Lawrence
Good data!? Please notice that sensitivity relates to our ability to copy a signal in the background (and rig supplied) noise -- not how much audio the receiver can pump into the air.? yes I perceive you already agree.?
how a receiver changes with preamp on and off does vary with how gain is built into the receiver.? a receiver can be 'gain limited' - meaning more gain would improve sensitivity or 'noise limited' - which you can guess means more gain does not improve sensitivity.?
depending upon our latitude, season etc. the background noise does vary.? at lower HF there is more noise in the atmosphere than our receivers can make, this only changes at the upper part of the spectrum.? in a quiet area with little man-made noise it will be interesting to compare the uBITX to receivers having a preamp on 28 MHz.? I am expecting only a small difference, less than one S-unit maybe.
likely many already know this, but QRN is propagated via the ionosphere - often from tropical regions.? cool stuff!
73 Curt
