>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
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.
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