Grant, NQ5T, wrote, in part:
> The potential issue you will have with THRESHOLD set in
> the 20uV range is that there is no AGC action on signals
> below that level. So a weak signal at a few fractions of
> a uV for example will indeed sound "weak".
> The lower threshold setting of 1-2 uV or so in your PROG
> setting will do a much better job of leveling the signal strength
> playing field so to speak.
>
> The more folks that work with these settings for optimal
> performance, the more we'll learn. I think it's been very
> interesting so far.
Anyone tried using the AGC OFF setting? Have been using it
a bit in the CQ CWWW. The settings are, when OFF:
Hang: 00.00S
Decay: 1000dB/S (that is FAST!)
Threshold: 00.37 uV (~ -116dBm, or ~ S 2 )
So the DSP AGC tries to level ALL signals to the same
audio volume from just below S 2 up to S9+ a bunch.
Note: out here on Kauai, I contend with no really strong
signals on the bands, even hard to find an S9 unless from
over on Oahu and then only vary occasionally.
Also, try turning the PREAMP OFF, then running the RF
GAIN up and down an see what happens. Try the same
thing with the PREAMP ON. That is, try this with the DSP
AGC OFF, as well as in the Slow, Med, Fast, and Prog
settings.
Wonder how Ed Hare and the techs at the ARRL labs are
going to sort all this out when trying to report IP3 and
IMD free dynamic ranges! Seems to me, just about
everying can impact the numbers, hi. What are the
"correct" parameter settings for apples-to-apples comparison
numbers for IP3, and the various spurious signal free
dynamic ranges.
I believe it would be correct for comparisons to run the tests
with the DSP AGC OFF (thus the parameter numbers above
will control the result) and probably turn the PREAMP OFF,
and leave the RF Gain at 100 as the RF Gain control
can cut the audible signal level way down even with the
RF PREAMP OFF. So the RF gain is not controlling the
RF preamp, but the gain somewhere else in the chain
of events.
73, Jim KH7M
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