[Synchrodyne]

Wireless World for October, 1961, in its National Radio Show Review, mentions both the Ekco (T398) and Pye (no model number given) dual-standard TV receivers that were on display there.

WW notes that both OEMs assumed that the TAC proposed 625-line standard (later System I) would become reality, as it had not at the time been ratified. Pye used a 38.9 MHz vision IF, the same as for the Gerber 625-line system, presumably because the UK industry had not yet done the homework wherein it landed on 39.5 MHz. (As an aside, I have a vague notion that 38.9v/32.9s MHz IFs were used in South Africa for System I receivers.) Also, I wonder if the Ekco and Pye receivers had 3-gang UHF tuners. I think the 4-gang type might have appeared after the UK 625-line standard was cast in stone and the desired receiver parameters (including 53 dB (?) image rejection) had been articulated. Cyldon’s first UHF tuner, the UT, was 3-gang and I should think was initially aimed at the export market.

The Pye dual-standard receiver was stated to have a 4.25 MHz video bandwidth, as determined by the IF bandpass curve, which seems a bit pessimistic. Roughly, that would have limited horizontal definition to about the same level as 2.75 MHz on 405-lines, which was probably reached by the better receivers. I should have thought that at least 5.0 MHz would have been a more reasonable target for the early 625-line receivers. Perhaps, though Pye has simply carried over established practice from its export 625-line Gerber system receivers.

Once dual-standard receivers became the norm, I suspect that some makers downgraded the 405-line sections as compared with pre-dual standard practice, for example abandoning black level agc. If so, this would be analogous to the downgrading of AM sections in radio receivers once FM-AM combinations became the norm.

Curiously, the same WW article moved on to describing the colour television display at the same show, and included comment to the effect that positive vision modulation was better for NTSC colour systems. But it seems that the editorial staff was not game enough to ask as to why, that being the case, the TAC had opted for negative modulation for its proposed 625-line system. In its November, 1961 issue, WW reported upon the French Radio Show, and noted the French decision to go with positive modulation for UHF 625-line TV broadcasts, but made no editorial comment about that choice.

Cheers,