I am going to go off on a wild tangent as a method of testing all
receivers for the ability to copy signals in the midst of very crowded
band conditions and/or the presence of noise. Whether those receivers
have analog front ends or an ADC.
An extremely crowded band could be simulated by broadband noise.
So take a medium strength single signal (say S-5) and inject it into the
receiver under test.
Now add a low amplitude broadband noise signal, and increase it until
the signal is buried in the broadband noise.
The receiver that can withstand the greater broadband noise level while
still recognizing the single signal "wins".
That says nothing about the overload of the ADC for those receivers that
put the ADC at the antenna - that is something for other test parameters.
73,
Don W3FPR
On 9/15/2015 6:28 PM, Jim Brown wrote:
On Tue,9/15/2015 1:52 PM, Tony Estep wrote:
On Tue, Sep 15, 2015 at 3:36 PM, Joe Subich, W4TV <[email protected]>
wrote:
....noise power ratio testing hides the fact by not providing MDS
values under each test condition *and* fails to indicate that even
with *no preamplifier* the total noise signal is more than 10 dB
*less*...
=========
I take this to mean that the test results are not comparable across
radios, and the SDRs are 10db worse than they show up on the
comparison chart. If this is true, it ain't good.
You've got the concept right -- the only difference is that 10 dB is
not a "hard" number -- it could be anything from 5 to 30 dB, depending
on how much test signal strength has been turned down, or preamp gain
removed, to get the input of the digital system out of clip!
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