> So DSP makes the noise? If you hear (excessive) noise in the receiver
> with its antenna disconnected or shorted, it is internally generated
> noise by the RX stages. It would mask very weak signals and this
would
> explain the K6SE "weak signal test" poor results. Blaming DSP is lame
> excuse.
I'm not "blaming" DSP, and did not say that DSP "makes the noise".
What I said was that the noise you hear in the audio output when there is
no (meaning no antenna) signal is an "artifact" of the AGC controlled
digital IF. And that, is not an excuse, lame or otherwise.
The "gain" through the DSP IF stages is very high, when THRESHOLD is
low and there are no signals present. You can see what happens
yourself if you adjust THRESHOLD up. The noise will decrease
significantly because the DSP IF gain/compression point changes. I think
this has also been described in the manual, in the discussion of weak
signal optimization, the effects of NR on THRESHOLD, etc.
Seems to me we've got to stop thinking of the digital AGC controlled IF
stages as just a digital version of an analog IF. It behaves differently.
Do I know enough about the specifics of the DSP algorithms to tell you
precisely why? No. Does it? Most certainly.
I'll repeat it again, because there is nothing I've observed to alter my
conclusion -- the "noise" you hear when there's no antenna connected is
not indicative of high front end noise in the Orion. There is absolutely no
evidence I'm aware of that bears out that conclusion, and others who
have done quite a bit of testing seem to find no issues with weak signal
performance when there is actually a signal source.
As for K6SE's tests, I said what I had to say .. way too much .. :-) about
those a long time ago, and my view of their validity has not changed --
particularly in light of what all of us have learned about optimizing weak
signal performance in the Orion since that fiasco.
Grant/NQ5T
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