On 30/12/2021 19:04, Scott wrote:
> I think I am getting it now. Why did the London companies uniquely
> have to be routed via BT Tower? Was this because they provided the
> sustaining service to all of ITV?
There was nothing unique about it, both the BBC and ITV companies were
interconnected and connected to their transmitters by BT.
What was unique about London (after 1968 and until 1993) was that two
different companies had the ITV franchise on a time share basis.
Actually, between 1983 and 1993 it was three, because TV-am held the 6am
to 9:25am franchise slot.

> Why could they not have linked the LWT studio to the Thames studio and
> the Thames studio to the BT Tower. This could have dispensed with BT
> staff altogether and Thames could transfer control to LWT with staff
> at both ends.
>
> Or am I misunderstanding this completely?

They could have, but why order LWT to be routed via Thames, (that would
be like Sainsburys asking Tesco to handle their stock distribution ?)
It would have made Thames responsible for the technical integrity of
LWT's output. For the same reason, TV-am was not routed via the
'daytime' ITV companies
>> Your local ITV company had a engineer comparing the phase of the
>> incoming network signal, with his own local sync pulses, and modify the
>> phase of the local pulses to ensure a clean cut. He was doing that just
>> before the start of each programme, and just before each ad break. So at
>> least every 20 mins or so. The phase would drift over that period, even
>> though each company in the network had 'precision' SPGs
> I take it they couldn't give the job to Granada instead because this
> would involve leasing 200 miles of telephone lines for the data..

I don't understand what you're saying ?

On 30/12/2021 07:08 pm, Scott wrote:

> Chris Green <cl@isbd.net> wrote:
>> Scott <newsgroups@gefion.myzen.co.uk> wrote:
>
>>> You mean they were allowed to pre-record South Bank Show before 7 pm
>>> on a Friday :-)
>
>> Is that somehow different from recording it before 7pm?
>
> Note the smiley but what I meant was that Thames had the London
> franchise until 7 pm Friday and LWT from then on. If the show were
> recorded before 7 pm, LWT would not be a franchise holder.

Why not?

You don't think "Upstairs Downstairs" or "The Professionals" went out
live, do you?

On 30/12/2021 08:04 pm, Scott wrote:

> On Thu, 30 Dec 2021 19:24:07 +0000, Chris Green <cl@isbd.net> wrote:
>> Scott <newsgroups@gefion.myzen.co.uk> wrote:
>>> On Thu, 30 Dec 2021 18:52:17 +0000, Chris Green <cl@isbd.net> wrote:
>>>> Scott <newsgroups@gefion.myzen.co.uk> wrote:
>>>>>
>>>>> You mean they were allowed to pre-record South Bank Show before 7 pm
>>>>> on a Friday :-)
>
>>>> Is that somehow different from recording it before 7pm?
>
>>> Note the smiley but what I meant was that Thames had the London
>>> franchise until 7 pm Friday and LWT from then on. If the show were
>>> recorded before 7 pm, LWT would not be a franchise holder.
>
>> I was wondering how "pre-record" differs from "record", that's all. :-)
>
> I probably wanted to emphasise I meant recording the programme before
> transmission (when LWT did not hold the franchise) rather than during
> transmission (when it did). I think my attempt at humour has fallen
> flat.

I think you're right!

On Thu, 30 Dec 2021 20:38:50 +0000, JNugent <jennings&co@fastmail.fm>
wrote:

>On 30/12/2021 07:08 pm, Scott wrote:
>
>> Chris Green <cl@isbd.net> wrote:
>>> Scott <newsgroups@gefion.myzen.co.uk> wrote:
>>
>>>> You mean they were allowed to pre-record South Bank Show before 7 pm
>>>> on a Friday :-)
>>
>>> Is that somehow different from recording it before 7pm?
>>
>> Note the smiley but what I meant was that Thames had the London
>> franchise until 7 pm Friday and LWT from then on. If the show were
>> recorded before 7 pm, LWT would not be a franchise holder.
>
>Why not?
>
>You don't think "Upstairs Downstairs" or "The Professionals" went out
>live, do you?
I think I have conceded this attempt at humour has fallen flat. The
smiley was supposed to be a clue :-)

Mark Carver" <mark.carver@invalid.invalid> wrote in message
news:j368mhFcjo0U1@mid.individual.net...
> You're completely overthinking the problem. All you need to ensure is that
> the remote source is in phase with your own local SPG at the point you
> switch to them. The distance the remote signal has travelled is totally
> irrelevant.

I agree that the distance that the remote signal has travelled is
irrelevant, but you still need to *make* the remote signal, by the time it
reaches the switching centre, in phase with your local SPG. You can do that
either by letting the remote end generate its own sync and then delaying the
received signal until it matches your local sync; or you can send your own
sync, and compensate for the round-trip delay so the received signal will be
in phase. Either approach is as good as the other, though a single
broadcaster-wide sync source seems a slightly more elegant solution.

On Thu, 30 Dec 2021 20:12:07 +0000, Mark Carver
<mark.carver@invalid.invalid> wrote:

>On 30/12/2021 19:04, Scott wrote:
>> I think I am getting it now. Why did the London companies uniquely
>> have to be routed via BT Tower? Was this because they provided the
>> sustaining service to all of ITV?
>There was nothing unique about it, both the BBC and ITV companies were
>interconnected and connected to their transmitters by BT.
>What was unique about London (after 1968 and until 1993) was that two
>different companies had the ITV franchise on a time share basis.
>Actually, between 1983 and 1993 it was three, because TV-am held the 6am
>to 9:25am franchise slot.
>
>> Why could they not have linked the LWT studio to the Thames studio and
>> the Thames studio to the BT Tower. This could have dispensed with BT
>> staff altogether and Thames could transfer control to LWT with staff
>> at both ends.
>>
>> Or am I misunderstanding this completely?
>
>They could have, but why order LWT to be routed via Thames, (that would
>be like Sainsburys asking Tesco to handle their stock distribution ?)
>It would have made Thames responsible for the technical integrity of
>LWT's output. For the same reason, TV-am was not routed via the
>'daytime' ITV companies
>>> Your local ITV company had a engineer comparing the phase of the
>>> incoming network signal, with his own local sync pulses, and modify the
>>> phase of the local pulses to ensure a clean cut. He was doing that just
>>> before the start of each programme, and just before each ad break. So at
>>> least every 20 mins or so. The phase would drift over that period, even
>>> though each company in the network had 'precision' SPGs
>> I take it they couldn't give the job to Granada instead because this
>> would involve leasing 200 miles of telephone lines for the data..
>
>I don't understand what you're saying ?

I just meant could both outputs (Thames and LWT) have been
consolidated by Granada (as a seven day station) to feed into BT. I
think your previous explanation answers this (technical integrity). I
thought it might be a cost thing with the phone lines.

In article <sql7oh$fc9$1@dont-email.me>, NY <me@privacy.invalid> wrote:
> Mark Carver" <mark.carver@invalid.invalid> wrote in message
> news:j368mhFcjo0U1@mid.individual.net...
> > You're completely overthinking the problem. All you need to ensure is
> > that the remote source is in phase with your own local SPG at the
> > point you switch to them. The distance the remote signal has travelled
> > is totally irrelevant.

> I agree that the distance that the remote signal has travelled is
> irrelevant, but you still need to *make* the remote signal, by the time
> it reaches the switching centre, in phase with your local SPG. You can
> do that either by letting the remote end generate its own sync and then
> delaying the received signal until it matches your local sync; or you
> can send your own sync, and compensate for the round-trip delay so the
> received signal will be in phase. Either approach is as good as the
> other, though a single broadcaster-wide sync source seems a slightly
> more elegant solution.

The actual method used was to send control signals to the remote source so
that it's output reached the mixing point in sync; That included subcarrier.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 30/12/2021 21:18, NY wrote:
> Mark Carver" <mark.carver@invalid.invalid> wrote in message
> news:j368mhFcjo0U1@mid.individual.net...
>> You're completely overthinking the problem. All you need to ensure is
>> that the remote source is in phase with your own local SPG at the
>> point you switch to them. The distance the remote signal has
>> travelled is totally irrelevant.
>
> I agree that the distance that the remote signal has travelled is
> irrelevant, but you still need to *make* the remote signal, by the
> time it reaches the switching centre, in phase with your local SPG.
> You can do that either by letting the remote end generate its own sync
> and then delaying the received signal until it matches your local
> sync; or you can send your own sync, and compensate for the round-trip
> delay so the received signal will be in phase. Either approach is as
> good as the other, though a single broadcaster-wide sync source seems
> a slightly more elegant solution.
 You don't delay anything, instead you briefly advance or retard either
your own SPG, _or_ the remote SPG until both are in phase (as seen at
the geographical location of the switch)

This was the essence of both the ITV and BBC methods

"Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j36bkgFd5teU1@mid.individual.net...
>
>
> Your local ITV company had a engineer comparing the phase of the
> incoming network signal, with his own local sync pulses, and modify the
> phase of the local pulses to ensure a clean cut. He was doing that just
> before the start of each programme, and just before each ad break. So at
> least every 20 mins or so. The phase would drift over that period, even
> though each company in the network had 'precision' SPGs

You said in another post that live camera shots of the continuity
announcer, or captions (the shots also derived from live cameras I
presume) were shown at the start of incoming network programmes,
while the phase of the local SPG was being adjusted so it was in
sync.

In the case of adverts, presumably they'd have been switching
directly from a programme, to taped adverts, then back to the
programme again, with no locally generated live camera
feed in between, so how were things brought into sync in
this situation?

On 03/01/2022 00:59, Alexander wrote:
> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j36bkgFd5teU1@mid.individual.net...
>>
>> Your local ITV company had a engineer comparing the phase of the
>> incoming network signal, with his own local sync pulses, and modify the
>> phase of the local pulses to ensure a clean cut. He was doing that just
>> before the start of each programme, and just before each ad break. So at
>> least every 20 mins or so. The phase would drift over that period, even
>> though each company in the network had 'precision' SPGs
> You said in another post that live camera shots of the continuity
> announcer, or captions (the shots also derived from live cameras I
> presume) were shown at the start of incoming network programmes,
> while the phase of the local SPG was being adjusted so it was in
> sync.
>
> In the case of adverts, presumably they'd have been switching
> directly from a programme, to taped adverts, then back to the
> programme again, with no locally generated live camera
> feed in between, so how were things brought into sync in
> this situation?
>
They will have re-phased themselves just before the ad break, so while
they were still putting 'network' to air, that will have ensured a clean
switch back to the 'local' ads.
The amount of drift during the three minute ad break will have been
minimal, so the switch back to network will have only have had a tiny
glitch.

As you point out, they couldn't have resync'd during the actual ad break.

On Mon, 3 Jan 2022 13:25:03 +0000, Mark Carver
<mark.carver@invalid.invalid> wrote:

>On 03/01/2022 00:59, Alexander wrote:
>> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j36bkgFd5teU1@mid.individual.net...
>>>
>>> Your local ITV company had a engineer comparing the phase of the
>>> incoming network signal, with his own local sync pulses, and modify the
>>> phase of the local pulses to ensure a clean cut. He was doing that just
>>> before the start of each programme, and just before each ad break. So at
>>> least every 20 mins or so. The phase would drift over that period, even
>>> though each company in the network had 'precision' SPGs
>> You said in another post that live camera shots of the continuity
>> announcer, or captions (the shots also derived from live cameras I
>> presume) were shown at the start of incoming network programmes,
>> while the phase of the local SPG was being adjusted so it was in
>> sync.
>>
>> In the case of adverts, presumably they'd have been switching
>> directly from a programme, to taped adverts, then back to the
>> programme again, with no locally generated live camera
>> feed in between, so how were things brought into sync in
>> this situation?
>>
>They will have re-phased themselves just before the ad break, so while
>they were still putting 'network' to air, that will have ensured a clean
>switch back to the 'local' ads.
>The amount of drift during the three minute ad break will have been
>minimal, so the switch back to network will have only have had a tiny
>glitch.
>
>As you point out, they couldn't have resync'd during the actual ad break.
>
Were national adverts ever inserted at network level, eg during
football or network news, or always by the local contractor?

On 03/01/2022 06:07 pm, Scott wrote:
> On Mon, 3 Jan 2022 13:25:03 +0000, Mark Carver
> <mark.carver@invalid.invalid> wrote:
>
>> On 03/01/2022 00:59, Alexander wrote:
>>> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j36bkgFd5teU1@mid.individual.net...
>>>>
>>>> Your local ITV company had a engineer comparing the phase of the
>>>> incoming network signal, with his own local sync pulses, and modify the
>>>> phase of the local pulses to ensure a clean cut. He was doing that just
>>>> before the start of each programme, and just before each ad break. So at
>>>> least every 20 mins or so. The phase would drift over that period, even
>>>> though each company in the network had 'precision' SPGs
>>> You said in another post that live camera shots of the continuity
>>> announcer, or captions (the shots also derived from live cameras I
>>> presume) were shown at the start of incoming network programmes,
>>> while the phase of the local SPG was being adjusted so it was in
>>> sync.
>>>
>>> In the case of adverts, presumably they'd have been switching
>>> directly from a programme, to taped adverts, then back to the
>>> programme again, with no locally generated live camera
>>> feed in between, so how were things brought into sync in
>>> this situation?
>>>
>> They will have re-phased themselves just before the ad break, so while
>> they were still putting 'network' to air, that will have ensured a clean
>> switch back to the 'local' ads.
>> The amount of drift during the three minute ad break will have been
>> minimal, so the switch back to network will have only have had a tiny
>> glitch.
>>
>> As you point out, they couldn't have resync'd during the actual ad break.
>>
> Were national adverts ever inserted at network level, eg during
> football or network news, or always by the local contractor?

Did TV-AM (the only truly national ITV broadcaster) operate its own
advert sales and playout?

On 03/01/2022 18:09, JNugent wrote:
> Were national adverts ever inserted at network level, eg during
>> football or network news, or always by the local contractor?
No, always by the local contractors.
Even when it was the same ad in all regions at the same time. Remember
the three minute long 'Made by Robots' Fiat ad that appeared in the
middle of News at Ten ?
>
> Did TV-AM (the only truly national ITV broadcaster) operate its own
> advert sales and playout?

Yes, though two playout centres. One at Camden Lock (at the studios) an
other at Knutsford in Cheshire for the northern etc and Scottish
transmitters

On Mon, 3 Jan 2022 18:09:43 +0000, JNugent <jennings&co@fastmail.fm>
wrote:

>On 03/01/2022 06:07 pm, Scott wrote:
>> On Mon, 3 Jan 2022 13:25:03 +0000, Mark Carver
>> <mark.carver@invalid.invalid> wrote:
>>
>>> On 03/01/2022 00:59, Alexander wrote:
>>>> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j36bkgFd5teU1@mid.individual.net...
>>>>>
>>>>> Your local ITV company had a engineer comparing the phase of the
>>>>> incoming network signal, with his own local sync pulses, and modify the
>>>>> phase of the local pulses to ensure a clean cut. He was doing that just
>>>>> before the start of each programme, and just before each ad break. So at
>>>>> least every 20 mins or so. The phase would drift over that period, even
>>>>> though each company in the network had 'precision' SPGs
>>>> You said in another post that live camera shots of the continuity
>>>> announcer, or captions (the shots also derived from live cameras I
>>>> presume) were shown at the start of incoming network programmes,
>>>> while the phase of the local SPG was being adjusted so it was in
>>>> sync.
>>>>
>>>> In the case of adverts, presumably they'd have been switching
>>>> directly from a programme, to taped adverts, then back to the
>>>> programme again, with no locally generated live camera
>>>> feed in between, so how were things brought into sync in
>>>> this situation?
>>>>
>>> They will have re-phased themselves just before the ad break, so while
>>> they were still putting 'network' to air, that will have ensured a clean
>>> switch back to the 'local' ads.
>>> The amount of drift during the three minute ad break will have been
>>> minimal, so the switch back to network will have only have had a tiny
>>> glitch.
>>>
>>> As you point out, they couldn't have resync'd during the actual ad break.
>>>
>> Were national adverts ever inserted at network level, eg during
>> football or network news, or always by the local contractor?
>
>Did TV-AM (the only truly national ITV broadcaster) operate its own
>advert sales and playout?

Did the ITV companies handle adverts for Channel 4 when it started?

On Mon, 3 Jan 2022 18:29:09 +0000, Mark Carver
<mark.carver@invalid.invalid> wrote:

>On 03/01/2022 18:09, JNugent wrote:
>> Were national adverts ever inserted at network level, eg during
>>> football or network news, or always by the local contractor?
>No, always by the local contractors.
>Even when it was the same ad in all regions at the same time. Remember
>the three minute long 'Made by Robots' Fiat ad that appeared in the
>middle of News at Ten ?

I remember when Triang used to do and advert of 20 minutes or so in
the run-up to Christmas.
>>
>> Did TV-AM (the only truly national ITV broadcaster) operate its own
>> advert sales and playout?
>
>Yes, though two playout centres. One at Camden Lock (at the studios) an
>other at Knutsford in Cheshire for the northern etc and Scottish
>transmitters

Did they regionalise the adverts, and did it follow ITV regions?

On 03/01/2022 18:44, Scott wrote:
> On Mon, 3 Jan 2022 18:09:43 +0000, JNugent <jennings&co@fastmail.fm>
> wrote:
>
>> On 03/01/2022 06:07 pm, Scott wrote:
>>> On Mon, 3 Jan 2022 13:25:03 +0000, Mark Carver
>>> <mark.carver@invalid.invalid> wrote:
>>>
>>>> On 03/01/2022 00:59, Alexander wrote:
>>>>> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j36bkgFd5teU1@mid.individual.net...
>>>>>> Your local ITV company had a engineer comparing the phase of the
>>>>>> incoming network signal, with his own local sync pulses, and modify the
>>>>>> phase of the local pulses to ensure a clean cut. He was doing that just
>>>>>> before the start of each programme, and just before each ad break. So at
>>>>>> least every 20 mins or so. The phase would drift over that period, even
>>>>>> though each company in the network had 'precision' SPGs
>>>>> You said in another post that live camera shots of the continuity
>>>>> announcer, or captions (the shots also derived from live cameras I
>>>>> presume) were shown at the start of incoming network programmes,
>>>>> while the phase of the local SPG was being adjusted so it was in
>>>>> sync.
>>>>>
>>>>> In the case of adverts, presumably they'd have been switching
>>>>> directly from a programme, to taped adverts, then back to the
>>>>> programme again, with no locally generated live camera
>>>>> feed in between, so how were things brought into sync in
>>>>> this situation?
>>>>>
>>>> They will have re-phased themselves just before the ad break, so while
>>>> they were still putting 'network' to air, that will have ensured a clean
>>>> switch back to the 'local' ads.
>>>> The amount of drift during the three minute ad break will have been
>>>> minimal, so the switch back to network will have only have had a tiny
>>>> glitch.
>>>>
>>>> As you point out, they couldn't have resync'd during the actual ad break.
>>>>
>>> Were national adverts ever inserted at network level, eg during
>>> football or network news, or always by the local contractor?
>> Did TV-AM (the only truly national ITV broadcaster) operate its own
>> advert sales and playout?
> Did the ITV companies handle adverts for Channel 4 when it started?
Yes. For C4's first 10 years the ITV companies had to finance it
completely , but in return they sold and transmitted the ads in their
own regions.
So C4 was routed through each regional company to allow this. (Also
there was a glitch at 5:15pm every Friday on C4 in London as the routing
also changed from Thames to LWT)

On 03/01/2022 18:47, Scott wrote:Yes, though two playout centres. One at
Camden Lock (at the studios) an
>> other at Knutsford in Cheshire for the northern etc and Scottish
>> transmitters
> Did they regionalise the adverts, and did it follow ITV regions?

Yes, but no. Bigger regions.

By the way, forgot to say, Channel TV took its national ads from their
off-air mainland feed. Westward, then TSW, then TVS, then Meridian.
The mainland company sold the national ad space for them

"Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j3gbpgFa9diU1@mid.individual.net...
> On 03/01/2022 00:59, Alexander wrote:
>
>> You said in another post that live camera shots of the continuity
>> announcer, or captions (the shots also derived from live cameras I
>> presume) were shown at the start of incoming network programmes,
>> while the phase of the local SPG was being adjusted so it was in
>> sync.
>>
>> In the case of adverts, presumably they'd have been switching
>> directly from a programme, to taped adverts, then back to the
>> programme again, with no locally generated live camera
>> feed in between, so how were things brought into sync in
>> this situation?
>>
> They will have re-phased themselves just before the ad break, so while
> they were still putting 'network' to air, that will have ensured a clean
> switch back to the 'local' ads.
> The amount of drift during the three minute ad break will have been
> minimal, so the switch back to network will have only have had a tiny
> glitch.
>
> As you point out, they couldn't have resync'd during the actual ad break.

I guess my question was, how would they have synchronised the local
video tape playback (for ads) with a remote incoming programme feed?

On 03/01/2022 21:54, Alexander wrote:
> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j3gbpgFa9diU1@mid.individual.net...
>> On 03/01/2022 00:59, Alexander wrote:
>>
>>> You said in another post that live camera shots of the continuity
>>> announcer, or captions (the shots also derived from live cameras I
>>> presume) were shown at the start of incoming network programmes,
>>> while the phase of the local SPG was being adjusted so it was in
>>> sync.
>>>
>>> In the case of adverts, presumably they'd have been switching
>>> directly from a programme, to taped adverts, then back to the
>>> programme again, with no locally generated live camera
>>> feed in between, so how were things brought into sync in
>>> this situation?
>>>
>> They will have re-phased themselves just before the ad break, so while
>> they were still putting 'network' to air, that will have ensured a clean
>> switch back to the 'local' ads.
>> The amount of drift during the three minute ad break will have been
>> minimal, so the switch back to network will have only have had a tiny
>> glitch.
>>
>> As you point out, they couldn't have resync'd during the actual ad break.
> I guess my question was, how would they have synchronised the local
> video tape playback (for ads) with a remote incoming programme feed?
>
The local VTR, telecines, vision mixer, cameras etc were all locked to
the local Master SPG, and it was this that was 'drifted' to be in phase
with the incoming network.
That's why the M-SPG couldn't be drifted while the VTRs or telecines
were on air, because their servos would have become unstable.

In article <sqvra2$b5q$1@dont-email.me>, Alexander <none@nowhere.fr> wrote:

> "Mark Carver" <mark.carver@invalid.invalid> wrote in message
> news:j3gbpgFa9diU1@mid.individual.net...
> > On 03/01/2022 00:59, Alexander wrote:
> >
> >> You said in another post that live camera shots of the continuity
> >> announcer, or captions (the shots also derived from live cameras I
> >> presume) were shown at the start of incoming network programmes, while
> >> the phase of the local SPG was being adjusted so it was in sync.
> >>
> >> In the case of adverts, presumably they'd have been switching directly
> >> from a programme, to taped adverts, then back to the programme again,
> >> with no locally generated live camera feed in between, so how were
> >> things brought into sync in this situation?
> >>
> > They will have re-phased themselves just before the ad break, so while
> > they were still putting 'network' to air, that will have ensured a
> > clean switch back to the 'local' ads. The amount of drift during the
> > three minute ad break will have been minimal, so the switch back to
> > network will have only have had a tiny glitch.
> >
> > As you point out, they couldn't have resync'd during the actual ad
> > break.

> I guess my question was, how would they have synchronised the local
> video tape playback (for ads) with a remote incoming programme feed?

The VCR will have been running synchronised to local syncs. Before the ads
start that local SPG will have been synced to the incoming feed.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

Alexander <none@nowhere.fr> wrote:
>
> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j3gbpgFa9diU1@mid.individual.net...
>
> > On 03/01/2022 00:59, Alexander wrote:
> >
> >> You said in another post that live camera shots of the continuity
> >> announcer, or captions (the shots also derived from live cameras I
> >> presume) were shown at the start of incoming network programmes,
> >> while the phase of the local SPG was being adjusted so it was in
> >> sync.
> >>
> >> In the case of adverts, presumably they'd have been switching
> >> directly from a programme, to taped adverts, then back to the
> >> programme again, with no locally generated live camera
> >> feed in between, so how were things brought into sync in
> >> this situation?
> >>
> > They will have re-phased themselves just before the ad break, so while
> > they were still putting 'network' to air, that will have ensured a clean
> > switch back to the 'local' ads.
> > The amount of drift during the three minute ad break will have been
> > minimal, so the switch back to network will have only have had a tiny
> > glitch.
> >
> > As you point out, they couldn't have resync'd during the actual ad break.
>
> I guess my question was, how would they have synchronised the local
> video tape playback (for ads) with a remote incoming programme feed?
>
I've been sitting watching this thread go by and wondering *why* do
programs going out on different transmitters need to be synchronised
at all? It's not like the old 'synchronised chains' of MW radio
transmitters where one would quite likely be able to get a signal from
more than one transmitter. A TV aerial is designed to point at one
particular transmitter with the specific intent of minimising signals
from anywhere else. If you're using an indoor 'omnidirectional'
aerial then, presumably, you have a huge signal from a local
transmitter and nothing else will interfere.

Simple manual 'starting the program at the right time' would keep
things within a second or so, surely near enough.

--
Chris Green
·

On 04/01/2022 10:31, Chris Green wrote:
> Alexander <none@nowhere.fr> wrote:
>> "Mark Carver" <mark.carver@invalid.invalid> wrote in message news:j3gbpgFa9diU1@mid.individual.net...
>>
>>> On 03/01/2022 00:59, Alexander wrote:
>>>
>>>> You said in another post that live camera shots of the continuity
>>>> announcer, or captions (the shots also derived from live cameras I
>>>> presume) were shown at the start of incoming network programmes,
>>>> while the phase of the local SPG was being adjusted so it was in
>>>> sync.
>>>>
>>>> In the case of adverts, presumably they'd have been switching
>>>> directly from a programme, to taped adverts, then back to the
>>>> programme again, with no locally generated live camera
>>>> feed in between, so how were things brought into sync in
>>>> this situation?
>>>>
>>> They will have re-phased themselves just before the ad break, so while
>>> they were still putting 'network' to air, that will have ensured a clean
>>> switch back to the 'local' ads.
>>> The amount of drift during the three minute ad break will have been
>>> minimal, so the switch back to network will have only have had a tiny
>>> glitch.
>>>
>>> As you point out, they couldn't have resync'd during the actual ad break.
>> I guess my question was, how would they have synchronised the local
>> video tape playback (for ads) with a remote incoming programme feed?
>>
> I've been sitting watching this thread go by and wondering *why* do
> programs going out on different transmitters need to be synchronised
> at all?

We're not talking about the signals from the transmitters being
synchronised. We're talking about each video source within the output of
a TV channel (or within a TV programme) being synchronised. In other
words, imagine switching between two cameras where one is on 'Line 1' at
the same time the other is on 'Line 250'. As you cut between them, your
TV will exhibit a 'frame roll' as it re-locks to that camera's sync
pulses. If you were to try and fade between the two, you'd just get one
image half way up the other, (at the very least).

Therefore in all TV broadcasting environments, all of the equipment that
is a video source, (VTR, Cameras, Telecine, Caption Generators) must all
be 'in step'. That's achieved using a master sync pulse generator
(M-SPG), that acts as the station's heartbeat.

That's all good, but it becomes complicated when you need to receive,
and cut to a feed from another TV station (regardless whether it's next
door, or in New Zealand)

On 04/01/2022 10:59, Mark Carver wrote:
> We're not talking about the signals from the transmitters being
> synchronised.

Though in the days of analogue TV, transmitters had offsets which were
supposed to reduce the effect of interference from other transmitters on
the same frequency so it was important to keep reasonable stability.

In some cases they had to have the transmitter locked to GPS to ensure
precise frequency stability. We had one like that and had the cost of
new transmitters, GPS receivers, our labour etc paid by a foreign
broadcaster.

On 04/01/2022 11:07, MB wrote:On 04/01/2022 10:59, Mark Carver wrote:
>> We're not talking about the signals from the transmitters being
>> synchronised.
>
> Though in the days of analogue TV, transmitters had offsets which were
> supposed to reduce the effect of interference from other transmitters
> on the same frequency so it was important to keep reasonable stability.

Yep, either +5/3rds, 0, or -5/3rds line frequency. Different kettle of
fish, but it reduced CCI to a fine pattern of 'Venitan Blinds' .You were
basically pushing the energy from the interfering signal's video carrier
(which was in multiples of the line rate 15.625kHz) into spectral gaps
within the wanted signal.

There was a really neat demonstration of it on one of the IBA
Engineering Trade progs.

> In some cases they had to have the transmitter locked to GPS to ensure
> precise frequency stability.  We had one like that and had the cost of
> new transmitters, GPS receivers, our labour etc paid by a foreign
> broadcaster.

Yep.  Here's an example

http://downloads.bbc.co.uk/rd/pubs/reports/1993-04.pdf

In article <sr19q2$ac7$1@dont-email.me>,
MB <MB@nospam.net> wrote:
> On 04/01/2022 10:59, Mark Carver wrote:
> > We're not talking about the signals from the transmitters being
> > synchronised.

> Though in the days of analogue TV, transmitters had offsets which were
> supposed to reduce the effect of interference from other transmitters on
> the same frequency so it was important to keep reasonable stability.

> In some cases they had to have the transmitter locked to GPS to ensure
> precise frequency stability. We had one like that and had the cost of
> new transmitters, GPS receivers, our labour etc paid by a foreign
> broadcaster.

RTE, ISTR

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle