> rig X= MDS at 80 meters-128, MDS at 20 meters-139,
> Blocking DR at 80 meters 115, Blocking DR at 20 meters 125
> IMD DR at 80 meters 94, IMD at 20 meters 90
> rig Y= MDS at 80 meters-127, MDS at 20 meters-124,
> Blocking DR at 80 meters 117, Blocking DR at 20 meters - (?),
> IMD DR at 80 meters 84, IMD DR at 20 meters 80
Well, rig X certainly shows very high sensitivity on 20
meters. However, the 15 dB delta better than rig Y may
be comparing an apple to an orange. You must know
what bandwidth of IF was being used! The -139 dB
number must have been using at least a 500 Hz CW
filter, maybe even a 250 Hz bandwidth, and a test
of CW or steady tone minimum signal. The
MDS signal level method should also be explained:
was this a signal+noise oscilloscope measurement,
just able, maybe to see a slight blip above the noise,
or, sometimes a hole in the bottom of the noise just
above the base band line of the scope? Or was the
bottom of the signal brought up to be tangential with
the average top level of the noise spectrum? This is
usually described as a 3 dB signal to noise ratio.
Important to know that both rigs were tested
exactly the same way.
More to specs than just the numbers, hi.
Rig Y just might have been using a much
wider IF bandwidth for the noise level to have been
15 dB higher, in my opinion anyway, hi.
Does your source list the effective IF bandwidths used
to measure these numbers? It is very important to know
in order to do a valid comparison.
Just my thoughts, and may not be quite correct
in detail, hi.
73, Jim, KH7M
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