Re: Introduction PCC189 in Mullard tuners?
Hi Synchrodyne,
Yes, it has taken me a while to figure out the French 819-line set-up. Interestingly there isn't a web site explaining it this way, so I had to discover it myself. But I indeed had an "aha-Erlebnis", as the Germans say, when I saw the LO-frequencies coincide with the opposing channel vision or sound, depending upon the IF concept used. And when you draw the frequency figures it all becomes clear. An additional complication was that there are many "wrong" sources on the internet, mixing up channel numbers and frequencies. This is undoubtedly partly due to confusion caused by the French authorities when they abandoned the original 14MHz channel scheme and switched to the 13,15MHz bandwidth and tête-bêche scheme. In one of the early Philips tuner Service Manuals the frequencies were even wrong!
As to the effect on the drum tuners I haven't seen anything, as I would expect. By choosing the right coils the frequency-specific biscuits any filter or oscillator frequency could be selected. So assuming that a French tuner would step from channel F2 to F12 as most of them did, you would see on the biscuits a continuously reducing inductance for the input matching and bandpass filters, and an alternating large-small oscillator coil, linked to the oscillator switching for even and odd channels. As far as I can see there was no technical limitation whatsoever to realise this. (In this context it is interesting to see how this was managed in the non-drum type electronic transistor tuners of the end 60s to 70's, before there were digital memories. I'm almost there, finishing the last valve tuner story. Curious to see what the result will be.)
Cheers, Pieter
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