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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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22nd Sep 2020, 2:46 am | #1 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
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Non–TC/Teletext Trade Test Transmissions?
Hi!
This query refers to the non T.C./Teletext Trade Test Transmissions! I used to switch the TV on to BBC2 in the morning hours before programmes started, and usually before school hours, and amongst the patterns I saw:– a) Colour bars full–screen; b) Full white raster; c) V.I.T.S. full–screen; d) Smooth ramp, white on left and black on right; e) Half–white/half–black, split horizontally; f) I saw on one rare occasion, a single small white dot in the centre of the screen on a black background, this was not a switch–off spot as there was a continuous tone accompanying it – I only ever saw this once! g) Very coarse grid white crosshatch patterns, much coarser than customarily used for convergence; Can anyone tell me about these – purposes, times, etc? Have any other unusual patterns ever been seen besides these? Chris Williams
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25th Sep 2020, 1:26 am | #2 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
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Re: Non–TC/Teletext Trade Test Transmissions?
Full-screen VITS now there's an oxymoron!
Full-screen pulse & bar used to be seen occasionally. A very early memory for me from the days when our set only received the single BBC TV channel, was seeing a black cruciform pattern on a white background, which I would learn much later were called "Art Bars". Art for artificial, as it was electronically generated. If I can trust my memory from 60 years ago, I seem to recall there was always a tone on the accompanying sound when this patten was showing.
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25th Sep 2020, 1:44 am | #3 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
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Re: Non–TC/Teletext Trade Test Transmissions?
Now this would have been very cool to see at the time, and I was in the right area, but sadly our TV couldn't receive ITV at the beginning.
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25th Sep 2020, 7:18 am | #4 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,799
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Re: Non–TC/Teletext Trade Test Transmissions?
Worth keeping just for the G9 callsign. Bet that exceeded 150W DC to the final valve...
David
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25th Sep 2020, 6:00 pm | #5 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
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Re: Non–TC/Teletext Trade Test Transmissions?
G9+3 were research & development licences, I was going to say quite separate from amateur radio... but I'm not so sure.
Look! our own Andy Emmerson (midshires) G8PTH. had one. from https://youtu.be/BiXkHErNxC4?t=247
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25th Sep 2020, 8:13 pm | #6 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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Re: Non–TC/Teletext Trade Test Transmissions?
That mast and transmitter was used for trade aerial alignment prior to some (or all?) ITA transmitters going live. I believe it was also used when the Emley Moor mast collapsed.
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27th Sep 2020, 8:00 am | #7 | |
Pentode
Join Date: Sep 2019
Location: Perth, Western Australia, Australia.
Posts: 199
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Re: Non–TC/Teletext Trade Test Transmissions?
Quote:
The only Brit test signal I remember seeing was a sweep, in 1971 on "the Beeb", when I was in England for a while. Meanwhile, back in Oz, at the ABW2 site, the Standard test signals we used in the early days were FF sawtooth from a Marconi generator, 50Hz squarewave & "bump tests" from that same genny, a video sweep signal from a Marconi "sideband analyser"(SBA), Pulse & Bar from a different generator, & occasionally either video sweep or sawtooth from a Fernseh PGM 75. When we went to colour, we used a Tek148, which produced standard VITs either in their normal format, or as FF signals , FF sawtooth, 50Hz squarewave, as well as "bump" signals. We used a newer Marconi SBA for sweeping the Tx. Our old Marconi transmitters were "high level modulated", so the sideband analyser was most appropriate. The "IF modulated" transmitters at other sites were usually tested with RF sweepers, instead, although when I went to the Private Sector, they still preferred the SBA, even with such Tx. We did a full set of video & audio tests on both transmitter combined each Saturday morning, as the station didn't open till 12 noon. Once a month, we did individual tests on each transmitter separately. The PGM75 could produce other signals than the ones we used. Before my time, they used line rate & higher rectangular pulses, but as they produced harmonics beyond the video passband, they had limited utility. |
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27th Sep 2020, 12:30 pm | #8 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
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Re: Non–TC/Teletext Trade Test Transmissions?
There was a tape of various moving and still scenes, some with graphical overlays, I think the footage was mute. It was used to evaluate the effect on real-world receivers of increasing the number of Teletext lines.
The same footage was used some years later when the sound carrier level was reduced, and NICAM data was was applied to the vision.
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30th Sep 2020, 1:37 pm | #9 |
Nonode
Join Date: May 2006
Location: St Albans, Herts, UK.
Posts: 2,193
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Re: Non–TC/Teletext Trade Test Transmissions?
When I was young (ages ago!) there used to be an order to the the test transmissions before test card F appeared at 9am. I think the order was half white/half black for 10 minutes, grey scale for 10 minutes, then the pulse and bar (full screen) for a further 10 minutes.
We were had the choice of three regions and Wenvoe sometimes did something different and had the smooth ramp grey scale you mention. I think this happened when BBC2 Wales had a different start up time to the network. Again, all this is from hazy memories form 40 or more years ago. Does anyone remember also that the back to front greyscale (black on the left, white on the right) was occasionally transmitted without a sound carrier or vertical sync signal when the transmitter was first switched on? I assume this was transmitted directly from the transmitter.
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30th Sep 2020, 7:57 pm | #10 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
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Re: Non–TC/Teletext Trade Test Transmissions?
Hi!
I also remember the "Test Card Memory Lane" site, now apparently defunct, mentioned the 'full screen VITS" test had black vertical identification lines on the left–hand side white bar that indicated what transmitter/region was radiating the test, but unfortunately I can't find this info online any more – can anyone help with more about this? Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
30th Sep 2020, 8:25 pm | #11 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Non–TC/Teletext Trade Test Transmissions?
I remember a "Maltese Cross" type of test-card shown in the 'dark hours' - it was active in that it click-rotated about the centre-point over a minute, and the striations on the arms of the cross had microsecond-graduations so you could assess multipath reflections.
There was also a strange graticule-thing [imagine looking through several layers of chain-link-fencing, each adding its own colored fringe-refraction-patterns]. This was US 1960s NTSC. I spent some time in the DFW area with my parents, who regularly stayed up early/late to sync their phonecalls with the UK, and tuning-around-on-the-TV was kinda fun! |