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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