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Forum Free Registration Closed
Granada Television Brochure, 1970s
Long Gone UK TV Shops
Memories of a Derwent Field Service Engineer
PYE Australia Circa 1971
Radios-TV VRAT
Fabulous Fablon
Thorn TX10 Chassis
Crusty-TV Museum, Analogue TV Network
Philips N1500 Warning!
Rumbelows
Thorn EMI Advertising
Thorn’s Guide to Servicing a VCR
Ferguson 3V24 De-Robed
Want to tell us a story?
Video Circuits V15 – Tripler Tester
Thorn Chassis Guide
Remove Teletext Lines & VCR Problems
Ceefax (Teletext)
Suggestions
Website Refresh
Colour TV Brochures
1970s Lounge Recreation
CrustyTV Vintage Television Museum
Linda Lovelace Experience
Humbars on a Sony KV2702
1972 Ultra 6713
D|E|R Service “The Best”
The one that got away
Technical information
The Line Output Stage
The map
Tales of a newly qualified young engineer.
Tales of a Radio Rentals Van Boy
Sanyo SMD
Disastrous Company Rebranding
1969 Philips G22K511
Memories Of The TV Trade
Crazy house
Dirty TV screens
Dual Standard and Single Standard CTV’s
Radios-TV on YouTube
The Winter of 62/63
A domestic audio installation
1979 Ferguson Videostar Deluxe 3V16
Music centre modifications
Unusual record player modification
B&K 467 Adapters
Mishaps In The Trade
1971 Beovision 3200
405 lines shutdown..
As part of this, when did the UHF TV coverage reach the point where it essentially duplicated the 405-line VHF TV coverage, such that elimination of the VHF network would not cause loss of coverage, even though it might require that some viewers acquire new receivers? There was an article, “The First Thousand Transmitters”, in Wireless World 1981 January that indicated that building of UHF relay stations was ongoing, so presumably there were still some gaps at that stage.
Also, when were the last 405-line relay stations commissioned? I have a notion that this might have been circa 1970. If so, they would have opened on the cusp of unavailability of new domestic equipment that was capable of receiving them. Presumably the rationale for the late relays was to provide better reception for some existing viewers with 405-line only receivers, at least in areas where the arrival of the 625-line service was some time off.
There was a dual standard Pye TVT11 broadcast monitor fed off a Thorn WJ12 television rack mount receiver (which I still have) in the Master Control Room (MCR) that monitored this service full time.
Would these have been old units, from the 1960s? Or was professional dual-standard equipment still made well into the 1970s? The Thorn WJ11/WJ12 at least appears to date from the mid-1960s or earlier, judging by the attached advertisement from Wireless World 1965 January. As no “solid- state” claims were made for it – as was the fashion in the early solid-state days - it looks as if might have been valved.
Cheers,
There was an article, “The First Thousand Transmitters”, in Wireless World 1981 January that indicated that building of UHF relay stations was ongoing, so presumably there were still some gaps at that stage.
I used to go on holiday to Watermouth Cove in North Devon from 1986 till 1993, up until about 1989/90 the only signal we could get was Welsh TV from Wenvoe across the Bristol channel. They built a relay TX at Berrynarbor about a mile or so away & we got perfect English South West TV pictures from there. So they were still building 625 TX's into the late 80's early 90's. Berrynarbor is a Freeview lite TX now with a power of 2 watts..
I suppose that was a case where, because of the incidence of local topography, the local rely was intended to provide the appropriate regional service rather than fill in a gap that hitherto had been without any service at all. My recollection of the North Devon coast (the last time I was there was 1995, I think) was that reception of inland transmitters to the south or so would not have been easy, whereas Wenvoe was just across the water.
Re the final extensions of the 405-line network, the attached item from Wireless World 1965 February outlines the BBC Stage 4 plan, which I suspect might have been the last.
Re late 405-line receiving equipment, I remembered that somewhere I had some information on the Marconi Marine (Mimco) Nomad multistandard shipboard TV receiver (actually a tuner delivering baseband audio and video), which covered System A, 405-lines amongst others. The manual I have is dated 1973 January, and is the 2nd edition. So the fact that the manual was reissued would lead one to assume that it was still in production at the time. The circuitry is not inspiring, though, particularly for an item that was in the industrial/professional class. It looks to have been an early silicon planar-based (BF167, BF173, etc.) UK dual-standard (A and I) circuit to which had been added switchable traps and three extra intercarrier sound channels to cover Systems B/G/H, D/K and M/N. The latter each used a TAA350 with slope detection, something that might be associated with the low end of the domestic receiver market. AGC for 405 was mean level, and for the other (negative vision modulation) systems, peak level without noise gating. (Maybe there was no significant VHF band impulsive interference aboard ships....)
Cheers,
Steve
The IBA transmitter pocket guide from 1976 March shows that of its 405-line VHF TV transmitters, three each were commissioned in 1969 and 1970 respectively, all others being earlier. So it would seem that 1970 marked the end of the 405-line transmitter build program.
Cheers,
Steve
Hi All, Thanks for the warm welcome. In the MCR control room all the monitors where professional units when I joined Thames Television based at Euston in 1982. The colour units where Philips Hybrid monitors which where being replaced with Barco CTVM2s. The B&W monitors where Pye TVT11s and where only just being updated before I left in 1989. These could be switched between 405 and 625 line. It was only the 405 line off-air monitor that was set to 405 line. The unit I have is the WJ12 horizontal rack mount unit. It is dual standard mostly valve so has a UHF and VHF tuner (both valve). It was only used for 405 line VHF. I never worked on it as I cannot remember it going wrong! The 625 line colour off air unit was a Decca solid state receiver which did require maintenance from me occasionally. Both these units where there when I joined Thames and I'm guessing that the 405 line receiver would have come from Television House when Thames took over from Associated Rediffusion in 1969?
Hi Hurty, I think that you mentioned in one of the lost postings that the Thorn WJ12 circuit was mostly valve-based, but with transistors used for the video and audio output and afc sections. I am curious about the agc section as well; was that done with transistors? Black level agc implies some kind of gating, and this would have to come from the sync, given that there was no LOPT. With valves that probably meant some video amplification to get to the level required for sync separation, whereas with transistors it could be done at reasonably low levels. One may visualize a valve-based black level agc system requiring several valves; video amplifier, sync separator, pulse generator, agc valve itself.
Cheers,
Steve
Great upload of the IBA Pocket Guide Steve, Newhaven was the last VHF transmitter to open, as late as August 1970. Remarkably the same VHF information remained as late as the October 1979 issue. They were still some areas dependent on the 405-line services at that time, I remember reading an article in the local newspaper about a UHF relay opening that year, prior to this the area was dependent on the VHF services, "Which is to be phased out soon".
Continuing on the IBA nostalgia theme, here's a colour map of 405-line coverage taken from the "1975 Guide To Independent Television" book.
Cheers,
Brian
Hi Steve, The VHF tuner is a type MT6 (PC97 and PCF805) with a valve UHF tuner and the valve i.f. is the Thorn 850 i.f. panel with the last 1" cut off and the video output valve not fitted (see photo). The video goes directly from the detector to the transistor amplifier board (see photo) where indeed the agc voltage is generated and taken back to the i.f. agc line. and this maintains the video output to the set 1 volt. There are a couple of EF85's on a separate board which takes a sniff if the final i.f. which I think is used for a.f.c. The last picture is the unit tuned to Channel 1, the output then taken to a Channel 4 modulator and displayed on my Ferguson Personal tuned to channel 4. Not bad results.
Nice results!
Thanks for the additional information. Re the afc, one may see the utility of an IF side-chain. With such the passband ahead of the afc discriminator could be “de-Nyquisted”, as it were, and centred over the vision carrier (39.5 MHz), without affecting the main vision IF channel. Also a limiter could be included. That kind of passband (essentially symmetrical about the vision carrier) would also be better for intercarrier generation, and it is conceivable that the intercarrier could be taken from the limiter grid.
Cheers,
Steve
Continuing on the IBA nostalgia theme, here's a colour map of 405-line coverage taken from the "1975 Guide To Independent Television" book.
That’s a nice map.
One may see that with 8 Band III channels at its disposal, the ITA/IBA had an easier time of it in terms of achieving near-national coverage than the BBC. The ITA had 47 Band III transmitters spread across the 8 channels. If one allows that there were two at St. Hilary, then the corrected total becomes 46 on a single-program basis.
On the other hand the BBC apparently had 111 VHF TV transmitters, 101 in Band I and 10 in Band III. The Band III transmitters at Wenvoe and Sandale carried second programs, so the single-program corrected total would be 109. One could also question the inclusion of Winter Hill, as that was installed not so much to extend coverage but to allow a regional split, and perhaps to obtain the benefits of co-siting with the corresponding ITA regional transmitter. So the corrected total could be 108, more than twice the IBA total.
As noted earlier in this thread, with the 5 Band I channels, the BBC was effectively “chasing its own tail”, this due to both the paucity of channels and the propensity for Band I frequencies to cause interference at significant distances. Thus, once down to gap-fill level, any given transmitter was likely constrained in its power output and polar diagram so as not to cause undue co-channel interference, which in turn would mean that it would not properly fill the gap in question, requiring further gap-filling on a smaller scale with a repetition of the same problems.
To be fair to the ITA, it had its own problems in that initially it had access to but a few Band III channels, so possibly its initial network planning departed from what could have been done had all 8 channels been available in 1955.
I suppose one could ask the question, what if the original planning had been for 2½ program national coverage using maximal co-siting of transmitters and assignment of channels on a best-fit basis without either program having a Band I or a Band III bias. By 2½ program I mean two program national coverage with provision for some additional regional transmitters, which was how the UK VHF TV network turned out anyway.
Cheers,
Steve
Very interesting thread. I sometimes wonder how things would have evolved had ITV been allowed to use band 1 in 1956 & BBC band 3 from same date? We could have had band 1 only areas like I believe New Zealand had, I'm thinking London ITV on channel 5 & North on channel 1. Of course we had Lincolnshire on band 3, oh I'm dreaming again, lol..
Yes, here in NZ the Waikato/Bay of Plenty had TV1 and TV2 both in Band I, channels NZ1 and NZ3 respectively, vertically polarized, from the Te Aroha transmitter. In our vicinity, most of the Band I aerials, usually 3-element are still in place. The original plan for 2 national programs in Bands I and III changed when TV3 came along and was shoehorned in. Co-siting was abandoned and we had a nearby Band III transmitter for TV3.
Regarding late 405-line receiving equipment, a 1969 receiver is described here: http://www.bbceng.info/ti/eqpt/UN1_585.pdf . It looks to be relatively simple when compared with this one: http://www.bbceng.info/ti/eqpt/TV_REC_3.pdf .
As noted earlier in this thread, with the 5 Band I channels, the BBC was effectively “chasing its own tail”, this due to both the paucity of channels and the propensity for Band I frequencies to cause interference at significant distances.
Actually, I made the earlier comment not in this thread, but in the “VHF System ‘A’ Transmitter Data..” thread. So we have some cross-modulation...
Cheers,
Steve
Actually, I made the earlier comment not in this thread, but in the “VHF System ‘A’ Transmitter Data..” thread. So we have some cross-modulation...
Which reminds me that in certain areas of the UK there were voids where UHF coverage didn't get through due to the terrain. Certain parts of the Amber valley Matlock area spring to mind. I don't think everyone was sold on the offerings of UHF but when the summers brought "continental interference" UHF was a good selling point if you could get it.
Eddie
I'm wondering if anyone in Lancashire, Lincolnshire or South Wales still watched the BBC on band 1 when it became available on band 3. They must have thought Christmas had come early in the summer with no sp-E interference. Even we on the outskirts of Nottingham (Bestwood Village) watched ch 13 from Belmont with a snowy picture when Sutton Coldfield was blasted out by sp-E...
I'm wondering if anyone in Lancashire, Lincolnshire or South Wales still watched the BBC on band 1 when it became available on band 3. They must have thought Christmas had come early in the summer with no sp-E interference. Even we on the outskirts of Nottingham (Bestwood Village) watched ch 13 from Belmont with a snowy picture when Sutton Coldfield was blasted out by sp-E...
The first of my two Sobells was tuned to Channels 2, 9 and 13. This TV was in the Granada region, so was tuned to Channels 2 (BBC1 Holme Moss) and Channel 9 (ITA Winter Hill), but was tuned for Channel 13 as well (BBC1 Winter Hil) for when that opened in 1968, shortly ahead of the changes to ITV which led to the launch of Yorkshire Television.
This TV was in the Granada region, so was tuned to Channels 2 (BBC1 Holme Moss) and Channel 9 (ITA Winter Hill), but was tuned for Channel 13 as well (BBC1 Winter Hil) for when that opened in 1968, shortly ahead of the changes to ITV which led to the launch of Yorkshire Television.
One small point: BBC1 was on channel 12.
viewtopic.php?f=5&t=7745#p81389
One small point: BBC1 was on channel 12.
I've just tested the set again after seeing your comment, indeed the TV is tuned to 12 and not 13 as I originally thought.
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