From the Wireless and Electrical Trader, 27 August 1960. Page 577.
Pye Group Festival Hall Exihibition.
A switchable 405/625 21" TV receiver to operate on both the 405 line system in Bands 1 and 3 and on the 625 line system in Band 4.
The set had press button change-over from one to the other and covered 51 channels - 13 on 405 lines and 38 on 625 lines. Compared with a normal set there were two additional controls and two aerial sockets.
It certainly would be interesting to discover if this set employed a chassis which would become the V700D which was the first fully switchable 625/405 TV receiver to be sold in the UK.
Also on display the Pye TT1 and in full production the first British made full size transistorized portable TV receiver. Ready for sale late 1960.
Geordie McBoyne.
Interesting indeed.
I wonder if any other UK manufacturer had a set fully designed by then ready for production.
I recall reading somewhere that PYE jumped the gun with their early dual standard sets which used System G with 5.5MHz sound - this was, of course, before the specification for System I with 6MHz was formulated and approved for use in the UK.
I'm also sure that the article also said that, to successfully realign the IF strip for 6MHz sound required some of the dust iron cores to be replaced by brass ones!
Somebody later came across a supply of brand new and boxed PYE VHF export sets - with the printing on the back cover in English and Arabic! - and asked me if I could modify one for UK use.
We had a few new UHF tuners on the shelf, so I fitted one and realigned the sound with no problems (or changing of cores!).
So I got one and carried out the same modification.
I couldn't wait for 3-channel UHF transmissions to start but, unfortunately, a few months after it happened, the LOPT burnt up!
Didn't Pye also jump the gun with Band III capable sets? I think the VT2 came out in 1954, before the industry wide agreed date for launching "ITV" sets.
But weren't the frequency allocations for the eight UK Band 3 channels already decided upon by 1953?
"Also on display the Pye TT1 and in full production the first British made full size transistorized portable TV receiver. Ready for sale late 1960".
Actually when you think about it, by the end 1960 Pye weren't all that far behind America and Japan with the development of transistorised TV sets.
The TT1 has a full size CRT whereas a year earlier Philco introduced the Safari transistor TV which used a tiny 2" CRT.
Although it has to said in 1960 Motorola were advertising their 19" CRT portable TV set.
Geordie McBoyne.
(20-02-2018, 04:33 PM)Geordie McBoyne Wrote: [ -> ]But weren't the frequency allocations for the eight UK Band 3 channels already decided upon by 1953?
I think they were but I also seem to remember reading about an industry-wide agreement not to release Band III sets too early.
(20-02-2018, 04:33 PM)Geordie McBoyne Wrote: [ -> ]But weren't the frequency allocations for the eight UK Band 3 channels already decided upon by 1953?
Certainly, the ITU Stockholm 1952 Meeting (ST52) outcome included a full set of Band III allocations for the UK. However, these were provisional only, as noted in this excerpt from Wireless World 1952 October:
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attachment=17243]
I haven’t checked, but I should think that this list, from WW 1953 June, was taken from the ST52 Final Acts:
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attachment=17244]
Probably quite a few of the ST52 listings were provisional or later changed anyway. For example, there was an allocation for French TV channel F3, which was never in fact used. (My take on this is that channel F3 was probably abandoned to avoid the need for “double-ended” IF strips in TV receivers. With a vision-low IF strip, channels F2 and F4 were still usable, so that was the “lesser cost” pathway taken, although a longer-term consequence, almost certainly unforeseen at the time, was the eventual need for System L’ in Band I, with inverted channels.)
Cheers,
Steve
Wireless World 1961 October included a description of a Pye dual-standard receiver that may have been a stepping stone between the 1960 prototype at interest and the initial production model:
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attachment=17245]
The receiver described was intended for System I (initially known as the TAC system) in 625-line mode, but had a 38.9 MHz vision IF.
A close look at the vision IF passband suggests that it might have been derived from a previous System B model. The basic passband was of double-Nyquist form, with the -6 dB points at 34.65 (405 vision) and 38.9 MHz (625 vision). But the left-hand (34.65 MHz) flank looks a bit less steep than the right-hand (38.9 MHz) flank, which is really somewhat contrary. If anything, the 38.9 MHz flank should have been lesser-sloped. However, one may also imagine that if the 625 sound trap were moved from 32.9 MHz to 33.4 MHz, as would have been the case for System B, then the flanks would have been quite similar. So maybe Pye got from System B to System I simply by moving the 625 sound trap?
The double Nyquist IF was no doubt a low-cost way to build a dual standard IF, in that it could be used “as was” for 625, with a 38.15 MHz sound trap switched in for 405, certainly simpler than separate bandshaping filters for each standard. But there was definitely a penalty in terms of 625 vision bandwidth. 4.25 MHz (against the nominal 5.0 MHz) for System B was not very good, but 4.25 MHz (against the nominal 5.5 MHz) for System I surely fell into the grim category. Considering that Pye was a strong proponent of 625, one would have expected it to have designed prototype receivers that extracted the maximum from the system, including close to full vision bandwidth. (Not to mention the use of gated black level AGC, and black level retention/restoration.) One may hope that the production version got close to 5.5 MHz vision bandwidth.
Cheers,
Steve
(21-02-2018, 03:09 AM)Synchrodyne Wrote: [ -> ] But there was definitely a penalty in terms of 625 vision bandwidth. 4.25 MHz (against the nominal 5.0 MHz) for System B was not very good, but 4.25 MHz (against the nominal 5.5 MHz) for System I surely fell into the grim category. Considering that Pye was a strong proponent of 625, one would have expected it to have designed prototype receivers that extracted the maximum from the system, including close to full vision bandwidth. (Not to mention the use of gated black level AGC, and black level retention/restoration.) One may hope that the production version got close to 5.5 MHz vision bandwidth.
I wonder if this could be the System G set I referred to with it's sound IF moved to 6MHz for System I?
In which case wouldn't it have made more sense to move the vision IF to the UK standard's specified 39.5MHz? This would have improved the 625-line vision response to 4.85MHz. Again, not good but a lot better than 4.25MHz!
Even at 4.85mHz horizontal resolution would have been worse than on 405 lines.
Let's not forget 625line BBC2 take up was poor initially. Programing was for a select audience and complaints about poor picture quality were rife.
The broadcasters blamed the set makers and they inturn blamed the broadcasters.
It was odd though that those rubbish dual standard sets and those single standard sets released prior to duplication suddenly improved picture wise in November 1969!!