Peter,
This very technique was used by Yaesu in several tube transceivers I've
found. It was shown in the book, "Understanding Radio" by the Untied
States Armed Forces Institute, published in 1940 and 1951 by McGraw
Hill. In the book, it mainly described using triodes in the circuit
where Yaesu mainly used dual tubes having a triode and a pentode (6U8)
as the receive mixer. The pentodes G1 was driven by the output of the
oscillator. There were some military receivers using similar circuitry
which I have the schematics here. This is the very information I am
looking for. Thanks for the input.
Will Matney
peter.chadwick@Zarlink.Com wrote:
Bill said:
>But if the local oscillator signal is strong enough to simply turn
on and off the mixer tube it does become a very effective >frequency
mixer. It then appears to be an analog mixer multiplying a signal
with a square wave.
It does reduce the conversion gain, though. That's the big problem
with switching mixers. The so called 'Gilbert cell' (which Barrie
Gilbert doesn't claim as his - it was first patented by a guy from
RCA as a 4 quadrant multiplier - Barrie's claim is that he was the
first to suggest using it as a mixer, and even that's disputed) can be
oeprated in lower gain as a switching mixer, and in higher gain as an
analogue multiplier type mixer, with lower LO drive and worse IMD
performance. It also is more susceptible to AM on the LO.
73
Peter G3RZP.
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