I am not sure how much the RF amp adds to the noise level.
A well designed rf amp section can actually reduce noise levels.
Noise mostly comes from mixers, and overall tube counts.
All mixers add some noise, some designs are much better than others,
and the more there are, the more noise you get.
I used single conversion, with a quiet mixer setup, and
used two tuned circuits of very high Q in the input,
along with resonant dipole antennas for 80 and 40 meters,
so I don't get any images or other problems, as signals
out of band are attenuated very much before making it to
the mixer.
I think the best mixer designed ever developed used the 7360 or similar beam
deflection tube. I'd like other opinions on the subject, if anyone thinks
there is anything else that actually surpasses the performance of these
tubes in mixer service?
Don K4KYV
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