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Re: [Orion] AGC/NR Interaction?

To: Gary Tuck <gtuck@mac.com>
Subject: Re: [Orion] AGC/NR Interaction?
From: Joe Giacobello <k2xx@swva.net>
Reply-to: k2xx@swva.net
Date: Wed, 01 Dec 2004 15:32:02 -0500
List-post: <mailto:orion@contesting.com>
Gary, thanks for your input. What you describe may be a part of what I am seeing. Last night I was on 30M and I set the threshold at an acceptable noise level and then activated the NR. It seemed that both the noise and the signal increased by the same amount. In other words, there was no change in S/N; everything just got louder. It was as if the NR setting was negating the AGC threshold setting.

However, on another occasion, under what appeared to be similar conditions, I obtained the expected quieting from the NR when there was either a signal or no signal present. I am not sure what was different about the two conditions. I kept playing with the NR and threshold settings for a while on various signals, but I couldn't identify a consistent pattern of behavior. (I should add that i am running the RF gain wide open and that I'm still using the N4PY interface.) I'll do some more experimenting tonight.

I also operated 80M CW during the test. Unfortunately, I was too lazy to compare my FTKMP with the new 4 KHz roofing filter with the Orion and just used the Orion exclusively. Nevertheless, it was my distinct impression that I had very few problems with QRM from sigs on neighboring frequencies and no signs of overload or IMD or the like.

73, Joe

Gary Tuck wrote:

Joe, I believe the manual states that you can expect the noise level to
 increase a bit in some circumstances when the NR circuit is engaged
 because the Threshold is lowered--the signal to noise level increases
 though. What I've found is that when I turn on NR, you can no longer
 effectively adjust the threshold level in the Rx menu. I may have the
 AGC set to Program adn Threshold at 20uv but when engaging the NR, I
 can turn the multi knob and the Threshold level numbers change but
 there is no change in the noise level, even at 191uv. So, it appears
 to me that the NR circuit makes a Threshold adjustment and then locks
 out the user from adjusting while NR is engaged.

 I have a strange interaction between the NR circuit and Sweep. If I
 turn off my rig with the Sweep engaged and then turn the rig back on,
 the Sweep will freeze every time I turn the NR off. I have to have the
 NR circuit engaged if I want to use Sweep . If I turn Sweep off and
 then turn the rig off and then on, the Sweep and NR both work and
 independently of the others' setting.

 Absolutely a great rig though. I played around in the CW contest in a
 bit of search and pounce for new ones, and I was continually amazed how
 close I could hear a station next to a s9+30db signal. If I turned my
hardware NB off, I often couldn't even tell a pile up was nearby without
 looking at the Sweep display.

Gary




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