Tim Wescott wrote:

snip

I doubt that there's any real advantage to feeding a nice clean sine wave to
your MOSFET mixer -- the best distortion performance that you'll get out of
the mixer will be if you're driving it hard (i.e. turning it on and off).
Even with sine waves in you'd get lots of harmonics internally in the mixer.

By the way, why not use an off-the-shelf mixer like the NE602? I doubt that
you'd get much better performance out of a single MOSFET unless you're a
real RF circuits whiz, and the NE602 is quite easy to apply.

snip

I built a short wave receiver many years ago. The design was from a Babani
Press book (highly recommended). It worked OK, but I always hated not knowing
the exact frequency. At the time I had no tools to even calibrate the dial.

The front end was a single transistor oscillator and mixer. I tried the
"improved" design which used a MOSFET, but I didn't have the right Denco coil
and the performance was degraded.

The intention is to add digital tuning to this old project.

--Gary