Do transmitters have some mechanism that automatically click in a
replacement module, or complete replacement transmitter (the power
stage, at least), in the event of failure?
I'm watching (well, it's on) FreeView 231 (BBC News); I'm at TN27 0DD,
and I think get my signals from a transmitter beginning with H (I'm
pretty sure _not_ Blue Bell hill). The sound suddenly cut out - at about 17:37:40 - and I looked up, and picture was off too, "no signal" being displayed. It hadn't gradually deteriorated - stuttering audio, freezing video, as I'd expect if it was an interference fade - it just cut off suddenly.
Within about 10 or 15 seconds, it was back - certainly before 17:38:05,
when I looked back at my clock.
I think I've often seen this.
Do transmitters have some sort of mechanism that does a replacement - or complete replacement transmitters on permanent standby?
Of course, the fault _could_ be at my end, but I can't think of a
mechanism which would cause the symptoms as I describe - perfect, then nothing, then comes back perfect. I'd have expected degradation, and not
the sudden return. I'm pretty sure it isn't a vehicle passing through
the path.
_Could_ be a dropout of signal _to_ the transmitter, but I'd have
thought it would have popped up an error message - test card or
something - if that had happened.
Only high power main stations have standby transmitters nowadays.
Dover and Bluebell Hill both radiate 20KW so are unlikely to have
standby kit, but Heathfield, being a 80KW site may or may not, I would suspect the latter.
_Could_ be a dropout of signal _to_ the transmitter, but I'd have
thought it would have popped up an error message - test card or
something - if that had happened.
On Tue 02/11/2021 17:54, J. P. Gilliver (John) wrote:[]
Do transmitters have some mechanism that automatically click in a >>replacement module, or complete replacement transmitter (the power
stage, at least), in the event of failure?
I'm watching (well, it's on) FreeView 231 (BBC News); I'm at TN27
0DD, and I think get my signals from a transmitter beginning with H
[]Do transmitters have some sort of mechanism that does a replacement
- or complete replacement transmitters on permanent standby?
Assuming you are at or near Charing you could be getting Bluebell Hill
which is close to and on the south side of the M2 about 14m NW of you,
or West Hougham which is above the old Dover Road about 21m ESE of you.
Both require your aerial to be horizontal. Following the H theory you
could be getting Heathfield which is about 8m WNW.
To tell them apart, if you can receive Forces TV on channel 96 you are >receiving Bluebell Hill, if not you are receiving Dover or Heathfield.
Only high power main stations have standby transmitters nowadays. Dover
and Bluebell Hill both radiate 20KW so are unlikely to have standby
kit, but Heathfield, being a 80KW site may or may not, I would suspect
the latter.
On 02/11/2021 17:54, J. P. Gilliver (John) wrote:
_Could_ be a dropout of signal _to_ the transmitter, but I'd have
thought it would have popped up an error message - test card or
something - if that had happened.
No, the transmitters are all dumb terminals, they have the complete
DVB-T transport stream delivered directly to them for centralised
coding/mux sites.
It is impossible for them to generate and insert a caption locally,
because that's at the 'video' rather than 'mux' level.
In article <3S0Nzf99RaghFw47@255soft.uk>, J. P. Gilliver (John) <G6JPG@255soft.uk> scribeth thus
On Tue, 2 Nov 2021 at 18:21:22, Woody <harrogate3@ntlworld.com> wrote
(my responses usually follow points raised):
On Tue 02/11/2021 17:54, J. P. Gilliver (John) wrote:[]
Do transmitters have some mechanism that automatically click in a
replacement module, or complete replacement transmitter (the power
stage, at least), in the event of failure?
I'm watching (well, it's on) FreeView 231 (BBC News); I'm at TN27
0DD, and I think get my signals from a transmitter beginning with H
[]Do transmitters have some sort of mechanism that does a replacement
- or complete replacement transmitters on permanent standby?
Assuming you are at or near Charing you could be getting Bluebell Hill
which is close to and on the south side of the M2 about 14m NW of you,
or West Hougham which is above the old Dover Road about 21m ESE of you.
Both require your aerial to be horizontal. Following the H theory you
could be getting Heathfield which is about 8m WNW.
Ah, Heathfield, that's the one; I can never remember the name. (I keep
thinking of Hanningfield, where I used to live, but know it isn't that.)
Here yer go some nice rigging pics!...
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=943
Not really..To tell them apart, if you can receive Forces TV on channel 96 you are
receiving Bluebell Hill, if not you are receiving Dover or Heathfield.
"Invalid channel".
Only high power main stations have standby transmitters nowadays. Dover
and Bluebell Hill both radiate 20KW so are unlikely to have standby
kit, but Heathfield, being a 80KW site may or may not, I would suspect
the latter.
Presumably not manned, so automatic; whatever the mechanism, I'm
impressed that an 80 kW transmitter can just be switched in in a matter
of seconds.
Does it have to be run in some sort of hot standby mode, so there isn't
thermal shock or many similar such when it's brought on line?
How _much_ redundancy of this sort is there - one? Two?: once it _has_
switched in the backup, presumably it has to call someone to come to
replace something. (I can see that more than one doesn't need to be on
"hot standby", if any do.)
Yes in effect, thats what happens..
On 02/11/2021 18:21, Woody wrote:
Only high power main stations have standby transmitters nowadays.
Dover and Bluebell Hill both radiate 20KW so are unlikely to have
standby kit, but Heathfield, being a 80KW site may or may not, I would
suspect the latter.
Dover is 80 kW ERP, Bluebell Hill and Heathfield are both 20kW sites.
I think all 'main' stations (of which those three are) all have
main/standby kit. They certainly all have diverse power and fibre feeds.
On Tue, 2 Nov 2021 at 18:21:22, Woody <harrogate3@ntlworld.com> wrote
(my responses usually follow points raised):
On Tue 02/11/2021 17:54, J. P. Gilliver (John) wrote:[]
Do transmitters have some mechanism that automatically click in a >>>replacement module, or complete replacement transmitter (the power
stage, at least), in the event of failure?
I'm watching (well, it's on) FreeView 231 (BBC News); I'm at TN27
0DD, and I think get my signals from a transmitter beginning with H
[]Do transmitters have some sort of mechanism that does a replacement
- or complete replacement transmitters on permanent standby?
Assuming you are at or near Charing you could be getting Bluebell Hill >>which is close to and on the south side of the M2 about 14m NW of you,
or West Hougham which is above the old Dover Road about 21m ESE of you. >>Both require your aerial to be horizontal. Following the H theory you
could be getting Heathfield which is about 8m WNW.
Ah, Heathfield, that's the one; I can never remember the name. (I keep >thinking of Hanningfield, where I used to live, but know it isn't that.)
To tell them apart, if you can receive Forces TV on channel 96 you are >>receiving Bluebell Hill, if not you are receiving Dover or Heathfield.
"Invalid channel".
Only high power main stations have standby transmitters nowadays. Dover
and Bluebell Hill both radiate 20KW so are unlikely to have standby
kit, but Heathfield, being a 80KW site may or may not, I would suspect
the latter.
Presumably not manned, so automatic; whatever the mechanism, I'm
impressed that an 80 kW transmitter can just be switched in in a matter
of seconds.
Does it have to be run in some sort of hot standby mode, so there isn't >thermal shock or many similar such when it's brought on line?
How _much_ redundancy of this sort is there - one? Two?: once it _has_ >switched in the backup, presumably it has to call someone to come to
replace something. (I can see that more than one doesn't need to be on
"hot standby", if any do.)
In article <3S0Nzf99RaghFw47@255soft.uk>, J. P. Gilliver (John) ><G6JPG@255soft.uk> scribeth thus[]
Ah, Heathfield, that's the one; I can never remember the name. (I keep >>thinking of Hanningfield, where I used to live, but know it isn't that.)
Here yer go some nice rigging pics!...
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=943
Does it have to be run in some sort of hot standby mode, so there isn't >>thermal shock or many similar such when it's brought on line?Not really..
How _much_ redundancy of this sort is there - one? Two?: once it _has_ >>switched in the backup, presumably it has to call someone to come to >>replace something. (I can see that more than one doesn't need to be on
"hot standby", if any do.)
Yes in effect, thats what happens..
On Tue, 2 Nov 2021 at 23:22:47, tony sayer <tony@bancom.co.uk> wrote
(my responses usually follow points raised):
In article <3S0Nzf99RaghFw47@255soft.uk>, J. P. Gilliver (John)[]
<G6JPG@255soft.uk> scribeth thus
Ah, Heathfield, that's the one; I can never remember the name. (I keep
thinking of Hanningfield, where I used to live, but know it isn't
that.)
Here yer go some nice rigging pics!...
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=943
Thanks. I'd forgotten (or didn't know) that mb21 pages have a randomly-selected BBC clock, including the one with the bouncy
pointer! Ah, nostalgia ...
[]
Does it have to be run in some sort of hot standby mode, so there isn'tNot really..
thermal shock or many similar such when it's brought on line?
Impressive then, if an 80 kW transmitter can just be turned on like that.
On Tue, 2 Nov 2021 at 18:37:33, Mark CarverDuring the DSO and B700 set ups, they'd often do an overnight power test
<mark.carver@invalid.invalid> wrote (my responses usually follow
points raised):
On 02/11/2021 17:54, J. P. Gilliver (John) wrote:Interesting, thanks.
_Could_ be a dropout of signal _to_ the transmitter, but I'd have
thought it would have popped up an error message - test card or
something - if that had happened.
No, the transmitters are all dumb terminals, they have the complete
DVB-T transport stream delivered directly to them for centralised
coding/mux sites.
It is impossible for them to generate and insert a caption locally,
because that's at the 'video' rather than 'mux' level.
If the signal - the feed - _did_ drop out, would they transmit all
zeroes, or whatever the relevant equivalent is? I suspect my TV would
show "no signal" whether it was actually receiving no RF, or an
incorrect packet structure (or whatever the right term is).
The very high powered transmitters - such as Emley, Belmont, Sutton
Coldfield etc - are American made valve based units and have main and standby. There is a huge UPS to keep them running if mains fails whilst
the standby generator starts. Most of these output around 10KW and run
in hot standby pairs.
The next size down are either Rhode and Schwartz or NEC and run various powers depending on how many (solid state) PA modules are fitted IMSMC
up to about 4KW.
The low power relays use a single unit solid state transposer and come
in 20W or 50W versions.
Do transmitters have some mechanism that automatically click in a
replacement module, or complete replacement transmitter (the power stage,
at least), in the event of failure?
I'm watching (well, it's on) FreeView 231 (BBC News); I'm at TN27 0DD, and
I think get my signals from a transmitter beginning with H (I'm pretty
sure _not_ Blue Bell hill). The sound suddenly cut out - at about
17:37:40 - and I looked up, and picture was off too, "no signal" being displayed. It hadn't gradually deteriorated - stuttering audio, freezing video, as I'd expect if it was an interference fade - it just cut off suddenly.
Within about 10 or 15 seconds, it was back - certainly before 17:38:05,
when I looked back at my clock.
I think I've often seen this.
Do transmitters have some sort of mechanism that does a replacement - or complete replacement transmitters on permanent standby?
Of course, the fault _could_ be at my end, but I can't think of a
mechanism which would cause the symptoms as I describe - perfect, then nothing, then comes back perfect. I'd have expected degradation, and not
the sudden return. I'm pretty sure it isn't a vehicle passing through the path.
_Could_ be a dropout of signal _to_ the transmitter, but I'd have thought
it would have popped up an error message - test card or something - if
that had happened.
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf
"Usenet is a way of being annoyed by people you otherwise never would have met."
- John J. Kinyon
On 02/11/2021 18:21, Woody wrote:
Only high power main stations have standby transmitters nowadays. Dover
and Bluebell Hill both radiate 20KW so are unlikely to have standby kit,
but Heathfield, being a 80KW site may or may not, I would suspect the
latter.
Dover is 80 kW ERP, Bluebell Hill and Heathfield are both 20kW sites.
I think all 'main' stations (of which those three are) all have
main/standby kit. They certainly all have diverse power and fibre feeds.
On Tue, 2 Nov 2021 at 18:21:22, Woody <harrogate3@ntlworld.com> wrote (my responses usually follow points raised):
On Tue 02/11/2021 17:54, J. P. Gilliver (John) wrote:[]
Do transmitters have some mechanism that automatically click in a
replacement module, or complete replacement transmitter (the power
stage, at least), in the event of failure?
I'm watching (well, it's on) FreeView 231 (BBC News); I'm at TN27 0DD,
and I think get my signals from a transmitter beginning with H
[]Do transmitters have some sort of mechanism that does a replacement -
or complete replacement transmitters on permanent standby?
Assuming you are at or near Charing you could be getting Bluebell Hill >>which is close to and on the south side of the M2 about 14m NW of you, or >>West Hougham which is above the old Dover Road about 21m ESE of you. Both >>require your aerial to be horizontal. Following the H theory you could be >>getting Heathfield which is about 8m WNW.
Ah, Heathfield, that's the one; I can never remember the name. (I keep thinking of Hanningfield, where I used to live, but know it isn't that.)
To tell them apart, if you can receive Forces TV on channel 96 you are >>receiving Bluebell Hill, if not you are receiving Dover or Heathfield.
"Invalid channel".
Only high power main stations have standby transmitters nowadays. Dover
and Bluebell Hill both radiate 20KW so are unlikely to have standby kit, >>but Heathfield, being a 80KW site may or may not, I would suspect the >>latter.
Presumably not manned, so automatic; whatever the mechanism, I'm impressed that an 80 kW transmitter can just be switched in in a matter of seconds.
Does it have to be run in some sort of hot standby mode, so there isn't thermal shock or many similar such when it's brought on line?
How _much_ redundancy of this sort is there - one? Two?: once it _has_ switched in the backup, presumably it has to call someone to come to
replace something. (I can see that more than one doesn't need to be on
"hot standby", if any do.)
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf
"Purgamentum init, exit purgamentum." Translation: "Garbage in, garbage
out."
To tell what was going on, you would have needed to check the other streams >on that transmitter, but most of the time I think its a distribution issue, >not a busted transmitter.
In the old days they used to have back ups, but I have no idea what they do
in the days of digital. I'd imagine the actual duty cycle of output modules >was a lot more on digital, since there is far more data on the carrier.
Brian
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