by the aerial - especially if it happens to lie >>>>>>at a frequency where the dipole has another resonance or the dipole and >>>>>>downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>>>(the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>>>onto the converter box). The HT and LT could be supplied either by a >>>>>>separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>>>co-ax and feeding it into the 200-220-240v tappings.of a mains >>>>>>transformer primary. The full primary winding would act as an >>>>>>auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>>>12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due >>>>>respect - will be able to assist you very much in this endeavour. >>>>>However, there should be tons of info on this in one of the old ARRL >>>>>handbooks. If you have any from the early 60s lying around it should >>>>>be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and >>>trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people >>>here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group >>>today who can really add any value here. Ham group, Liz; ham group.
I know a lot of receiver designers, and the older ones are all Hams.
Joe
+1
That's where all the expertise is. Esp. with tubes.
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>>>>>> Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>>> small portion of the whole scale. While I am improvomg the aerial >>>>>>> system, I could also make a crystal-controlled down-converter, that >>>>>>> would allow me to use an HF communications receiver or the lower ranges >>>>>>> of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>>> scale length.
It's been a few years since I designed anything with valves, so I >>>>>>> thought I might have a go at making a down-converter using valves - but >>>>>>> not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>>> Stock, so that seems like a good valve to start playing about with. >>>>>>>
The EF91 was used as an RF amplifier in the input stages of television >>>>>>> sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>>> (although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>>> the noise and increase the maximum frequency it could usefully amplify. >>>>>>> From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>>> cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>>> Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low >>>>>>> noise without instability problems or the dependence on neutralising >>>>>>> that a cascode stage would have (especially the need for correct >>>>>>> neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to >>>>>>> a level where the mixer noise is negligible - but this isn't such a bad >>>>>>> thing because it would allow extra tuned circuits to give better image >>>>>>> rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>>>> the downlead. If the down-converter is adjacent to the HF receiver, >>>>> there will be significant losses at VHF in the downlead, as the aerial >>>>> needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>> signal could be radiated by the aerial - especially if it happens to lie >>>>> at a frequency where the dipole has another resonance or the dipole and >>>>> downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>> (the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>> onto the converter box). The HT and LT could be supplied either by a >>>>> separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>> co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>> 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL
handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group
today who can really add any value here. Ham group, Liz; ham group.
2 metres is pretty much DC nowadays anyhow.
HF receivers don’t have to have good noise performance because the atmosphere is so noisy, and AFAICT they usually don’t. Intermod is more of an issue.
The atmosphere is quieter above 100 MHz, though, so you care more about the Rx noise figure.
A mixer front end is going to have a noise figure of 6 dB or so, on account of the conversion loss, and that adds to the NF of the HF back end.
Some gain ahead of the mixer, and some more following the band select
filter should help a lot. Don’t overdo it, of course.
Cheers
Phil Hobbs
My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a
small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
Cursitor Doom <cd@notformail.com> wrote:
[...]
There's not a single person on this group
today who can really add any value here.
You do them a dis-service, there are some people here who can think with
an open mind. Even if the ideas they come up with wouldn't work, trying
to find out or explain why they wouldn't work is a good exercise and may
lead to a better solution than just asking hams what they have done
before.
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres
(144 Mc/s) and I have thought about making a sleeve dipole for that
band. My VHF receiver is an Eddystone 770R, which covers the band
but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled
down-converter, that would allow me to use an HF communications
receiver or the lower ranges of the 770R, so that the band 2 Mc/s
wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves -
but not necessarily the expensive 'cult' ones which everyone seems
to regard as having magical powers. The EF91 is plentiful and
cheap as New Old Stock, so that seems like a good valve to start
playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad
a noise figure (although Mullard don't quote one in their data
sheet). If I triode-strapped it and ran it in grounded grid mode,
that would reduce the noise and increase the maximum frequency it
could usefully amplify. From the data sheet, with 200v on anode and
grid 2 and an anode current of 6mA, the gm is about 6mA/V, which
gives an input impedance at the cathode of 160 ohms. A 75-ohm
feeder could be matched to this with a Pi tank or by tapping the L
or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in
grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best
noise figure). If I also use an EF91 as a mixer, I might need one
more stage of RF gain to get the signal up to a level where the
mixer noise is negligible - but this isn't such a bad thing because
it would allow extra tuned circuits to give better image rejection
and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up
on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as
the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it
happens to lie at a frequency where the dipole has another resonance
or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the
aerial (the sleeve dipole has a 'cold' bottom end and could be joined
directly onto the converter box). The HT and LT could be supplied
either by a separate multi-core cable or by superimposing 40v A.C. at
50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a
mains transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v
or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect
- will be able to assist you very much in this endeavour. However,
there should be tons of info on this in one of the old ARRL handbooks.
If you have any from the early 60s lying around it should be well worth
a look through.
I have read most of that sort of literature in the past and still have >copies of most of it but don't remember this particular approach being
used before - that was why I though it might make a good fun project.
There are some grounded-grid circuits but they use triodes intended for
the purpose. There are cascode circuits with double (and sometimes two >single) triodes but, again, the triodes are intended for that purpose.
The idea of using a bog-standard descendent of the ubiquitous EF50 for >frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a >triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the >wideband front end of a noise-measuring set that I designed; it gave very >satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact -
comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
I know a lot of receiver designers, and the older ones are all Hams.
Joe
+1
That's where all the expertise is. Esp. with tubes.
Tubes are noisy. There are MMICS with NFs below 1 dB.
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres >>>>>> (144 Mc/s) and I have thought about making a sleeve dipole for that >>>>>> band. My VHF receiver is an Eddystone 770R, which covers the band >>>>>> but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled >>>>>> down-converter, that would allow me to use an HF communications
receiver or the lower ranges of the 770R, so that the band 2 Mc/s >>>>>> wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I >>>>>> thought I might have a go at making a down-converter using valves - >>>>>> but not necessarily the expensive 'cult' ones which everyone seems >>>>>> to regard as having magical powers. The EF91 is plentiful and
cheap as New Old Stock, so that seems like a good valve to start >>>>>> playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad >>>>>> a noise figure (although Mullard don't quote one in their data
sheet). If I triode-strapped it and ran it in grounded grid mode, >>>>>> that would reduce the noise and increase the maximum frequency it >>>>>> could usefully amplify. From the data sheet, with 200v on anode and >>>>>> grid 2 and an anode current of 6mA, the gm is about 6mA/V, which >>>>>> gives an input impedance at the cathode of 160 ohms. A 75-ohm
feeder could be matched to this with a Pi tank or by tapping the L >>>>>> or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in
grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best >>>>>> noise figure). If I also use an EF91 as a mixer, I might need one >>>>>> more stage of RF gain to get the signal up to a level where the
mixer noise is negligible - but this isn't such a bad thing because >>>>>> it would allow extra tuned circuits to give better image rejection >>>>>> and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up >>>> on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as >>>> the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>> signal could be radiated by the aerial - especially if it happens to lie >>>> at a frequency where the dipole has another resonance or the dipole and >>>> downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>> (the sleeve dipole has a 'cold' bottom end and could be joined directly >>>> onto the converter box). The HT and LT could be supplied either by a >>>> separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>> co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>> 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL
handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group today who can really add any value here. Ham group, Liz; ham group.
2 metres is pretty much DC nowadays anyhow.
HF receivers don’t have to have good noise performance because the atmosphere is so noisy, and AFAICT they usually don’t. Intermod is more of an issue.
The atmosphere is quieter above 100 MHz, though, so you care more about the Rx noise figure.
A mixer front end is going to have a noise figure of 6 dB or so, on account of the conversion loss, and that adds to the NF of the HF back end.
Some gain ahead of the mixer, and some more following the band select
filter should help a lot. Don’t overdo it, of course.
Cursitor Doom <cd@notformail.com> wrote:
[...]
There's not a single person on this group today who can really add any
value here.
You do them a dis-service, there are some people here who can think with
an open mind. Even if the ideas they come up with wouldn't work, trying
to find out or explain why they wouldn't work is a good exercise and may
lead to a better solution than just asking hams what they have done
before.
On a sunny day (Sat, 9 Nov 2024 16:35:45 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r2rj8l.msi28f14weovyN%liz@poppyrecords.invalid.invalid>:
My current receiving aerial system is very inefficient at 2 metres (144 >>Mc/s) and I have thought about making a sleeve dipole for that band. My >>VHF receiver is an Eddystone 770R, which covers the band but only in a >>small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
Have you ever considered using a RTL_SDR stick and a PC or Raspberry
program for reception?
Something I wrote for it:
https://panteltje.nl/pub/xpsa-0.7.gif
those sticks cover from about 20 MHz to 1.6 GHz
More abou those here:
https://www.rtl-sdr.com/about-rtl-sdr/
even used one to receive GPS signals Those sticks are about 40? dollars
on ebay, accuracy 1 ppm.
https://www.ebay.com/itm/276000566513?
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>Stock, so that seems like a good valve to start playing about with.
I remember ECC85 in FM tuners, should be fine at 144 MHz:
https://www.radiomuseum.org/tubes/tube_ecc85.html
That circuit diagram shows an about 100 MHz to 10.7 MHz FM radio input
stage + mixer.
I have used that tube a few times.
But transistors took over, and now chips like in that RTL_SDR stick, are
hard to beat.
Sometimes I just strip some coax at the right length for antenna:
https://www.panteltje.nl/pub/DVB-T2_antenna_IXIMG_0757.JPG
Have some yagi antennas too, and even an old TV rack..
And a big 27 MHz GPA antenna somewhere...
On Sat, 9 Nov 2024 21:40:06 +0000, Liz Tuddenham wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
There's not a single person on this group today who can really add any
value here.
You do them a dis-service, there are some people here who can think with
an open mind. Even if the ideas they come up with wouldn't work, trying
to find out or explain why they wouldn't work is a good exercise and may
lead to a better solution than just asking hams what they have done
before.
OK, that's entirely your call. But I think you'll find the number of
people here with expertise in VHF receiver design is zero and the
proportion of those with an adequate familiarity with designing for toobz
is a vanishingly small subset of that figure. :)
On Sun, 10 Nov 2024 06:08:27 GMT, Jan Panteltje wrote:
On a sunny day (Sat, 9 Nov 2024 16:35:45 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r2rj8l.msi28f14weovyN%liz@poppyrecords.invalid.invalid>:
My current receiving aerial system is very inefficient at 2 metres (144 >>>Mc/s) and I have thought about making a sleeve dipole for that band. My >>>VHF receiver is an Eddystone 770R, which covers the band but only in a >>>small portion of the whole scale. While I am improvomg the aerial >>>system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges >>>of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>scale length.
Have you ever considered using a RTL_SDR stick and a PC or Raspberry
program for reception?
Something I wrote for it:
https://panteltje.nl/pub/xpsa-0.7.gif
those sticks cover from about 20 MHz to 1.6 GHz
More abou those here:
https://www.rtl-sdr.com/about-rtl-sdr/
even used one to receive GPS signals Those sticks are about 40? dollars
on ebay, accuracy 1 ppm.
https://www.ebay.com/itm/276000566513?
I'm sure Liz is aware there are far better modern alternatives out there, >Jan. However, this is (I believe) a purely fun project - and I've been >thinking for many years about doing a similar thing myself with tubes. In >fact I've retained a substantial collection of the damn things for
precisely this purpose. I always thought, 'one day I'll retire and I'll
have time to build something using these valves and it'll be a blast.' >Anyway, I retired 25 years ago and have even less time now for fun
projects than I had when I was working. Such is life...
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but >>>not necessarily the expensive 'cult' ones which everyone seems to regard >>>as having magical powers. The EF91 is plentiful and cheap as New Old >>>Stock, so that seems like a good valve to start playing about with.
I remember ECC85 in FM tuners, should be fine at 144 MHz:
https://www.radiomuseum.org/tubes/tube_ecc85.html
That circuit diagram shows an about 100 MHz to 10.7 MHz FM radio input
stage + mixer.
I have used that tube a few times.
But transistors took over, and now chips like in that RTL_SDR stick, are
hard to beat.
Sometimes I just strip some coax at the right length for antenna:
https://www.panteltje.nl/pub/DVB-T2_antenna_IXIMG_0757.JPG
Have some yagi antennas too, and even an old TV rack..
And a big 27 MHz GPA antenna somewhere...
Dunno if you have any of the RSGB-published books by Pat Hawker (G3VA
IIRC) but he had several designs for very effective antennas at VHF and
UHF made from lengths of old coax. The emphasis was always on economical >designs with old Pat. He grew up in the shadow of WW2 where you had to
make do with what you found lying around in the rubble of bomb craters.
On a sunny day (Sun, 10 Nov 2024 10:14:47 -0000 (UTC)) it happened Cursitor >Doom <cd999666@notformail.com> wrote in <vgq12n$ao84$2@dont-email.me>:
On Sun, 10 Nov 2024 06:08:27 GMT, Jan Panteltje wrote:
On a sunny day (Sat, 9 Nov 2024 16:35:45 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r2rj8l.msi28f14weovyN%liz@poppyrecords.invalid.invalid>:
My current receiving aerial system is very inefficient at 2 metres (144 >>>>Mc/s) and I have thought about making a sleeve dipole for that band. My >>>>VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>small portion of the whole scale. While I am improvomg the aerial >>>>system, I could also make a crystal-controlled down-converter, that >>>>would allow me to use an HF communications receiver or the lower ranges >>>>of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>scale length.
Have you ever considered using a RTL_SDR stick and a PC or Raspberry
program for reception?
Something I wrote for it:
https://panteltje.nl/pub/xpsa-0.7.gif
those sticks cover from about 20 MHz to 1.6 GHz
More abou those here:
https://www.rtl-sdr.com/about-rtl-sdr/
even used one to receive GPS signals Those sticks are about 40? dollars
on ebay, accuracy 1 ppm.
https://www.ebay.com/itm/276000566513?
I'm sure Liz is aware there are far better modern alternatives out there, >>Jan. However, this is (I believe) a purely fun project - and I've been >>thinking for many years about doing a similar thing myself with tubes. In >>fact I've retained a substantial collection of the damn things for >>precisely this purpose. I always thought, 'one day I'll retire and I'll >>have time to build something using these valves and it'll be a blast.' >>Anyway, I retired 25 years ago and have even less time now for fun
projects than I had when I was working. Such is life...
When I had the teefee repair shop in Amsterdam in the seventies and early eighties
lots of partial tube sets for repair, tubes especially in the HV stuff, PD500 makes a nice x-ray source:
http://www.kronjaeger.com/hv-old/xray/tech/PD500/index.html
had plenty tubes in stock,
now I have zero tubes here...
When I started in broadcasting in 1968 more tubes in the studios than you can imagine,
https://www.historyofrecording.com/ampexvrx1000aniv.html
note the racks with tubes in the picture on the left.
It's been a few years since I designed anything with valves, so I >>>>thought I might have a go at making a down-converter using valves - but >>>>not necessarily the expensive 'cult' ones which everyone seems to regard >>>>as having magical powers. The EF91 is plentiful and cheap as New Old >>>>Stock, so that seems like a good valve to start playing about with.
I remember ECC85 in FM tuners, should be fine at 144 MHz:
https://www.radiomuseum.org/tubes/tube_ecc85.html
That circuit diagram shows an about 100 MHz to 10.7 MHz FM radio input
stage + mixer.
I have used that tube a few times.
But transistors took over, and now chips like in that RTL_SDR stick, are >>> hard to beat.
Sometimes I just strip some coax at the right length for antenna:
https://www.panteltje.nl/pub/DVB-T2_antenna_IXIMG_0757.JPG
Have some yagi antennas too, and even an old TV rack..
And a big 27 MHz GPA antenna somewhere...
Dunno if you have any of the RSGB-published books by Pat Hawker (G3VA
IIRC) but he had several designs for very effective antennas at VHF and
UHF made from lengths of old coax. The emphasis was always on economical >>designs with old Pat. He grew up in the shadow of WW2 where you had to
make do with what you found lying around in the rubble of bomb craters.
I had a RSGB book, and in 1964-1967 period used it to design all that ham radio stuff..
Very nice book, learned a lot from it.
In the seventies in the studios more all transistor stuff,
but still CRTs and film scanners with CRT to scan film with photo-multipliers for red green and blue,
Not to mention the whole video camera stuff I worked with, evolving from inconoscope to plumbicons to CDD.
Designed and build my own portable vidicon based TV camera in 1968, that gave me the broadcasting job basically.
And that camera ran on nicad battery and was all transistor.
We had nice electronic magazines too, 'Radio Electronica', 'Electuur' (Elector?)
and whatever I could get hands on in English.
Tubes are noisy. There are MMICS with NFs below 1 dB.
There are quiet valves (Nuvistors) and noisy transistors (many),
engineering is a matter of chosing the right ones or using them in a way which minimises the noise or makes it less significant in the overall
design.
On Sun, 10 Nov 2024 11:19:14 GMT, Jan Panteltje <alien@comet.invalid>...
wrote:
We had nice electronic magazines too, 'Radio Electronica', 'Electuur' (Elector?)
and whatever I could get hands on in English.
Elektor was one of the better hobby ones. I was also subscribed to
Wireless World which was a bit more heavy-duty.
No idea if any of
these are still being published and can't be bothered to find out.
There was also Everyday Electronics and Practical Electronics, too.
I'm guessing they've all gone now since the kids just want to code it
seems.
HF receivers don?t have to have good noise performance because the
atmosphere is so noisy, and AFAICT they usually don?t. Intermod is more of an issue.
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144 >>>>>>> Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>>> small portion of the whole scale. While I am improvomg the aerial >>>>>>> system, I could also make a crystal-controlled down-converter, that >>>>>>> would allow me to use an HF communications receiver or the lower ranges >>>>>>> of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>>> scale length.
It's been a few years since I designed anything with valves, so I >>>>>>> thought I might have a go at making a down-converter using valves - but >>>>>>> not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>>> Stock, so that seems like a good valve to start playing about with. >>>>>>>
The EF91 was used as an RF amplifier in the input stages of television >>>>>>> sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>>> (although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>>> the noise and increase the maximum frequency it could usefully amplify. >>>>>>> From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>>> cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>>> Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low >>>>>>> noise without instability problems or the dependence on neutralising >>>>>>> that a cascode stage would have (especially the need for correct >>>>>>> neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to >>>>>>> a level where the mixer noise is negligible - but this isn't such a bad >>>>>>> thing because it would allow extra tuned circuits to give better image >>>>>>> rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>>>> the downlead. If the down-converter is adjacent to the HF receiver, >>>>> there will be significant losses at VHF in the downlead, as the aerial >>>>> needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>> signal could be radiated by the aerial - especially if it happens to lie >>>>> at a frequency where the dipole has another resonance or the dipole and >>>>> downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>> (the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>> onto the converter box). The HT and LT could be supplied either by a >>>>> separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>> co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>> 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL
handbooks. If you have any from the early 60s lying around it should
be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group
today who can really add any value here. Ham group, Liz; ham group.
2 metres is pretty much DC nowadays anyhow.
HF receivers don’t have to have good noise performance because the atmosphere is so noisy, and AFAICT they usually don’t. Intermod is more of an issue.
The atmosphere is quieter above 100 MHz, though, so you care more about the Rx noise figure.
A mixer front end is going to have a noise figure of 6 dB or so, on account of the conversion loss, and that adds to the NF of the HF back end.
Some gain ahead of the mixer, and some more following the band select
filter should help a lot. Don’t overdo it, of course.
Cheers
Phil Hobbs
In article <1r2sqh1.puusef1eope1aN%liz@poppyrecords.invalid.invalid>, >liz@poppyrecords.invalid.invalid says...
Tubes are noisy. There are MMICS with NFs below 1 dB.
There are quiet valves (Nuvistors) and noisy transistors (many),
engineering is a matter of chosing the right ones or using them in a way
which minimises the noise or makes it less significant in the overall
design.
Once you get above say 100 MHz the tubes that are common do not have the >noise figure of very cheap solid state devices. A nuvistor at 150 MHz
will do good to prodce a noise figure of 3 dB. A cheap fet like a U310
will have a noise figure of less than 2 dB and the power supply will be
much cheaper to build. Going to cheap gasfets get you to under 1 dB of
noise figure. At this time I just do not see why anyone would want to
use tubes in a receiver above 50 MHz if they want a sensitive receiver.
Years ago I had an Ameco receive converter for 2 meters. It used
nuvistor tubes. Worked fine but I put a u310 fet preamp on it and it
was noticable beter.
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres
(144 Mc/s) and I have thought about making a sleeve dipole for that >> >> >> >band. My VHF receiver is an Eddystone 770R, which covers the band
but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled >> >> >> >down-converter, that would allow me to use an HF communications
receiver or the lower ranges of the 770R, so that the band 2 Mc/s
wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - >> >> >> >but not necessarily the expensive 'cult' ones which everyone seems
to regard as having magical powers. The EF91 is plentiful and
cheap as New Old Stock, so that seems like a good valve to start
playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad
a noise figure (although Mullard don't quote one in their data
sheet). If I triode-strapped it and ran it in grounded grid mode,
that would reduce the noise and increase the maximum frequency it
could usefully amplify. From the data sheet, with 200v on anode and >> >> >> >grid 2 and an anode current of 6mA, the gm is about 6mA/V, which
gives an input impedance at the cathode of 160 ohms. A 75-ohm
feeder could be matched to this with a Pi tank or by tapping the L
or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in
grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best
noise figure). If I also use an EF91 as a mixer, I might need one
more stage of RF gain to get the signal up to a level where the
mixer noise is negligible - but this isn't such a bad thing because >> >> >> >it would allow extra tuned circuits to give better image rejection
and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up
on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as
the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it
happens to lie at a frequency where the dipole has another resonance
or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the
aerial (the sleeve dipole has a 'cold' bottom end and could be joined
directly onto the converter box). The HT and LT could be supplied
either by a separate multi-core cable or by superimposing 40v A.C. at >> >> >50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a
mains transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v
or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect >> >> - will be able to assist you very much in this endeavour. However,
there should be tons of info on this in one of the old ARRL handbooks.
If you have any from the early 60s lying around it should be well worth >> >> a look through.
I have read most of that sort of literature in the past and still have
copies of most of it but don't remember this particular approach being
used before - that was why I though it might make a good fun project.
There are some grounded-grid circuits but they use triodes intended for
the purpose. There are cascode circuits with double (and sometimes two
single) triodes but, again, the triodes are intended for that purpose.
The idea of using a bog-standard descendent of the ubiquitous EF50 for
frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a
triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the
wideband front end of a noise-measuring set that I designed; it gave very >> >satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact -
comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
Series-tuned input circuit.
On 09/11/2024 22:52, Phil Hobbs wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>>>> small portion of the whole scale. While I am improvomg the aerial >>>>>>>> system, I could also make a crystal-controlled down-converter, that >>>>>>>> would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>>>> scale length.
It's been a few years since I designed anything with valves, so I >>>>>>>> thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>>>> Stock, so that seems like a good valve to start playing about with. >>>>>>>>
The EF91 was used as an RF amplifier in the input stages of television >>>>>>>> sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>>>> (although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>>>> the noise and increase the maximum frequency it could usefully amplify.
From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>>>> cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>>>> Pi tank or by tapping the L or the C of an input tumed circuit. >>>>>>>>
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low >>>>>>>> noise without instability problems or the dependence on neutralising >>>>>>>> that a cascode stage would have (especially the need for correct >>>>>>>> neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad
thing because it would allow extra tuned circuits to give better image >>>>>>>> rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >>>>>>>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>>>>> the downlead. If the down-converter is adjacent to the HF receiver, >>>>>> there will be significant losses at VHF in the downlead, as the aerial >>>>>> needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>>> signal could be radiated by the aerial - especially if it happens to lie >>>>>> at a frequency where the dipole has another resonance or the dipole and >>>>>> downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>>> (the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>>> onto the converter box). The HT and LT could be supplied either by a >>>>>> separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>>> co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>>> 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL >>>>> handbooks. If you have any from the early 60s lying around it should >>>>> be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group
today who can really add any value here. Ham group, Liz; ham group.
2 metres is pretty much DC nowadays anyhow.
HF receivers don’t have to have good noise performance because the
atmosphere is so noisy, and AFAICT they usually don’t. Intermod is more of >> an issue.
The atmosphere is quieter above 100 MHz, though, so you care more about the >> Rx noise figure.
A mixer front end is going to have a noise figure of 6 dB or so, on account >> of the conversion loss, and that adds to the NF of the HF back end.
Some gain ahead of the mixer, and some more following the band select
filter should help a lot. Don’t overdo it, of course.
Cheers
Phil Hobbs
Remarkably commutating switch mixer like diode rings etc can be made
almost lossless if the source and load impedances are manipulated right. >British ham Peter Martinez the inventor of varicode psk31 has shown that
if the mixer RF port is fed from a parallel tuned circuit and IF port
loaded with a series tuned circuit in the right ratio then the 6dB loss >always assumed to be unavoidable goes.
piglet
On Sun, 10 Nov 2024 08:00:17 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >> >> >> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres >> >> >> >(144 Mc/s) and I have thought about making a sleeve dipole for that >> >> >> >band. My VHF receiver is an Eddystone 770R, which covers the band >> >> >> >but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled >> >> >> >down-converter, that would allow me to use an HF communications
receiver or the lower ranges of the 770R, so that the band 2 Mc/s >> >> >> >wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I >> >> >> >thought I might have a go at making a down-converter using valves - >> >> >> >but not necessarily the expensive 'cult' ones which everyone seems >> >> >> >to regard as having magical powers. The EF91 is plentiful and
cheap as New Old Stock, so that seems like a good valve to start
playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad >> >> >> >a noise figure (although Mullard don't quote one in their data
sheet). If I triode-strapped it and ran it in grounded grid mode, >> >> >> >that would reduce the noise and increase the maximum frequency it >> >> >> >could usefully amplify. From the data sheet, with 200v on anode and >> >> >> >grid 2 and an anode current of 6mA, the gm is about 6mA/V, which
gives an input impedance at the cathode of 160 ohms. A 75-ohm
feeder could be matched to this with a Pi tank or by tapping the L >> >> >> >or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in
grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best
noise figure). If I also use an EF91 as a mixer, I might need one >> >> >> >more stage of RF gain to get the signal up to a level where the
mixer noise is negligible - but this isn't such a bad thing because >> >> >> >it would allow extra tuned circuits to give better image rejection >> >> >> >and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up >> >> >on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as >> >> >the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it >> >> >happens to lie at a frequency where the dipole has another resonance >> >> >or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the
aerial (the sleeve dipole has a 'cold' bottom end and could be joined >> >> >directly onto the converter box). The HT and LT could be supplied
either by a separate multi-core cable or by superimposing 40v A.C. at >> >> >50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a >> >> >mains transformer primary. The full primary winding would act as an >> >> >auto-transformer to give 250v H.T. and the secondary could give 6.3v >> >> >or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect >> >> - will be able to assist you very much in this endeavour. However,
there should be tons of info on this in one of the old ARRL handbooks. >> >> If you have any from the early 60s lying around it should be well worth >> >> a look through.
I have read most of that sort of literature in the past and still have
copies of most of it but don't remember this particular approach being
used before - that was why I though it might make a good fun project.
There are some grounded-grid circuits but they use triodes intended for >> >the purpose. There are cascode circuits with double (and sometimes two >> >single) triodes but, again, the triodes are intended for that purpose. >> >The idea of using a bog-standard descendent of the ubiquitous EF50 for
frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a
triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the >> >wideband front end of a noise-measuring set that I designed; it gave very >> >satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact -
comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
Series-tuned input circuit.
Or a parallel tank with taps. The Q killers are the radiation
resistance of the antenna and, a little bit, the ohmic component of
the grid impedance from electrons being ornery.
On 09/11/2024 22:52, Phil Hobbs wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 09 Nov 2024 12:21:41 -0800, john larkin <JL@gct.com> wrote:
On Sat, 09 Nov 2024 20:02:05 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a >>>>>>>> small portion of the whole scale. While I am improvomg the aerial >>>>>>>> system, I could also make a crystal-controlled down-converter, that >>>>>>>> would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater >>>>>>>> scale length.
It's been a few years since I designed anything with valves, so I >>>>>>>> thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >>>>>>>> Stock, so that seems like a good valve to start playing about with. >>>>>>>>
The EF91 was used as an RF amplifier in the input stages of television >>>>>>>> sets working at about 45 Mc/s, so it can't have too bad a noise figure >>>>>>>> (although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce >>>>>>>> the noise and increase the maximum frequency it could usefully amplify.
From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >>>>>>>> cathode of 160 ohms. A 75-ohm feeder could be matched to this with a >>>>>>>> Pi tank or by tapping the L or the C of an input tumed circuit. >>>>>>>>
The voltage gain may not be as high in this configuration as in grounded
cathode mode, but it allows the valve to be triode strapped for low >>>>>>>> noise without instability problems or the dependence on neutralising >>>>>>>> that a cascode stage would have (especially the need for correct >>>>>>>> neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad
thing because it would allow extra tuned circuits to give better image >>>>>>>> rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >>>>>>>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that atmospheric >>>>>>> noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up on >>>>>> the downlead. If the down-converter is adjacent to the HF receiver, >>>>>> there will be significant losses at VHF in the downlead, as the aerial >>>>>> needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local oscillator >>>>>> signal could be radiated by the aerial - especially if it happens to lie >>>>>> at a frequency where the dipole has another resonance or the dipole and >>>>>> downlead form a resonant system.
I was thinking in terms of the converter being right next to the aerial >>>>>> (the sleeve dipole has a 'cold' bottom end and could be joined directly >>>>>> onto the converter box). The HT and LT could be supplied either by a >>>>>> separate multi-core cable or by superimposing 40v A.C. at 50c/s on the >>>>>> co-ax and feeding it into the 200-220-240v tappings.of a mains
transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v or >>>>>> 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due
respect - will be able to assist you very much in this endeavour.
However, there should be tons of info on this in one of the old ARRL >>>>> handbooks. If you have any from the early 60s lying around it should >>>>> be well worth a look through.
I was never interested in rag chewing, but signals is still signals.
Indeed, but this is niche and there are so many fine points and
trade-offs and gotchas that need to be factored in that only a
dedicated VHF RF designer could assist here. For sure the best people
here could come up with a workable design, but in practice it would
stink for the above reasons. There's not a single person on this group
today who can really add any value here. Ham group, Liz; ham group.
2 metres is pretty much DC nowadays anyhow.
HF receivers don’t have to have good noise performance because the
atmosphere is so noisy, and AFAICT they usually don’t. Intermod is more of >> an issue.
The atmosphere is quieter above 100 MHz, though, so you care more about the >> Rx noise figure.
A mixer front end is going to have a noise figure of 6 dB or so, on account >> of the conversion loss, and that adds to the NF of the HF back end.
Some gain ahead of the mixer, and some more following the band select
filter should help a lot. Don’t overdo it, of course.
Cheers
Phil Hobbs
Remarkably commutating switch mixer like diode rings etc can be made
almost lossless if the source and load impedances are manipulated right. >British ham Peter Martinez the inventor of varicode psk31 has shown that
if the mixer RF port is fed from a parallel tuned circuit and IF port
loaded with a series tuned circuit in the right ratio then the 6dB loss >always assumed to be unavoidable goes.
On a sunny day (Sun, 10 Nov 2024 13:38:31 +0000) it happened Cursitor Doom ><cd@notformail.com> wrote in <eld1jjl15hq8ohgm3kifpodkktupt1lr3g@4ax.com>:
On Sun, 10 Nov 2024 11:19:14 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:...
We had nice electronic magazines too, 'Radio Electronica', 'Electuur' (Elector?)
and whatever I could get hands on in English.
Elektor was one of the better hobby ones. I was also subscribed to
Wireless World which was a bit more heavy-duty.
Yes I used to read that on occasion (if I did see it at the newsstand at the staion for example)
plus some German electronic related magazines,
No idea if any of
these are still being published and can't be bothered to find out.
There was also Everyday Electronics and Practical Electronics, too.
I'm guessing they've all gone now since the kids just want to code it >>seems.
Na, there is still a lot around on hardware design / building stuff, several websites.
Just google works great too.
Electronics is used in a very wide field...
Just got a new alu housing with fan for my raspi 4 8 GB (this one I use to post this)
It has an IR camera connected too (mlx90640_FLIR),
now to find a way to get the i2c and power lines to that IR camera module
out of that housing...
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices >are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
On a sunny day (Sun, 10 Nov 2024 09:51:49 -0000 (UTC)) it happened Cursitor Doom <cd999666@notformail.com> wrote in <vgpvnk$ao84$1@dont-email.me>:
On Sat, 9 Nov 2024 21:40:06 +0000, Liz Tuddenham wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
There's not a single person on this group today who can really add any >>>> value here.
You do them a dis-service, there are some people here who can think with >>> an open mind. Even if the ideas they come up with wouldn't work, trying >>> to find out or explain why they wouldn't work is a good exercise and may >>> lead to a better solution than just asking hams what they have done
before.
OK, that's entirely your call. But I think you'll find the number of
people here with expertise in VHF receiver design is zero and the >>proportion of those with an adequate familiarity with designing for toobz >>is a vanishingly small subset of that figure. :)
I designed plenty of VHF rx stuff, teefee works in that range,
including UHF.
But to go back in time and do it with toobs? No, I used transistors.
Only case I could think of for using toobs is when all semi-conductors
were destroyed by radiation.
But not much would be on air to listen for in that case.
And in that case shortwave would be a better place to listen for remaining lifeforms.
And grounded grid does not make a lot of sense, has not many advantages for a VHF input stage.
john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 08:00:17 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid >> >> >> >> (Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres >> >> >> >> >(144 Mc/s) and I have thought about making a sleeve dipole for that
band. My VHF receiver is an Eddystone 770R, which covers the band >> >> >> >> >but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled
down-converter, that would allow me to use an HF communications
receiver or the lower ranges of the 770R, so that the band 2 Mc/s >> >> >> >> >wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I >> >> >> >> >thought I might have a go at making a down-converter using valves -
but not necessarily the expensive 'cult' ones which everyone seems >> >> >> >> >to regard as having magical powers. The EF91 is plentiful and
cheap as New Old Stock, so that seems like a good valve to start >> >> >> >> >playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad >> >> >> >> >a noise figure (although Mullard don't quote one in their data
sheet). If I triode-strapped it and ran it in grounded grid mode, >> >> >> >> >that would reduce the noise and increase the maximum frequency it >> >> >> >> >could usefully amplify. From the data sheet, with 200v on anode and
grid 2 and an anode current of 6mA, the gm is about 6mA/V, which >> >> >> >> >gives an input impedance at the cathode of 160 ohms. A 75-ohm
feeder could be matched to this with a Pi tank or by tapping the L >> >> >> >> >or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in
grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best >> >> >> >> >noise figure). If I also use an EF91 as a mixer, I might need one >> >> >> >> >more stage of RF gain to get the signal up to a level where the
mixer noise is negligible - but this isn't such a bad thing because
it would allow extra tuned circuits to give better image rejection >> >> >> >> >and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >> >> >> >>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up >> >> >> >on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as >> >> >> >the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it >> >> >> >happens to lie at a frequency where the dipole has another resonance >> >> >> >or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the
aerial (the sleeve dipole has a 'cold' bottom end and could be joined >> >> >> >directly onto the converter box). The HT and LT could be supplied
either by a separate multi-core cable or by superimposing 40v A.C. at
50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a >> >> >> >mains transformer primary. The full primary winding would act as an >> >> >> >auto-transformer to give 250v H.T. and the secondary could give 6.3v >> >> >> >or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect
- will be able to assist you very much in this endeavour. However,
there should be tons of info on this in one of the old ARRL handbooks. >> >> >> If you have any from the early 60s lying around it should be well worth
a look through.
I have read most of that sort of literature in the past and still have >> >> >copies of most of it but don't remember this particular approach being >> >> >used before - that was why I though it might make a good fun project.
There are some grounded-grid circuits but they use triodes intended for >> >> >the purpose. There are cascode circuits with double (and sometimes two >> >> >single) triodes but, again, the triodes are intended for that purpose. >> >> >The idea of using a bog-standard descendent of the ubiquitous EF50 for >> >> >frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a
triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the >> >> >wideband front end of a noise-measuring set that I designed; it gave very
satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact -
comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
Series-tuned input circuit.
Or a parallel tank with taps. The Q killers are the radiation
resistance of the antenna and, a little bit, the ohmic component of
the grid impedance from electrons being ornery.
The point I was making about grounded-grid operation is that the input >impedance of the valve is very nearly the characteristic impedance of
the co-ax (voltage ratio 3:2 for a triode-strapped EF91 drawing 6mA from
a 200V HT line). A Pi network or a 3:2 winding on a ferrite core could
be used to match them
On Sun, 10 Nov 2024 16:03:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 08:00:17 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid >>> >> >> (Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres
(144 Mc/s) and I have thought about making a sleeve dipole for that
band. My VHF receiver is an Eddystone 770R, which covers the band
but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled
down-converter, that would allow me to use an HF communications >>> >> >> >> >receiver or the lower ranges of the 770R, so that the band 2 Mc/s
wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I >>> >> >> >> >thought I might have a go at making a down-converter using valves -
but not necessarily the expensive 'cult' ones which everyone seems
to regard as having magical powers. The EF91 is plentiful and >>> >> >> >> >cheap as New Old Stock, so that seems like a good valve to start >>> >> >> >> >playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad
a noise figure (although Mullard don't quote one in their data >>> >> >> >> >sheet). If I triode-strapped it and ran it in grounded grid mode,
that would reduce the noise and increase the maximum frequency it >>> >> >> >> >could usefully amplify. From the data sheet, with 200v on anode and
grid 2 and an anode current of 6mA, the gm is about 6mA/V, which >>> >> >> >> >gives an input impedance at the cathode of 160 ohms. A 75-ohm >>> >> >> >> >feeder could be matched to this with a Pi tank or by tapping the L
or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in >>> >> >> >> >grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best >>> >> >> >> >noise figure). If I also use an EF91 as a mixer, I might need one
more stage of RF gain to get the signal up to a level where the >>> >> >> >> >mixer noise is negligible - but this isn't such a bad thing because
it would allow extra tuned circuits to give better image rejection
and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >>> >> >> >>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF
receiver is almost certain to suffer from strong HF signals picked up
on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as
the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it >>> >> >> >happens to lie at a frequency where the dipole has another resonance >>> >> >> >or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the
aerial (the sleeve dipole has a 'cold' bottom end and could be joined
directly onto the converter box). The HT and LT could be supplied >>> >> >> >either by a separate multi-core cable or by superimposing 40v A.C. at
50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a
mains transformer primary. The full primary winding would act as an >>> >> >> >auto-transformer to give 250v H.T. and the secondary could give 6.3v >>> >> >> >or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect
- will be able to assist you very much in this endeavour. However, >>> >> >> there should be tons of info on this in one of the old ARRL handbooks.
If you have any from the early 60s lying around it should be well worth
a look through.
I have read most of that sort of literature in the past and still have >>> >> >copies of most of it but don't remember this particular approach being >>> >> >used before - that was why I though it might make a good fun project. >>> >> >There are some grounded-grid circuits but they use triodes intended for >>> >> >the purpose. There are cascode circuits with double (and sometimes two >>> >> >single) triodes but, again, the triodes are intended for that purpose. >>> >> >The idea of using a bog-standard descendent of the ubiquitous EF50 for >>> >> >frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a
triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the >>> >> >wideband front end of a noise-measuring set that I designed; it gave very
satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact -
comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
Series-tuned input circuit.
Or a parallel tank with taps. The Q killers are the radiation
resistance of the antenna and, a little bit, the ohmic component of
the grid impedance from electrons being ornery.
The point I was making about grounded-grid operation is that the input >>impedance of the valve is very nearly the characteristic impedance of
the co-ax (voltage ratio 3:2 for a triode-strapped EF91 drawing 6mA from
a 200V HT line). A Pi network or a 3:2 winding on a ferrite core could
be used to match them
A tuned circuit into the grid has voltage gain, but the grounded-grid
with ohmic matched impedance throws away at least half the available
signal voltage. Impedance matching isn't good when it throws away
signal.
It's the voltage difference between the grid and cathode that gets
amplified against the tube's inherent noise.
Of course you can never get a better s/n than what the antenna
provides, and that will be pretty bad, so working hard to get a very
low noise fig in a HF receiver is entertaining but not terribly
useful.
At some wavelengths, in the microwave, looking at things way overhead
with a very directional antenna, low noise figures are worth the
hassle. The effective temperature of the universe is low.
A very directional antenna is a big win on s/n. It ignores a lot of
junk. I don't think it improves the inherent thermal background if
it's receiving terrestrial transmitters. That would violate COE.
I wonder if one can tell the difference in thermal noise by aiming an
antenna north or south from the USA or Europe. It's certainly less
aiming up.
I guess a good antenna feeding a matched resistive load will heat up
the load; steal power from the BBC. Or aim up and cool it.
On Sun, 10 Nov 2024 10:09:22 -0800, john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 16:03:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 08:00:17 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid >>>> >> (Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid >>>> >> >> (Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres
(144 Mc/s) and I have thought about making a sleeve dipole for that
band. My VHF receiver is an Eddystone 770R, which covers the band
but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled
down-converter, that would allow me to use an HF communications >>>> >> >> >> >receiver or the lower ranges of the 770R, so that the band 2 Mc/s
wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves -
but not necessarily the expensive 'cult' ones which everyone seems
to regard as having magical powers. The EF91 is plentiful and >>>> >> >> >> >cheap as New Old Stock, so that seems like a good valve to start >>>> >> >> >> >playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad
a noise figure (although Mullard don't quote one in their data >>>> >> >> >> >sheet). If I triode-strapped it and ran it in grounded grid mode,
that would reduce the noise and increase the maximum frequency it
could usefully amplify. From the data sheet, with 200v on anode and
grid 2 and an anode current of 6mA, the gm is about 6mA/V, which >>>> >> >> >> >gives an input impedance at the cathode of 160 ohms. A 75-ohm >>>> >> >> >> >feeder could be matched to this with a Pi tank or by tapping the L
or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in >>>> >> >> >> >grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best >>>> >> >> >> >noise figure). If I also use an EF91 as a mixer, I might need one
more stage of RF gain to get the signal up to a level where the >>>> >> >> >> >mixer noise is negligible - but this isn't such a bad thing because
it would allow extra tuned circuits to give better image rejection
and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >>>> >> >> >>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF >>>> >> >> >receiver is almost certain to suffer from strong HF signals picked up
on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as
the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it
happens to lie at a frequency where the dipole has another resonance
or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the >>>> >> >> >aerial (the sleeve dipole has a 'cold' bottom end and could be joined
directly onto the converter box). The HT and LT could be supplied >>>> >> >> >either by a separate multi-core cable or by superimposing 40v A.C. at
50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a
mains transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v
or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect
- will be able to assist you very much in this endeavour. However, >>>> >> >> there should be tons of info on this in one of the old ARRL handbooks.
If you have any from the early 60s lying around it should be well worth
a look through.
I have read most of that sort of literature in the past and still have >>>> >> >copies of most of it but don't remember this particular approach being >>>> >> >used before - that was why I though it might make a good fun project. >>>> >> >There are some grounded-grid circuits but they use triodes intended for
the purpose. There are cascode circuits with double (and sometimes two
single) triodes but, again, the triodes are intended for that purpose.
The idea of using a bog-standard descendent of the ubiquitous EF50 for >>>> >> >frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a >>>> >> >triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the
wideband front end of a noise-measuring set that I designed; it gave very
satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact - >>>> >> comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
Series-tuned input circuit.
Or a parallel tank with taps. The Q killers are the radiation
resistance of the antenna and, a little bit, the ohmic component of
the grid impedance from electrons being ornery.
The point I was making about grounded-grid operation is that the input >>>impedance of the valve is very nearly the characteristic impedance of
the co-ax (voltage ratio 3:2 for a triode-strapped EF91 drawing 6mA from >>>a 200V HT line). A Pi network or a 3:2 winding on a ferrite core could >>>be used to match them
A tuned circuit into the grid has voltage gain, but the grounded-grid
with ohmic matched impedance throws away at least half the available
signal voltage. Impedance matching isn't good when it throws away
signal.
It's the voltage difference between the grid and cathode that gets >>amplified against the tube's inherent noise.
Of course you can never get a better s/n than what the antenna
provides, and that will be pretty bad, so working hard to get a very
low noise fig in a HF receiver is entertaining but not terribly
useful.
At some wavelengths, in the microwave, looking at things way overhead
with a very directional antenna, low noise figures are worth the
hassle. The effective temperature of the universe is low.
A very directional antenna is a big win on s/n. It ignores a lot of
junk. I don't think it improves the inherent thermal background if
it's receiving terrestrial transmitters. That would violate COE.
I wonder if one can tell the difference in thermal noise by aiming an >>antenna north or south from the USA or Europe. It's certainly less
aiming up.
I guess a good antenna feeding a matched resistive load will heat up
the load; steal power from the BBC. Or aim up and cool it.
Under 5Mhz is where it gets particularly bad. 80m is often unusable.
On Sun, 10 Nov 2024 16:03:25 +0000, liz@poppyrecords.invalid.invalid[...]
(Liz Tuddenham) wrote:
The point I was making about grounded-grid operation is that the input >impedance of the valve is very nearly the characteristic impedance of
the co-ax (voltage ratio 3:2 for a triode-strapped EF91 drawing 6mA from
a 200V HT line). A Pi network or a 3:2 winding on a ferrite core could
be used to match them
A tuned circuit into the grid has voltage gain,
On Sun, 10 Nov 2024 18:14:33 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Sun, 10 Nov 2024 10:09:22 -0800, john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 16:03:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 08:00:17 +0000, liz@poppyrecords.invalid.invalid >>>>> (Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid >>>>> >> (Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid >>>>> >> >> (Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres
(144 Mc/s) and I have thought about making a sleeve dipole for that
band. My VHF receiver is an Eddystone 770R, which covers the band
but only in a small portion of the whole scale. While I am >>>>> >> >> >> >improvomg the aerial system, I could also make a crystal-controlled
down-converter, that would allow me to use an HF communications >>>>> >> >> >> >receiver or the lower ranges of the 770R, so that the band 2 Mc/s
wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves -
but not necessarily the expensive 'cult' ones which everyone seems
to regard as having magical powers. The EF91 is plentiful and >>>>> >> >> >> >cheap as New Old Stock, so that seems like a good valve to start
playing about with.
The EF91 was used as an RF amplifier in the input stages of >>>>> >> >> >> >television sets working at about 45 Mc/s, so it can't have too bad
a noise figure (although Mullard don't quote one in their data >>>>> >> >> >> >sheet). If I triode-strapped it and ran it in grounded grid mode,
that would reduce the noise and increase the maximum frequency it
could usefully amplify. From the data sheet, with 200v on anode and
grid 2 and an anode current of 6mA, the gm is about 6mA/V, which
gives an input impedance at the cathode of 160 ohms. A 75-ohm >>>>> >> >> >> >feeder could be matched to this with a Pi tank or by tapping the L
or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in >>>>> >> >> >> >grounded cathode mode, but it allows the valve to be triode >>>>> >> >> >> >strapped for low noise without instability problems or the >>>>> >> >> >> >dependence on neutralising that a cascode stage would have >>>>> >> >> >> >(especially the need for correct neutralising to obtain the best
noise figure). If I also use an EF91 as a mixer, I might need one
more stage of RF gain to get the signal up to a level where the >>>>> >> >> >> >mixer noise is negligible - but this isn't such a bad thing because
it would allow extra tuned circuits to give better image rejection
and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF >>>>> >> >> >receiver is almost certain to suffer from strong HF signals picked up
on the downlead. If the down-converter is adjacent to the HF >>>>> >> >> >receiver, there will be significant losses at VHF in the downlead, as
the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local >>>>> >> >> >oscillator signal could be radiated by the aerial - especially if it
happens to lie at a frequency where the dipole has another resonance
or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the >>>>> >> >> >aerial (the sleeve dipole has a 'cold' bottom end and could be joined
directly onto the converter box). The HT and LT could be supplied >>>>> >> >> >either by a separate multi-core cable or by superimposing 40v A.C. at
50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a
mains transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v
or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect
- will be able to assist you very much in this endeavour. However, >>>>> >> >> there should be tons of info on this in one of the old ARRL handbooks.
If you have any from the early 60s lying around it should be well worth
a look through.
I have read most of that sort of literature in the past and still have
copies of most of it but don't remember this particular approach being
used before - that was why I though it might make a good fun project. >>>>> >> >There are some grounded-grid circuits but they use triodes intended for
the purpose. There are cascode circuits with double (and sometimes two
single) triodes but, again, the triodes are intended for that purpose.
The idea of using a bog-standard descendent of the ubiquitous EF50 for
frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff >>>>> >> >Woodburn's design for the Eddystone Panoramic Display Unit, where a >>>>> >> >triode-strapped E180F is used as a grounded-grid untuned wideband >>>>> >> >front-end amplifier. I did copy that successfully with a ZTX450 as the
wideband front end of a noise-measuring set that I designed; it gave very
satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact - >>>>> >> comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low >>>>> >> value resistor, a Q killer.
Series-tuned input circuit.
Or a parallel tank with taps. The Q killers are the radiation
resistance of the antenna and, a little bit, the ohmic component of
the grid impedance from electrons being ornery.
The point I was making about grounded-grid operation is that the input >>>>impedance of the valve is very nearly the characteristic impedance of >>>>the co-ax (voltage ratio 3:2 for a triode-strapped EF91 drawing 6mA from >>>>a 200V HT line). A Pi network or a 3:2 winding on a ferrite core could >>>>be used to match them
A tuned circuit into the grid has voltage gain, but the grounded-grid >>>with ohmic matched impedance throws away at least half the available >>>signal voltage. Impedance matching isn't good when it throws away
signal.
It's the voltage difference between the grid and cathode that gets >>>amplified against the tube's inherent noise.
Of course you can never get a better s/n than what the antenna
provides, and that will be pretty bad, so working hard to get a very
low noise fig in a HF receiver is entertaining but not terribly
useful.
At some wavelengths, in the microwave, looking at things way overhead >>>with a very directional antenna, low noise figures are worth the
hassle. The effective temperature of the universe is low.
A very directional antenna is a big win on s/n. It ignores a lot of
junk. I don't think it improves the inherent thermal background if
it's receiving terrestrial transmitters. That would violate COE.
I wonder if one can tell the difference in thermal noise by aiming an >>>antenna north or south from the USA or Europe. It's certainly less
aiming up.
I guess a good antenna feeding a matched resistive load will heat up
the load; steal power from the BBC. Or aim up and cool it.
Under 5Mhz is where it gets particularly bad. 80m is often unusable.
Again, a very directional antenna will help a lot. I guess that's
tricky at 80m, but some sort of phased array with signal processing
would be interesting.
Hasn't cell phones and the internet made ham radio and shortwave
listening mostly obsolete? Are kids becoming hams?
"Jan Panteltje" <alien@comet.invalid> wrote in message news:vgq37s$oo9h$1@solani.org...
On a sunny day (Sun, 10 Nov 2024 09:51:49 -0000 (UTC)) it happened Cursitor >> Doom <cd999666@notformail.com> wrote in <vgpvnk$ao84$1@dont-email.me>:
On Sat, 9 Nov 2024 21:40:06 +0000, Liz Tuddenham wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
There's not a single person on this group today who can really add any >>>>> value here.
You do them a dis-service, there are some people here who can think with >>>> an open mind. Even if the ideas they come up with wouldn't work, trying >>>> to find out or explain why they wouldn't work is a good exercise and may >>>> lead to a better solution than just asking hams what they have done
before.
OK, that's entirely your call. But I think you'll find the number of >>>people here with expertise in VHF receiver design is zero and the >>>proportion of those with an adequate familiarity with designing for toobz >>>is a vanishingly small subset of that figure. :)
I designed plenty of VHF rx stuff, teefee works in that range,
including UHF.
But to go back in time and do it with toobs? No, I used transistors.
Only case I could think of for using toobs is when all semi-conductors
were destroyed by radiation.
But not much would be on air to listen for in that case.
And in that case shortwave would be a better place to listen for remaining lifeforms.
And grounded grid does not make a lot of sense, has not many advantages for a VHF input stage.
Why?
https://www.google.com/search?&q=valve+fm+tuner&udm=2
I can see at least two grounded grids and I don't recall a transistor FM tuner without a grounded base first stage.
Reduced sensitivity was ofted caused by a need to replace that transistor because being the first stage it gets what the antenna
On Sun, 10 Nov 2024 14:33:41 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On a sunny day (Sun, 10 Nov 2024 13:38:31 +0000) it happened Cursitor Doom >><cd@notformail.com> wrote in <eld1jjl15hq8ohgm3kifpodkktupt1lr3g@4ax.com>:
On Sun, 10 Nov 2024 11:19:14 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:...
We had nice electronic magazines too, 'Radio Electronica', 'Electuur' (Elector?)
and whatever I could get hands on in English.
Elektor was one of the better hobby ones. I was also subscribed to >>>Wireless World which was a bit more heavy-duty.
Yes I used to read that on occasion (if I did see it at the newsstand at the staion for example)
plus some German electronic related magazines,
No idea if any of
these are still being published and can't be bothered to find out.
There was also Everyday Electronics and Practical Electronics, too.
I'm guessing they've all gone now since the kids just want to code it >>>seems.
Na, there is still a lot around on hardware design / building stuff, several websites.
Just google works great too.
Electronics is used in a very wide field...
Just got a new alu housing with fan for my raspi 4 8 GB (this one I use to post this)
It has an IR camera connected too (mlx90640_FLIR),
now to find a way to get the i2c and power lines to that IR camera module >>out of that housing...
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices
are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
Arduinos are very cheap and don't have all the overhead the Pi has in
terms of video capabilities. Plus they're piss-easy to program.
A Pi 5 plus accessories for 120 bux doesn't sound bad at all, though.
Or if you're really that much of a skinflint, you could consider PIC >programming. :-)
On Sun, 10 Nov 2024 10:09:22 -0800, john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 16:03:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sun, 10 Nov 2024 08:00:17 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 20:26:18 +0000, liz@poppyrecords.invalid.invalid >>>> >> (Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 9 Nov 2024 19:27:13 +0000, liz@poppyrecords.invalid.invalid >>>> >> >> (Liz Tuddenham) wrote:
john larkin <JL@gct.com> wrote:
On Sat, 9 Nov 2024 16:35:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
My current receiving aerial system is very inefficient at 2 metres
(144 Mc/s) and I have thought about making a sleeve dipole for that
band. My VHF receiver is an Eddystone 770R, which covers the band
but only in a small portion of the whole scale. While I am
improvomg the aerial system, I could also make a crystal-controlled
down-converter, that would allow me to use an HF communications >>>> >> >> >> >receiver or the lower ranges of the 770R, so that the band 2 Mc/s
wide would cover a much greater scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves -
but not necessarily the expensive 'cult' ones which everyone seems
to regard as having magical powers. The EF91 is plentiful and >>>> >> >> >> >cheap as New Old Stock, so that seems like a good valve to start >>>> >> >> >> >playing about with.
The EF91 was used as an RF amplifier in the input stages of
television sets working at about 45 Mc/s, so it can't have too bad
a noise figure (although Mullard don't quote one in their data >>>> >> >> >> >sheet). If I triode-strapped it and ran it in grounded grid mode,
that would reduce the noise and increase the maximum frequency it
could usefully amplify. From the data sheet, with 200v on anode and
grid 2 and an anode current of 6mA, the gm is about 6mA/V, which >>>> >> >> >> >gives an input impedance at the cathode of 160 ohms. A 75-ohm >>>> >> >> >> >feeder could be matched to this with a Pi tank or by tapping the L
or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in >>>> >> >> >> >grounded cathode mode, but it allows the valve to be triode
strapped for low noise without instability problems or the
dependence on neutralising that a cascode stage would have
(especially the need for correct neutralising to obtain the best >>>> >> >> >> >noise figure). If I also use an EF91 as a mixer, I might need one
more stage of RF gain to get the signal up to a level where the >>>> >> >> >> >mixer noise is negligible - but this isn't such a bad thing because
it would allow extra tuned circuits to give better image rejection
and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves? >>>> >> >> >>
How about a tube/valve XO and a diode mixer to start?
A good HF receiver may have a low enough noise figure that
atmospheric noise still dominates.
Good thinking but there are several snags with that system:
If the down-converter is at the aerial end of the feeder, the HF >>>> >> >> >receiver is almost certain to suffer from strong HF signals picked up
on the downlead. If the down-converter is adjacent to the HF
receiver, there will be significant losses at VHF in the downlead, as
the aerial needs to be mounted as high as possible.
If there is no amplifier ahead of the mixing diode, the local
oscillator signal could be radiated by the aerial - especially if it
happens to lie at a frequency where the dipole has another resonance
or the dipole and downlead form a resonant system.
I was thinking in terms of the converter being right next to the >>>> >> >> >aerial (the sleeve dipole has a 'cold' bottom end and could be joined
directly onto the converter box). The HT and LT could be supplied >>>> >> >> >either by a separate multi-core cable or by superimposing 40v A.C. at
50c/s on the co-ax and feeding it into the 200-220-240v tappings.of a
mains transformer primary. The full primary winding would act as an
auto-transformer to give 250v H.T. and the secondary could give 6.3v
or 12.6v to run the heaters.
This is really ham territory so I don't think JL - with all due respect
- will be able to assist you very much in this endeavour. However, >>>> >> >> there should be tons of info on this in one of the old ARRL handbooks.
If you have any from the early 60s lying around it should be well worth
a look through.
I have read most of that sort of literature in the past and still have >>>> >> >copies of most of it but don't remember this particular approach being >>>> >> >used before - that was why I though it might make a good fun project. >>>> >> >There are some grounded-grid circuits but they use triodes intended for
the purpose. There are cascode circuits with double (and sometimes two
single) triodes but, again, the triodes are intended for that purpose.
The idea of using a bog-standard descendent of the ubiquitous EF50 for >>>> >> >frequencies it wasn't supposed to cover - and making it do that
adequately - appealed to me.
The only place I have come across anything like this is in Geoff
Woodburn's design for the Eddystone Panoramic Display Unit, where a >>>> >> >triode-strapped E180F is used as a grounded-grid untuned wideband
front-end amplifier. I did copy that successfully with a ZTX450 as the
wideband front end of a noise-measuring set that I designed; it gave very
satisfactory results.
Seems to me that the lowest noise voltage gain - no noise in fact - >>>> >> comes from a high-Q LC resonator. And that best drives a small
capacitance like a grid.
Driving a cathode can be wideband, but a cathode looks like a low
value resistor, a Q killer.
Series-tuned input circuit.
Or a parallel tank with taps. The Q killers are the radiation
resistance of the antenna and, a little bit, the ohmic component of
the grid impedance from electrons being ornery.
The point I was making about grounded-grid operation is that the input >>>impedance of the valve is very nearly the characteristic impedance of
the co-ax (voltage ratio 3:2 for a triode-strapped EF91 drawing 6mA from >>>a 200V HT line). A Pi network or a 3:2 winding on a ferrite core could >>>be used to match them
A tuned circuit into the grid has voltage gain, but the grounded-grid
with ohmic matched impedance throws away at least half the available
signal voltage. Impedance matching isn't good when it throws away
signal.
It's the voltage difference between the grid and cathode that gets >>amplified against the tube's inherent noise.
Of course you can never get a better s/n than what the antenna
provides, and that will be pretty bad, so working hard to get a very
low noise fig in a HF receiver is entertaining but not terribly
useful.
At some wavelengths, in the microwave, looking at things way overhead
with a very directional antenna, low noise figures are worth the
hassle. The effective temperature of the universe is low.
A very directional antenna is a big win on s/n. It ignores a lot of
junk. I don't think it improves the inherent thermal background if
it's receiving terrestrial transmitters. That would violate COE.
I wonder if one can tell the difference in thermal noise by aiming an >>antenna north or south from the USA or Europe. It's certainly less
aiming up.
I guess a good antenna feeding a matched resistive load will heat up
the load; steal power from the BBC. Or aim up and cool it.
Under 5Mhz is where it gets particularly bad. 80m is often unusable.
My current receiving aerial system is very inefficient at 2 metres (144
Mc/s) and I have thought about making a sleeve dipole for that band. My
VHF receiver is an Eddystone 770R, which covers the band but only in a
small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old
Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure >(although Mullard don't quote one in their data sheet). If I
triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify.
From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the
cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct
neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad
thing because it would allow extra tuned circuits to give better image >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
In message <1r2rj8l.msi28f14weovyN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> writes
My current receiving aerial system is very inefficient at 2 metres (144 >Mc/s) and I have thought about making a sleeve dipole for that band. My >VHF receiver is an Eddystone 770R, which covers the band but only in a >small portion of the whole scale. While I am improvomg the aerial
system, I could also make a crystal-controlled down-converter, that
would allow me to use an HF communications receiver or the lower ranges
of the 770R, so that the band 2 Mc/s wide would cover a much greater
scale length.
It's been a few years since I designed anything with valves, so I
thought I might have a go at making a down-converter using valves - but
not necessarily the expensive 'cult' ones which everyone seems to regard
as having magical powers. The EF91 is plentiful and cheap as New Old >Stock, so that seems like a good valve to start playing about with.
The EF91 was used as an RF amplifier in the input stages of television
sets working at about 45 Mc/s, so it can't have too bad a noise figure >(although Mullard don't quote one in their data sheet). If I >triode-strapped it and ran it in grounded grid mode, that would reduce
the noise and increase the maximum frequency it could usefully amplify. >From the data sheet, with 200v on anode and grid 2 and an anode current
of 6mA, the gm is about 6mA/V, which gives an input impedance at the >cathode of 160 ohms. A 75-ohm feeder could be matched to this with a
Pi tank or by tapping the L or the C of an input tumed circuit.
The voltage gain may not be as high in this configuration as in grounded >cathode mode, but it allows the valve to be triode strapped for low
noise without instability problems or the dependence on neutralising
that a cascode stage would have (especially the need for correct >neutralising to obtain the best noise figure). If I also use an EF91 as
a mixer, I might need one more stage of RF gain to get the signal up to
a level where the mixer noise is negligible - but this isn't such a bad >thing because it would allow extra tuned circuits to give better image >rejection and allow a lower output frquency if I wanted one.
Anyone with experience of doing something like this with valves?
I built a 2metre down converter in 1971. It used an E88CC ( gold pins!) cascode grounded grid front end followed by an ECC81 mixer. Another
ECC81 was used as xtal Local Oscillator/multiplier.
I still have it.
The design was in UK publication Practical Wireless. I had quick look on World Radio History to see if I could find it , but no joy. Similar
designs might be available.
On a sunny day (Sun, 10 Nov 2024 17:39:36 +0000) it happened Cursitor Doom ><cd@notformail.com> wrote in <qpr1jj9glcibtukfkhsgt3m0ujq0kkho0l@4ax.com>:
On Sun, 10 Nov 2024 14:33:41 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On a sunny day (Sun, 10 Nov 2024 13:38:31 +0000) it happened Cursitor Doom >>><cd@notformail.com> wrote in <eld1jjl15hq8ohgm3kifpodkktupt1lr3g@4ax.com>: >>>
On Sun, 10 Nov 2024 11:19:14 GMT, Jan Panteltje <alien@comet.invalid> >>>>wrote:...
We had nice electronic magazines too, 'Radio Electronica', 'Electuur' (Elector?)
and whatever I could get hands on in English.
Elektor was one of the better hobby ones. I was also subscribed to >>>>Wireless World which was a bit more heavy-duty.
Yes I used to read that on occasion (if I did see it at the newsstand at the staion for example)
plus some German electronic related magazines,
No idea if any of
these are still being published and can't be bothered to find out. >>>>There was also Everyday Electronics and Practical Electronics, too.
I'm guessing they've all gone now since the kids just want to code it >>>>seems.
Na, there is still a lot around on hardware design / building stuff, several websites.
Just google works great too.
Electronics is used in a very wide field...
Just got a new alu housing with fan for my raspi 4 8 GB (this one I use to post this)
It has an IR camera connected too (mlx90640_FLIR),
now to find a way to get the i2c and power lines to that IR camera module >>>out of that housing...
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices
are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
Arduinos are very cheap and don't have all the overhead the Pi has in
terms of video capabilities. Plus they're piss-easy to program.
A Pi 5 plus accessories for 120 bux doesn't sound bad at all, though.
Or if you're really that much of a skinflint, you could consider PIC >>programming. :-)
I use this Pi 4 8 GB for web browsing, posting stuff here, spectrum analyzer, radio reception , music play, so much more
An arduno is something totally different.
But this 4 8GB is dead slow at times browsing the web.
Added a metal case with fan now to prevent it from throtling on over-temperature
so now its hovers around
temp=40.9'C
temp=41.3'C
temp=40.4'
..
Just cut and paste
Has a 4 TB Toshiba harddisc connected to it, some RTL-SDR stick, A huawei 4G stick so I have internet on it,
a HDMI monitor, and for all the other USB stuff a Sitecom USB hub, a Logitech wireless keyboard... and that IR FLIR camera on GPIO.
raspberrypi: ~ # df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root 30421240 27643352 1432704 96% /
devtmpfs 3879380 0 3879380 0% /dev
tmpfs 4044244 0 4044244 0% /dev/shm
tmpfs 1617700 1336 1616364 1% /run
tmpfs 5120 4 5116 1% /run/lock
/dev/mmcblk0p1 258095 50413 207682 20% /boot
tmpfs 808848 24 808824 1% /run/user/1000
/dev/sda2 3844420600 2863079020 785980916 79% /mnt/sda2
raspberrypi: ~ # top
top - 07:27:40 up 1 day, 22:12, 11 users, load average: 0.64, 0.66, 0.97 >Tasks: 221 total, 1 running, 220 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.8 us, 4.3 sy, 0.0 ni, 90.8 id, 0.1 wa, 0.0 hi, 0.1 si, 0.0 st
MiB Mem : 7898.9 total, 6529.0 free, 727.2 used, 642.7 buff/cache >MiB Swap: 100.0 total, 100.0 free, 0.0 used. 6853.9 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1105 root 19 -1 195056 77668 56360 S 10.2 1.0 195:49.13 Xorg
12594 root 20 0 980792 351696 161036 S 6.6 4.3 7:45.00 firefox-esr
12782 root 20 0 496732 164380 94644 S 3.9 2.0 2:14.18 Web Content
1123 root 20 0 48028 12892 8604 S 1.6 0.2 0:01.86 rxvt
1219 root 20 0 6644 4208 3832 S 1.6 0.1 37:20.43 xosview
12732 root 20 0 640868 135868 81320 S 1.3 1.7 1:02.58 WebExtensions
....
As to PIC programming, how about a simple oscilloscope with FFT option:
https://panteltje.nl/panteltje/pic/scope_pic/
from
https://panteltje.nl/panteltje/pic/index.html
Or controlling a drone:
https://panteltje.nl/panteltje/quadcopter/index.html
From:
https://panteltje.nl/panteltje/newsflex/download.html
and now show us somthing YOU designed, code YOU wrote, THAT WORKS!
And stop meddling here as if you are a censor, Billy blacklisting game with J Lurking
This is a non-moderated group, bring in some more content than boat anchors and show us!
!
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices
are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
Jan Panteltje <alien@comet.invalid> wrote:
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices
are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
I bought Raspberry Pi 1B when they appeared, but after that used
Chinese alternatives.
Orange Pi used to be cheap, most is more
expensive now. But Orange Pi Zero 3 is reasonably priced and
powerful enough for my purpose. You apparently want PC class machine,
for this I want real PC.
For light use mini-PCs may be enough and
are quite cheap. I got one for equvalent of $70, 6GB RAM, dual core
Celeron N3350, 64 GB solid state disc, 2 USB 3.0 slots (+ 2 USB 2.0),
LAN, Wifi, of course in case and with included power supply. For
me important advantage is that there is no fan (passive cooling only).
Less powerful used mini-PCs can be as cheap as equivalent of $5.
Supposedly some "TV boxes" are cheap, resonably powerful and can
be programmed with Linux. But I did not try one.
Pi-s are better for electronics/automation thanks to available
interfaces, but that needs much less compute power (camera is the
only high bandwidth interface that I use).
When you are satified
with lower compute power there are some cheap ones. I am trying
now Milkv Duo. Radxa ROCK also seem to be reasonably priced.
But once you want faster CPU, more RAM, EMMC, etc they are getting
more expensive. I am not sure why, memory modules for PC seem
to be cheaper than price of adding memory to SBC-s (possibly this
is just pure marketing).
On a sunny day (Sun, 17 Nov 2024 01:34:45 -0000 (UTC)) it happened antispam@fricas.org (Waldek Hebisch) wrote in <vhbh7j$26abk$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices
are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
I bought Raspberry Pi 1B when they appeared, but after that used
Chinese alternatives.
Same here, have some old Pi2 versions...
one Pi2 is on 24/7 running a server, measuring air pressure, radiation,
this Pi4 8 GB I use for web browsing and Usenet
a Pi4 4 GB records security cams and plays audio, records airplane traffic (with dump1090)
and lots more stuff...
Orange Pi used to be cheap, most is more
expensive now. But Orange Pi Zero 3 is reasonably priced and
powerful enough for my purpose. You apparently want PC class machine,
for this I want real PC.
I have several 'real' PCs.. but those are big and use a lot of power, have DVD burner, huge harddisks,
Almost never on these days, stopped burning optical disks, almost all USB harddisks for data storage now.
For light use mini-PCs may be enough and
are quite cheap. I got one for equvalent of $70, 6GB RAM, dual core >>Celeron N3350, 64 GB solid state disc, 2 USB 3.0 slots (+ 2 USB 2.0),
LAN, Wifi, of course in case and with included power supply. For
me important advantage is that there is no fan (passive cooling only).
Less powerful used mini-PCs can be as cheap as equivalent of $5.
Sound good, x86 based is nice too, have written lotd of stuff for that
Supposedly some "TV boxes" are cheap, resonably powerful and can
be programmed with Linux. But I did not try one.
Indeed, I have several satellite reception boxes, HD recording and playback no problem with those
some have internet connection too, record to USB SD stick.
When full with stuff I like to keep I copy it to a 4 TB Toshiba USB harddisk connected to my Pi4 8 GB.
I do have a satellite reception PCI card in an old x86 PC too, but that is not HD.
But wrote a lot of software for it.
Pi-s are better for electronics/automation thanks to available
interfaces, but that needs much less compute power (camera is the
only high bandwidth interface that I use).
Yes, GPIO is nice, on the PCs I uses the parport for I/O,
even specifically bought a parport PCI card for that on ebay..
Much goes via ethernet these days and that works fine on Rspberry too. Building / designing things with ethernet interface is not that hard.
severl projects on my site:
https://panteltje.nl/panteltje/newsflex/download.html
USB is also fast enough for many things.
When you are satified
with lower compute power there are some cheap ones. I am trying
now Milkv Duo. Radxa ROCK also seem to be reasonably priced.
But once you want faster CPU, more RAM, EMMC, etc they are getting
more expensive. I am not sure why, memory modules for PC seem
to be cheaper than price of adding memory to SBC-s (possibly this
is just pure marketing).
Yes, a lot of marketing is involved
You get sort of addicted to GPIO with Raspberries...
Anyways how much processing power do I really need?
I program a lot of stuff in asm for Microchip PICs:
https://panteltje.nl/panteltje/pic/index.html
This world creates bloat sftware so it can sell new hardware, Microsoft has shares in hardware companies,
so new bloat needs new hardware.. more money
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 17 Nov 2024 01:34:45 -0000 (UTC)) it happened
antispam@fricas.org (Waldek Hebisch) wrote in
<vhbh7j$26abk$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
What bothers me today (thought maybe use an extra Raspberry Pi) is that prices
are going up to insane lavels for a Raspi5 8 Gb + supply + housing + sdcard to above 120 USD:
https://www.sossolutions.nl/raspberry-pi-5-8gb-starter-kit-compleet
For just a bit more you have a decent mini computer:
https://www.aliexpress.com/w/wholesale-mini-pc-x86.html
Inflation?
Time to end raspi stuff and look for other solutions.
I bought Raspberry Pi 1B when they appeared, but after that used
Chinese alternatives.
Same here, have some old Pi2 versions...
one Pi2 is on 24/7 running a server, measuring air pressure, radiation,
this Pi4 8 GB I use for web browsing and Usenet
a Pi4 4 GB records security cams and plays audio, records airplane traffic (with dump1090)
and lots more stuff...
Orange Pi used to be cheap, most is more
expensive now. But Orange Pi Zero 3 is reasonably priced and
powerful enough for my purpose. You apparently want PC class machine, >>>for this I want real PC.
I have several 'real' PCs.. but those are big and use a lot of power, have DVD burner, huge harddisks,
Almost never on these days, stopped burning optical disks, almost all USB harddisks for data storage now.
I mostly depend on storing data on multiple HDD-s (my PC have mirrored
pair of discs and I have extra discs for backup). In last several years
I did not burn any DVD-s, but maybe I will do some with importand data
for extra safety (DVD are too small for bulk data).
I depend on data stored on HDD, most is fetched from Internert but
things vanish randomly from the net and I have my own indices of
interesting data, so I normally use local copy from my disk. Also,
have some compute intensive stuff.
For light use mini-PCs may be enough and
are quite cheap. I got one for equvalent of $70, 6GB RAM, dual core >>>Celeron N3350, 64 GB solid state disc, 2 USB 3.0 slots (+ 2 USB 2.0), >>>LAN, Wifi, of course in case and with included power supply. For
me important advantage is that there is no fan (passive cooling only). >>>Less powerful used mini-PCs can be as cheap as equivalent of $5.
Sound good, x86 based is nice too, have written lotd of stuff for that
Supposedly some "TV boxes" are cheap, resonably powerful and can
be programmed with Linux. But I did not try one.
Indeed, I have several satellite reception boxes, HD recording and playback no problem with those
some have internet connection too, record to USB SD stick.
When full with stuff I like to keep I copy it to a 4 TB Toshiba USB harddisk connected to my Pi4 8 GB.
I do have a satellite reception PCI card in an old x86 PC too, but that is not HD.
But wrote a lot of software for it.
Pi-s are better for electronics/automation thanks to available >>>interfaces, but that needs much less compute power (camera is the
only high bandwidth interface that I use).
Yes, GPIO is nice, on the PCs I uses the parport for I/O,
even specifically bought a parport PCI card for that on ebay..
Much goes via ethernet these days and that works fine on Rspberry too.
Building / designing things with ethernet interface is not that hard.
severl projects on my site:
https://panteltje.nl/panteltje/newsflex/download.html
USB is also fast enough for many things.
USB can do milliseconds, ethernet hundreds of microseconds, small
micros can do much better. Theoretically with a micro connected via USB
one can synchronize clocks of the micro and PC with microsecond
accuracy, I plan to try this but do not know how this will work.
When you are satified
with lower compute power there are some cheap ones. I am trying
now Milkv Duo. Radxa ROCK also seem to be reasonably priced.
But once you want faster CPU, more RAM, EMMC, etc they are getting
more expensive. I am not sure why, memory modules for PC seem
to be cheaper than price of adding memory to SBC-s (possibly this
is just pure marketing).
Yes, a lot of marketing is involved
You get sort of addicted to GPIO with Raspberries...
Anyways how much processing power do I really need?
I program a lot of stuff in asm for Microchip PICs:
https://panteltje.nl/panteltje/pic/index.html
Nice. I have avoided PICs, using now mostly STM32 and coding in C.
One can create quite small and efficient programs in C. I use
assembler when I feel it is better but currently that is mainly
for delay loop. Doing all in efficient assembler would be large
effort for moderate gain (maybe 20% efficiency/size improvement),
and IME "easy assembler" tend to be less efficient than C.
This world creates bloat sftware so it can sell new hardware, Microsoft has shares in hardware companies,
so new bloat needs new hardware.. more money
I dislike bloat but OTOH thanks to bloat powerful PC-s are available
at affordable price. Otherwise they would be an expensive industry/ >corporate items.
USB can do milliseconds, ethernet hundreds of microseconds, small
micros can do much better. Theoretically with a micro connected via USB
one can synchronize clocks of the micro and PC with microsecond
accuracy, I plan to try this but do not know how this will work.
On a sunny day (Sun, 17 Nov 2024 14:50:58 -0000 (UTC)) it happened antispam@fricas.org (Waldek Hebisch) wrote in <vhcvsg$28q26$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 17 Nov 2024 01:34:45 -0000 (UTC)) it happened
antispam@fricas.org (Waldek Hebisch) wrote in
<vhbh7j$26abk$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
Anyways how much processing power do I really need?
I program a lot of stuff in asm for Microchip PICs:
https://panteltje.nl/panteltje/pic/index.html
Nice. I have avoided PICs, using now mostly STM32 and coding in C.
One can create quite small and efficient programs in C. I use
assembler when I feel it is better but currently that is mainly
for delay loop. Doing all in efficient assembler would be large
effort for moderate gain (maybe 20% efficiency/size improvement),
and IME "easy assembler" tend to be less efficient than C.
In case of small micros like PICs you are so close to the hardware that you will need
to know how the various registers and stuff work anyways, no space / too much risc to allow for a compiler to change things.
Then C or some other high level language makes little sense.
After programming a few PICs you have build up an asm library and things become simple, repeats.
I use somebody else's integer math library.
Have not needed floats yet.. not even here in Fourier transform:
https://panteltje.nl/panteltje/pic/scope_pic/
And I opensource everything.
On Sun, 17 Nov 2024 09:33:54 -0800, john larkin <JL@gct.com> wrote:
On Sun, 17 Nov 2024 14:50:58 -0000 (UTC), antispam@fricas.org (Waldek >>Hebisch) wrote:
USB can do milliseconds, ethernet hundreds of microseconds, small
micros can do much better. Theoretically with a micro connected via USB >>>one can synchronize clocks of the micro and PC with microsecond
accuracy, I plan to try this but do not know how this will work.
We're designing some products around the RP2040, the Pi Pico
processor.
Turns out that in some cases, it's easier to bit-bang an SPI interface
than program an SPI engine. To fine-tune timings in 7 ns increments,
we can use no-op instructions.
I wonder what's a safe c-language NOP single-clock operation that no >>compiler is smart enough to optimize out and doesn't add a bunch of
loads and stores.
We're experimenting with that sort of timing on an oscilloscope. The
GCC or whatever code timing tools don't work in this case.
Something like
gpio_put(FIRST_GPIO, 1);
gpio_put(FIRST_GPIO, 0);
gpio_put(FIRST_GPIO, 1);
gpio_put(FIRST_GPIO, 0);
Makes the port pin change every 7 ns. That's astounding. So maybe a
dummy port bang is my no-op. Just repeat what we just set it to.
Code in assembly. It's trivial to use assembly code with c in gcc.
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 17 Nov 2024 14:50:58 -0000 (UTC)) it happened
antispam@fricas.org (Waldek Hebisch) wrote in
<vhcvsg$28q26$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
On a sunny day (Sun, 17 Nov 2024 01:34:45 -0000 (UTC)) it happened
antispam@fricas.org (Waldek Hebisch) wrote in
<vhbh7j$26abk$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
Anyways how much processing power do I really need?
I program a lot of stuff in asm for Microchip PICs:
https://panteltje.nl/panteltje/pic/index.html
Nice. I have avoided PICs, using now mostly STM32 and coding in C.
One can create quite small and efficient programs in C. I use
assembler when I feel it is better but currently that is mainly
for delay loop. Doing all in efficient assembler would be large
effort for moderate gain (maybe 20% efficiency/size improvement),
and IME "easy assembler" tend to be less efficient than C.
In case of small micros like PICs you are so close to the hardware that you will need
to know how the various registers and stuff work anyways, no space / too much risc to allow for a compiler to change things.
Then C or some other high level language makes little sense.
After programming a few PICs you have build up an asm library and things become simple, repeats.
Well, I heard that PICs are hard to program in C. I am not sure how
small you mean. Smallest micros I have are MSP430 with 256 bytes of
RAM and 8kB flash (but AFAICS C would work fine also on smaller ones,
say 64 bytes of RAM and 1kB flash). Cheapest one is STM8 with 1kB RAM
and 8kB flash. Smallest STM32 I have has 4kB RAM and 16kB flash, that
is plenty for many programs (actually I run most test programs entiriely
in RAM, so 4kB code+data). Of course one needs to work with hardware >registers and understand hardware. Below is my UART receive routine
(called from an interrupt handler) Actual data reception is very easy,
first line gets the data from UART. Rest of routine deals with receive >buffer (cyclic one):
void
do_usart1_rx(void)
{
uint8_t c = USART1_DR;
uint8_t head = i_buff.head;
uint8_t cnt = (head - i_buff.tail)&BUFF_SIZE_MASK;
/* Drop characters in case of buffer overflow */
if (cnt != BUFF_SIZE_MASK) {
i_buff.buff[head] = c;
head++;
head &= BUFF_SIZE_MASK;
i_buff.head = head;
}
}
Compiler generated assembly for STM32F103 (Cortex M3) is below:
.global do_usart1_rx
.thumb
.thumb_func
.type do_usart1_rx, %function
do_usart1_rx:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
ldr r3, .L7
ldr r0, [r3]
ldr r3, .L7+4
uxtb r0, r0
ldrb r2, [r3] @ zero_extendqisi2
ldrb r1, [r3, #1] @ zero_extendqisi2
uxtb r2, r2
subs r1, r2, r1
and r1, r1, #15
cmp r1, #15
beq .L1
adds r1, r3, r2
adds r2, r2, #1
and r2, r2, #15
strb r0, [r1, #2]
strb r2, [r3]
.L1:
bx lr
.L8:
.align 2
.L7:
.word 1073821700
.word .LANCHOR0
.size do_usart1_rx, .-do_usart1_rx
That is 17 executable instructions, 48 bytes of code and AFAICS only
two zero-extend instructions could be dropped. So one could save
2 instructions, but the rest is very much forced by how the processor
works (and by cyclic buffer logic). Compiled code for Cortex M0
is slightly different. The same C routine should work on STM8
(UART port address is different but data register should behave
the same as on STM32) and GD32VF103 (Riscv core but peripherials
compatible with STM32F103). Cyclic buffer logic could be copied
and used on different processors, like MSP430 or AVR.
Test program for UART routines is 1192 bytes code and uses probably
about 100 bytes of RAM (36 for global data, the rest is stack (I
made a conservative guess for possible stack use)). That is about
1.8% of available code space and 0.5% of available RAM. Of the code
336 bytes is table of interrupt vectors (essentially its presence is
forced by the hardware). The program includes setting clock to desired >frequency, configuration of pins, UART and interrupt controller.
BTW, the interrupt handler itself is:
void
usart1_isr(void)
{
uint32_t isr = USART1_SR;
if (isr&USART_SR_RXNE) {
do_usart1_rx();
}
if (isr&USART_SR_TXE) {
do_usart1_tx();
}
}
which generates 32 bytes of code.
I use somebody else's integer math library.
Cortex M have hardware 32-bit mutiplication and C compiler will
expand inline most of 64-bit operations. MSP430 and STM8 needs
support routines.
Have not needed floats yet.. not even here in Fourier transform:
https://panteltje.nl/panteltje/pic/scope_pic/
And I opensource everything.
Yes it all depends, I still have my old 8052 BASIC computer:
https://panteltje.nl/pub/8052AH_BASIC_computer/8052AH_BASIC_computer_inside2_img_1757.jpg
wrote an assembler for it so I could do inline assembler in the BASIC.
I used 5 pole audio connectors to make teh i2c bus external, with sensors and stuff connected to it all around the house.
from before year 2000.
As to PIC serial code
As you can see from the below example, PIC asm is very simple and straight forward.
That is the code in my GPS based radiation meter / logger with OLED display and SDcard storage:
https://panteltje.nl/panteltje/pic/gm_pic2/
Still working 24/7 after all these years... can hear it ticking on rasiation, logs to a Raspberry Pi 4 4 GB via a serial to USB adaptor.
ASM code:
https://panteltje.nl/panteltje/pic/gm_pic2/gm_pic2-0.8.asm
I like to comment in the code, but it is basically very simple.
Jan Panteltje <alien@comet.invalid> wrote:
Yes it all depends, I still have my old 8052 BASIC computer:
https://panteltje.nl/pub/8052AH_BASIC_computer/8052AH_BASIC_computer_inside2_img_1757.jpg
wrote an assembler for it so I could do inline assembler in the BASIC.
I used 5 pole audio connectors to make teh i2c bus external, with sensors and stuff connected to it all around the house.
from before year 2000.
Around 1985 I planned to build a Z80 machine, but then I got ZX Spectrum
and there was no need to build it.
As to PIC serial code
As you can see from the below example, PIC asm is very simple and straight forward.
That is the code in my GPS based radiation meter / logger with OLED display and SDcard storage:
https://panteltje.nl/panteltje/pic/gm_pic2/
Still working 24/7 after all these years... can hear it ticking on rasiation, logs to a Raspberry Pi 4 4 GB via a serial to
USB adaptor.
ASM code:
https://panteltje.nl/panteltje/pic/gm_pic2/gm_pic2-0.8.asm
I like to comment in the code, but it is basically very simple.
Well, I used to think "assembler requires comparable effort to C and
is more efficient", but then I looked how much time both take
and compared efficiency: assembler may be more efficient but
efficient assember requires significantly more effort than C.
One can write assembler in a way that saves effort, but then
it tends to be less efficient than output of a good C compiler,
and still takes a bit more effort than C. You may be used
to assembler, but if you are used to both, then reading C is
easier than reading assembler.
Anyway, I see no reason to use PIC-s, from normal sources
I would have to pay more for them than I pay for STM32 and
I see no special advantage of PICs.
BTW: It seems that there are few thousends of instructions in
your code, AFAICS object code for such a program when compiled
for something like STM32 would be of comparable size and C source
would be smaller.
On a sunny day (Mon, 18 Nov 2024 10:38:06 -0000 (UTC)) it happened antispam@fricas.org (Waldek Hebisch) wrote in <vhf5ec$2h6bb$1@paganini.bofh.team>:
Jan Panteltje <alien@comet.invalid> wrote:
Yes it all depends, I still have my old 8052 BASIC computer:
https://panteltje.nl/pub/8052AH_BASIC_computer/8052AH_BASIC_computer_inside2_img_1757.jpg
wrote an assembler for it so I could do inline assembler in the BASIC.
I used 5 pole audio connectors to make teh i2c bus external, with sensors and stuff connected to it all around the house.
from before year 2000.
Around 1985 I planned to build a Z80 machine, but then I got ZX Spectrum >>and there was no need to build it.
As to PIC serial code
As you can see from the below example, PIC asm is very simple and straight forward.
That is the code in my GPS based radiation meter / logger with OLED display and SDcard storage:
https://panteltje.nl/panteltje/pic/gm_pic2/
Still working 24/7 after all these years... can hear it ticking on rasiation, logs to a Raspberry Pi 4 4 GB via a serial to
USB adaptor.
ASM code:
https://panteltje.nl/panteltje/pic/gm_pic2/gm_pic2-0.8.asm
I like to comment in the code, but it is basically very simple.
Well, I used to think "assembler requires comparable effort to C and
is more efficient", but then I looked how much time both take
and compared efficiency: assembler may be more efficient but
efficient assember requires significantly more effort than C.
One can write assembler in a way that saves effort, but then
it tends to be less efficient than output of a good C compiler,
and still takes a bit more effort than C. You may be used
to assembler, but if you are used to both, then reading C is
easier than reading assembler.
Anyway, I see no reason to use PIC-s, from normal sources
I would have to pay more for them than I pay for STM32 and
I see no special advantage of PICs.
BTW: It seems that there are few thousends of instructions in
your code, AFAICS object code for such a program when compiled
for something like STM32 would be of comparable size and C source
would be smaller.
Yep, but most of that is in every 18F14K22 PIC code I wrote or from that
so all that just an afternoon or 2 to make it work.
I am not against C, but so close to the hardware as in the example I gave it makes little sense.
I use C all the time:
https://panteltje.nl/panteltje/newsflex/download.html
this Newsrreader I am using to read and reply here is written in C:
https://panteltje.nl/panteltje/newsflex/index.html
that uses linked lists,
I have a database of Usenet postings that goes back to my first Linux use in 1998 or so...
wrote that newsreader as there was no Free Agent for Linux...
Also in C is all the raspi code I wrote, no asm there at all,
but I use many libraries that may contain asm...
https://panteltje.nl/panteltje/newsflex/download.html
No C plush plush here... No Python either..
The problem with using someone else's libraries is that those often change, change maintainer and then lose functionalities or do not work at all anymore.
On Sun, 17 Nov 2024 14:50:58 -0000 (UTC), antispam@fricas.org (Waldek Hebisch) wrote:
USB can do milliseconds, ethernet hundreds of microseconds, small
micros can do much better. Theoretically with a micro connected via USB >>one can synchronize clocks of the micro and PC with microsecond
accuracy, I plan to try this but do not know how this will work.
We're designing some products around the RP2040, the Pi Pico
processor.
Turns out that in some cases, it's easier to bit-bang an SPI interface
than program an SPI engine. To fine-tune timings in 7 ns increments,
we can use no-op instructions.
I wonder what's a safe c-language NOP single-clock operation that no
compiler is smart enough to optimize out and doesn't add a bunch of
loads and stores.
We're experimenting with that sort of timing on an oscilloscope. The
GCC or whatever code timing tools don't work in this case.
Something like
gpio_put(FIRST_GPIO, 1);
gpio_put(FIRST_GPIO, 0);
gpio_put(FIRST_GPIO, 1);
gpio_put(FIRST_GPIO, 0);
Makes the port pin change every 7 ns. That's astounding. So maybe a
dummy port bang is my no-op. Just repeat what we just set it to.
"Jan Panteltje" <alien@comet.invalid> wrote in message news:vgq37s$oo9h$1@solani.org...
On a sunny day (Sun, 10 Nov 2024 09:51:49 -0000 (UTC)) it happened Cursitor >> Doom <cd999666@notformail.com> wrote in <vgpvnk$ao84$1@dont-email.me>:
On Sat, 9 Nov 2024 21:40:06 +0000, Liz Tuddenham wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
There's not a single person on this group today who can really add any >>>>> value here.
You do them a dis-service, there are some people here who can think with >>>> an open mind. Even if the ideas they come up with wouldn't work, trying >>>> to find out or explain why they wouldn't work is a good exercise and may >>>> lead to a better solution than just asking hams what they have done
before.
OK, that's entirely your call. But I think you'll find the number of >>>people here with expertise in VHF receiver design is zero and the >>>proportion of those with an adequate familiarity with designing for toobz >>>is a vanishingly small subset of that figure. :)
I designed plenty of VHF rx stuff, teefee works in that range,
including UHF.
But to go back in time and do it with toobs? No, I used transistors.
Only case I could think of for using toobs is when all semi-conductors
were destroyed by radiation.
But not much would be on air to listen for in that case.
And in that case shortwave would be a better place to listen for remaining lifeforms.
And grounded grid does not make a lot of sense, has not many advantages for a VHF input stage.
Why?
https://www.google.com/search?&q=valve+fm+tuner&udm=2
I can see at least two grounded grids and I don't recall a transistor FM tuner without a grounded base first stage.
Reduced sensitivity was ofted caused by a need to replace that transistor because being the first stage it gets what the antenna
gets.
john larkin <JL@gct.com> wrote:
On Sun, 17 Nov 2024 14:50:58 -0000 (UTC), antispam@fricas.org (Waldek
Hebisch) wrote:
USB can do milliseconds, ethernet hundreds of microseconds, small
micros can do much better. Theoretically with a micro connected via USB >>>one can synchronize clocks of the micro and PC with microsecond
accuracy, I plan to try this but do not know how this will work.
We're designing some products around the RP2040, the Pi Pico
processor.
Turns out that in some cases, it's easier to bit-bang an SPI interface
than program an SPI engine. To fine-tune timings in 7 ns increments,
we can use no-op instructions.
I wonder what's a safe c-language NOP single-clock operation that no
compiler is smart enough to optimize out and doesn't add a bunch of
loads and stores.
As JM wrote, with gcc (and I think clang too) you can use imline asm
like:
__asm__ volatile ("nop");
gcc is supposed to keep it. There is potential trouble with reordering,
in general gcc can move statements to a different place when it thinks
that the affect is the same. 'volatile' is supposed to prevent such
movement (gcc still may move "normal" code around it, but access to
GPIO should be volatile too and gcc will not reorder volatile
operations).
We're experimenting with that sort of timing on an oscilloscope. The
GCC or whatever code timing tools don't work in this case.
Oscilloscope is good to see what happens at the pins. For observing
internal time one can read systick register (I did not check RP2040,
but I think it can be configured to change every clock).
Something like
gpio_put(FIRST_GPIO, 1);
gpio_put(FIRST_GPIO, 0);
gpio_put(FIRST_GPIO, 1);
gpio_put(FIRST_GPIO, 0);
Makes the port pin change every 7 ns. That's astounding. So maybe a
dummy port bang is my no-op. Just repeat what we just set it to.
I you want accuracy up to a single clock, then your code is brittle.
RP2040 is a complex device and can do many things simultaneously.
There is large potential for undesired interference. Basically,
if you have code in a single bank of the RAM and your RP2040 is
doing nothing else than bit-banging, then you are resonably safe.
However, if SPI peripherial can do what you need, then IMO it
is better solution, as SPI is dedicated hardware block which can
operate without interference in parallel with other blocks.
I have no experience with radio design, but for curiosity looked at
several early TV sets from soviet block. _All_ tube circuits that
I found were common cathode in first stage, in late sixties apparently
they converged on caskode configuration (two early designs had
two common cathode stages). I found also few early transistor
circunts, majority was common base, one was common emiter. I
think reasonable guess is that tube characteristics make caskode
preferable, while for transitors (at least those from sixties and
seventies) common base seem to be better.
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