I had my threshold set to 2 uv on the Orion when I did this in order to not
get any AGC action with no antenna. If I put the threshold at 0.37 uv, then
the DSP agc action brought up the receiver noise above the antenna noise.
You could tell it was AGC action causing the noise with no antenna and
threshold at 0.37 uv because there was a slight delay when switching out the
antenna before the noise came on. So that is why I adjusted the threshold
to 2 uv. I was also using the 2.4 khz filter when I did this test. This
test is very dependent on how much noise the antenna is picking up at the
time of test but still has some validity. Any increase in noise when you
connect the antenna indicates your receiver has enough gain for the current
conditions.
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "Jim Reid" <jimr.reid@verizon.net>
To: <tentec@contesting.com>
Sent: Sunday, February 08, 2004 10:27 PM
Subject: Re: More Re: [TenTec] Orion redefines the meaning of ... AGC OFF
> Carl, N4PY, wrote, in part:
>
>
> > Same test with Orion at 28.6 mhz and preamp off. Large
> > difference in background noise with antenna connected
> > verses not connected. The Orion has more than enough
> > overall gain. And by the way, I am at a very quiet
> > location out in the country here. I am using my 8 element log
> > periodic at 22 meters for the antenna for this test.
>
> Using my Force 12 C3, 2 elements on 10 meters, I cannot
> repeat what Carl has reported; however, with my BigIR
> vertical tuned to 10 meters I can ! In order to hear a noise
> increase with the C3, I must have the preamp ON. I have
> the AGC threshold set fairly high 50 uV, as I assume that means
> no AGC action anywhere near the antenna input noise level,
> corrent? Or, should I have the threshold very low instead?
>
> Not sure if all the above says is that the vertical has a much
> higher noise level than the C3, or that my particular Orion
> does not have enough gain, as Carl reports his evidently has.
> Or, perhaps the log periodic inputs more noise than my little
> C3?
>
> A bit confused about all this now, hi.
>
> 73, Jim KH7M
>
>
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