Another factor I have found is that if you are running BW under 300 hz or
so - the NR becomes less effective on CW (there have been many threads about
how the DSP NR is working and this follows those discussions) - also my OII
always requires an increase in RF gain maybe 5 to 7 points or so when the NR
is switched on .I always run AF gain about 2/3 full and set level with RF
gain. I seldom find any condition where anything above NR of 3 helps S+N/N
. But I have copied MANY very weak signals especially on 80 and 160 with NR
1 that I simply could not copy otherwise. QSB makes it somewhat less
effective but still worthwhile to pull out a weak signal.
I do not have extensive use on SSB but at 1.8 to 2.2 khz BW I have been
impressed at how much it helps readability .For instance the SO4R guys on 75
SSB were right at the noise and while I could tell they were in there with
NR off, with NR at 1 or 2 they became copyable well enough to call them.
(And work them with an inverted Vee at 39 feet from AZ) Is it broadcast
quality - no - but copy versus no copy is there.
So everyones experience varies as they say - and there are some noise
conditions that the NR is not as effective for me. From time to time if
bands are not too crowded , and on some types of noise , I find that forcing
the roofing filter to 6 or 12 khz will make the NR MUCH more effective .
Obviously if bands are crowded with big signals this is not useful. I
stumbled onto this effect one evening playing with diversity on weak 160
signals when I noticed that the NR on the SUB rx would wipe out the noise I
had at the time. Opening up the roofing to match the SUB rx roofing made the
NR the same on the MAIN rx.
Everything I have said is with AGC Decay at 80 db/sec , Hang at 0.04 sec
and threshold at 1 uv . My measured data on my O 565 shows threshold is
little different if at all than reducing RF gain. I have not repeated this
on the OII but it seems to act the same - For instance watch the S meter
come up as you reduce RF gain - then set RF gain full and reduce
Threshold - - does the same thing.
My two cents worth - Hank K7HP
----- Original Message -----
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, April 28, 2009 6:08 PM
Subject: Re: [TenTec] Noise and ORION II
> Depending on band conditions and antenna efficiency {not antenna gain}, a
> RF
> Gain value of 60 may be too high. With a 1/2 wave resonant antenna on
> 160M
> and 75M and to some extent, I run the RF gain in the 30's. On 10M & 12M
> more RF gain is required due to the fact the antenna captures less signal.
>
> 73
> Bob, K4TAX
>
>
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