Resurrecting an oldie a PYE Cambridge

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Resurrecting an oldie a PYE Cambridge

Post by jomac on Sat Sep 28, 2013 6:38 pm

I recently acquired a very old PYE Cambridge in remarkably good condition which had a couple of crystals on the 4Mtr band. Now i hate wasting stuff and this old set (now 50 years old) wasnt worth recycling for the bits due to size etc. But something made me want to give the girl a new lease of life.

The set had been nicely converted from AM to NBFM and could be switched between both modes and a narrow filter fitted.

I would like to synthesize this set to cover the full 70.000 to 70.500 Mhz band. I have built a few of Harry's "Improved CMOS RF Synthesizer" and very happy with the results this gives, this is the synth i want to use, because i have even interfaced one with a PIC micro.

The question is, which is the best way to mix the output from the synth? If i go to far back into the multiplier chain, i probably wont get the right frequency steps after multiplication.

As i want to use parts im used to, what would be the best approach to mixing the output from the synth, to give a final 70 to 70.5 Mhz? The original CMOS synth has an output of 50Khz to 2Mhz (?) The two mixers ive used in the past have been the NE602/612 and the Minicircuits mixers.

Really the question area's are what frequencies are the best to mix at, and the best approach to this problem?

jomac

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Join date : 2013-08-26

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