• Do (at least FreeView) transmitter have auto-repair or auto-backup?

    From J. P. Gilliver (John)@21:1/5 to All on Tue Nov 2 17:54:28 2021
    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

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  • From Woody@21:1/5 to All on Tue Nov 2 18:21:22 2021
    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 (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.

    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.

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  • From Mark Carver@21:1/5 to Woody on Tue Nov 2 18:34:02 2021
    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.

    --- SoupGate-Win32 v1.05
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  • From Mark Carver@21:1/5 to All on Tue Nov 2 18:37:33 2021
    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From J. P. Gilliver (John)@21:1/5 to Woody on Tue Nov 2 20:50:05 2021
    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."

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From J. P. Gilliver (John)@21:1/5 to mark.carver@invalid.invalid on Tue Nov 2 20:54:31 2021
    On Tue, 2 Nov 2021 at 18:37:33, Mark Carver
    <mark.carver@invalid.invalid> wrote (my responses usually follow points raised):
    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.

    Interesting, thanks.

    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).
    --
    J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

    "To YOU I'm an atheist; to God, I'm the Loyal Opposition." - Woody Allen

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  • From Woody@21:1/5 to tony sayer on Tue Nov 2 23:58:21 2021
    On Tue 02/11/2021 23:22, tony sayer wrote:
    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

    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?

    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..


    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From tony sayer@21:1/5 to All on Tue Nov 2 23:17:43 2021
    In article <iudekrF3lleU1@mid.individual.net>, Mark Carver <mark.carver@invalid.invalid> scribeth thus
    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.


    They will have a TX at least, they can't afford to be off-line for hours
    or maybe longer, it ain't on to have it off for long;!...

    --
    Tony Sayer


    Man is least himself when he talks in his own person.

    Give him a keyboard, and he will reveal himself.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From tony sayer@21:1/5 to All on Tue Nov 2 23:22:47 2021
    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

    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?

    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..
    --
    Tony Sayer


    Man is least himself when he talks in his own person.

    Give him a keyboard, and he will reveal himself.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From J. P. Gilliver (John)@21:1/5 to tony sayer on Wed Nov 3 01:27:37 2021
    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't >>thermal shock or many similar such when it's brought on line?

    Not really..

    Impressive then, if an 80 kW transmitter can just be turned on like
    that.

    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..

    Anyone know if a Heathfield transmitter _has_ clicked over to its
    standby this (well, Tuesday) evening?
    --
    J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

    If it's not on fire, it's a software problem.

    --- SoupGate-Win32 v1.05
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  • From Mark Carver@21:1/5 to All on Wed Nov 3 08:34:34 2021
    On 03/11/2021 01:27, J. P. Gilliver (John) wrote:
    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't
    thermal shock or many similar such when it's brought on line?

    Not really..

    Impressive then, if an 80 kW transmitter can just be turned on like that.

    It's 80kW ERP. Power up the feeders is typically around 10dB less than
    that, so 8kW ish

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Mark Carver@21:1/5 to All on Wed Nov 3 08:38:18 2021
    On 02/11/2021 20:54, J. P. Gilliver (John) wrote:
    On Tue, 2 Nov 2021 at 18:37:33, Mark Carver
    <mark.carver@invalid.invalid> wrote (my responses usually follow
    points raised):
    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.

    Interesting, thanks.

    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).
    During the DSO and B700 set ups, they'd often do an overnight power test
    a few days beforehand. To avoid any receivers latching on to the
    transmissions during overnight auto-scans, they'd transmit null packets.
    My telly would indicate a signal present tuning manually, but on an
    auto-store would simply ignore and sail past.

    --- SoupGate-Win32 v1.05
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  • From MB@21:1/5 to Woody on Wed Nov 3 09:07:42 2021
    On 02/11/2021 23:58, Woody wrote:
    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.


    I am not familiar with all this funny post-DSO stuff but there were a
    small number of the lower power ones with a changeover system in the
    analogue days.

    Also solid state transmitters tend to have multiple modules so failure
    of some will just result in a drop in output power (hopefully).

    In the first generation of UHF transmitters / transposers, quite a
    number had quite different types of transmitters as main and standby
    (including different manufacturers). Some were one offs as many
    manufacturers had a try and making UHF transmitters - don't forget this
    was the early days of solid state devices that would work at UHF!

    The ITA/IBA/whatever_they_called_themselves_that_week had different philosophies. The BBC tended to have transmitters that were self
    contained and would decide to change over themselves but ITA seemed to
    like to have remote control. BBC initially had remote resets so (if you
    were lucky) it would sort itself out.

    I was told of one ILR transmitter that had a home built unit that reset
    after a certain number of rings of the telephone!

    --- SoupGate-Win32 v1.05
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  • From Brian Gaff (Sofa)@21:1/5 to G6JPG@255soft.uk on Wed Nov 3 09:47:23 2021
    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

    --

    This newsgroup posting comes to you directly from...
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    Blind user, so no pictures please
    Note this Signature is meaningless.!
    "J. P. Gilliver (John)" <G6JPG@255soft.uk> wrote in message news:8OOPUB6UtXghFwph@255soft.uk...
    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

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  • From Brian Gaff (Sofa)@21:1/5 to Mark Carver on Wed Nov 3 09:51:37 2021
    What about Hannington. Back in the old analogue days we got good results
    here from there, even though Crystal Palace was line of sight. Back then
    the regional variations made it worthwhile having other regions, but now not
    so much.
    Brian

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    Blind user, so no pictures please
    Note this Signature is meaningless.!
    "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:iudekrF3lleU1@mid.individual.net...
    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.


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  • From Brian Gaff (Sofa)@21:1/5 to G6JPG@255soft.uk on Wed Nov 3 09:56:35 2021
    Depends on the technology used for the output stages and if you are speaking ERP or actual transmitter powers.
    I remember many of the low power original sites back in the analogue days
    did have a back up. I guess as they were low power, there was not a problem. However being very reliable has no doubt resulted in them saving a few
    pennies by not having a back up.
    Brian

    --

    This newsgroup posting comes to you directly from...
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    Note this Signature is meaningless.!
    "J. P. Gilliver (John)" <G6JPG@255soft.uk> wrote in message news:3S0Nzf99RaghFw47@255soft.uk...
    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."

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  • From J. P. Gilliver (John)@21:1/5 to briang1@blueyonder.co.uk on Wed Nov 3 18:46:10 2021
    On Wed, 3 Nov 2021 at 09:47:23, "Brian Gaff (Sofa)"
    <briang1@blueyonder.co.uk> wrote (my responses usually follow points
    raised):
    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.

    It was only out for 10-20 seconds - I wouldn't have had time. But I
    think you're right; I think I've seen it several times this year, so I
    hope it isn't the latter!

    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

    The waveform is _different_ - a lot more like white noise. (On analogue,
    a blank screen - white [on A] or black [on I] would give a pretty high
    duty cycle!)
    --
    J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

    By most scientific estimates sustained, useful fusion is ten years in
    the future - and will be ten years in the future for the next fifty
    years or more. - "Hamadryad", ~2016-4-4

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