30-07-2022, 01:49 PM
(29-07-2022, 10:27 PM)AdrianPH Wrote: I had been reading through some of the posts by Joe Sousa on the Radiomuseum site and it was the statement of: - 'Model r326, by Aleksandrov Radio Works in Russia, uses the 1ZH37B dual grid pentode in mixer service.' '[/i]
I am struggling a bit to understand this and wonder if this is the type of thing you mean: -
If not could you do a simple hand sketch some time.
I am considering a second mixer stage down to 455 at some point going from 10.7 to 455 for NBFM, in effect having two demodulators. I think I can see that it is easier at 10.7 to 455 because the centre tapped transformer could be tuned for a single frequency and not across 88 to 108 or what ever band I go for.
The R326 is using it at HF, not VHF *I think*, and I'm not sure that's it's the front end mixer. I'd have to check, in any case that's a pretty crazy set. Certainly most Russian VHF applications were below 70 MHz.
Certainly you can use a 1j37b as 10.7 MHz to 455 kHz for NBFM or HF dual conversion. However I'm not sure that the 1j24b doesn't work better (feed LO to g2 and RF or IF to g1) and certainly dramatically lower filament current.
The 1j37b doesn't need as much LO drive, but needs more complicated centre tapped transformer. It's certainly likely to work well as a detector or frequency doubler if driven with a differential signal on g1a and g1b, with DC bias to centre tap (often 0V via decoupled leak resistor of 2.2 M Ohms.)
Joe is the expert.
