On Mon, 12 Sep 2005 21:52:01 -0400, TRABEM wrote:

But, if the switch is anywhere near linear, you would not want your
gain stage before the switch, would you?? I can't see using an rf amp
at the antenna that just creates non linearity when you could use a
nice quiet audio amp op amp on the far side of the analog switch.

If you use a huge amplification on a single frequency, you can end up
with stability problems, due to unexpected feedback paths, such as a
direct conversion receiver with a lot of audio gain started to
oscillate, when the loudspeaker sound vibration was connected back to
some front end component that was microphonic.

Putting a (possibly switchable) preamplifier between the selective
loop and the mixer would allow some gain to be done at non-audio
frequencies, thus, reducing the risk for stability problems.

Paul OH3LWR