"ken scharf" wrote in message
news:RoADk.41384
ken scharf wrote:

What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

The conversion gain should be much greater than unity
for any of those balanced mixers. He was doing
something wrong to write statements like those.

Regarding the DBMs, sure they have some loss,
but the losses basically sets the mixer noise figure.
Add a few dB loss for the the front-end preselector
filtering, and may 8 dB loss for the mixer, followed
by a strong, low noise IF amplifier, and your pretty
much good to go, on the HF bands anyway..

DBMs like to be driven by symmetrical
LO waveforms (square wave is great) and the port
terminations are critical as well. My own experience
with them is that the supporting stages also need good
shielding, filtering and bypassing, they are great
harmonic mixers from DC to light!

I'm sure Bob's H-Ring designs are suberb; I've
pretty stopped playing with mixer circuits after the
DBMs became available well over 20 years ago!

Pete