"Michael Dunn" wrote in message
.. .
In article , Doug Smith W9WI
wrote:
What is your reception goal for this receiver?

- High fidelity?

- High sensitivity?

- Adjacent-channel rejection?

- Overload tolerance?


Pretty much all of the above. Cost is secondary. Though I do like
simple elegance, and I'm not going to go as far as the SUPRX mentioned
by Bob, though it must be a fine rcvr.

Mark mentioned:
could design not only AFC, but also automatic tuning of an RF
preselector and perhaps even an antenna tuner, that would be tres
cool.

All of my older FM tuners have a three-gang "bread slicer", A.K.A. variable
capacitor. It tunes (1) the LO, (2) mixer input, (3) RF stage input. Since
the OP wasn't interested in a synthesized LO, a multigang capacitor would
seem to make sense.

With some imagination, one could arrange a scheme so that the LO would lock
to
a synthesized signal every 200 kHz step. Thus one-knob tuning of multiple
stages, yet with synthesizer stability. Details are left as a student
exercise.

73 de bob w3otc

"R J Carpenter" wrote in message ...

All of my older FM tuners have a three-gang "bread slicer", A.K.A. variable
capacitor. It tunes (1) the LO, (2) mixer input, (3) RF stage input. Since
the OP wasn't interested in a synthesized LO, a multigang capacitor would
seem to make sense.

With some imagination, one could arrange a scheme so that the LO would lock
to
a synthesized signal every 200 kHz step. Thus one-knob tuning of multiple
stages, yet with synthesizer stability. Details are left as a student
exercise.

73 de bob w3otc

You'd also probably get higher Q with air var. cap.
But everything else is more complicated with this approach

SioL