Interesting subject. I switched back to 1.372 for the original Orion, which
seems more stable than 1.737b(5). Since tentec found and replaced a bad relay
I have had NO hangups, no firmware bugs bothering me, and no resets. It has
been almost 2 months.
For roundtables on 75 meters, for example, just operate like any dim bulb --
turn up the "rf gain" knob until you hear noise on the band, and then let the
AGC take care of it. You don't need to ride the RF gain. Turn off the preamp
and use the attenuator if necessary. You might want to use the NR if the noise
is extreme.
For cw dx on a fairly quiet 20-meter band, turn on the preamp, take the rf gain
down on each signal you work to find the "sweet spot" where the noise is
minimized but the signal still creeps thru. Narrow the bandwidth as well to
lessen the noise. Using the NR in this situation is not preferable to a combo
of bandwidth / rf gain usage.
That is, if you are using version 1 of the code. I have no idea of proper
operation of the Orion with ver.2 software. --brent N9HZ
From: John Huffman <hjohnc@gmail.com>
Date: 2008/05/11 Sun PM 06:14:57 CDT
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] AGC Threshold, RF Gain, Volume
Thanks Merle!
That was a good explanation of what I was experiencing. I like version 2
firmware, but will try v1.373b5. I've tried it before, but never for long
enough to get used to it.
73 de K1ESE
John
----- Original Message -----
From: "Merle Bone" <merlebone@charter.net>
To: <tentec@contesting.com>
Sent: Sunday, May 11, 2008 3:15 PM
Subject: [TenTec] AGC Threshold, RF Gain, Volume
> John,
> Yes the RF gain control changes the AGC threshold level - just like
> setting
> it in the AGC menu. One of the original Orion firmware developers, Doug
> Smith, wrote in a paper describing the Orion Digital AGC System:
> -----------------------------------------------------------------------
>
> "In digital AGC systems, it is relatively easy to provide a variable
> threshold or "knee." Input signals below the threshold do not actuate the
> digital AGC and are not compressed. At thresholds well above the receiver
> noise floor, a receiver therefore gets quiet when only puny input signals
> are present in the passband. At thresholds near the noise floor, all
> signals
> are boosted to meet the output-level criterion. The net effect of a
> variable
> threshold is very much like that of an IF gain control."
> ------------------------------------------------------------------------
>
> Consequently, if you "ride the RF gain" and set it for a good audio level
> on
> a stronger signal, weaker signals will not activate the AGC and they will
> be
> too low in volume. I've never been fond of this process. I think it was a
> "crutch" to offset the gain distribution issues in the new Orion V2
> firmware. There was an AVC loop in the V1 code that prevented the audio
> stages from being overdriven and distorting. That code was taken out of
> the
> V2 firmware and there have been peak signal distortion issues since. That
> started some people doing what you described with the audio and RF gain
> controls. Unfortunately you are seeing some of the unintended consequences
> of operating the radio like that. Hopefully Ten-Tec will address the
> distributed gain level issues in the next Orion V2 firmware release -
> maybe
> they will put the ALC code back.
> 73, Merle - W0EWM
>
>
> _______________________________________________
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> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
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