I think we got off the original subject of this post, but that's ok. There
are NO problems with the Rx section. No IMD problems, no desense of the Rx
section. Although it is a cheap design, it isn't too bad. At least a
monolithic crystal filter is used as a roofing filter at the 1st I.F. to
protect the 2nd mixer from off-frequency signals. Most of the CB units use a
10.7MHz ceramic filter with a bandwidth of anywhere from 150 to 230kHz,
which is only going to reduce 2nd image response.
Below 30MHz, you don't really need to worry so much about
NF....................a 12dB NF is fine. As long as you are conjucate
matched, stability would be good. The main thing that can cause problems is
if you S11 parameters (input return loss) aren't high enough. If you have at
least a 10dB return loss for both your S11 and S22 parameters, you shouldn't
have any problems. Most RF amplifiers are going to be unilateral, so our S12
(input / output isolation) is going to be at least 25dB. It if isn't, the
designer of the equipment didn't know what he was doing, and doesn't have
any business doing that job in the first place.

Pete

Conjugate match is needed for maximum power transfer. Nuetralization
helps extend stability over various mismatch condistions.

In a receiver RF front end it is preferable to match for best noise
figure and accept the gain. The less gain before the mixer the better.
The RF front end sets the noise figure for the whole receiver. The
gain of the RF Front end need only be high enough to overcome the
noise figure of the next stage and any losses it may present if any.

More often than not,CB calibur radios places far to much gain in the
first stages so that more simple IF stages can be used. Thereby
lowering costs.

james