On Wed, 2007-12-12 at 13:11 -0600, Merle Bone wrote:
> Bob - K4TAX said:
> "On item that I've discovered with the current Omni VII on the desk, thus I
> no longer have the Orion II available, is that the RF Gain must be run
> lower, actually much lower, than one would expect. "
> ----------------------------------------------------------------------------------------------------
> It is certainly true that adjusting the RF Gain on the Orion is important to
> optimize the
> performance. On 20M with a tribander I reduce the RF gain quite a bit -
> while on
> 160M, with a K9AY Loop, I add a pre-amp in front of the Orion (Not required
> on
> V1.373b5 due to the higher overall gain of that firmware over V2.062a).
> However,
> I don't find that I am able to eliminate the "overdriven audio" sound by
> changing the RF
> Gain setting. There was a lot of "juggling" of gain levels in the V2 rewrite
> - and as various
> issues were addressed throughout the 8 production V2 firmware releases. It
> seems that
> may have left one or more of the internal gain levels incorrectly set. A
> careful review/fix of
> remaining issues with the V2 firmware would be most welcome by the
> Orion/Orion II users.
> Merle - W0EWM
> _______________________________________________
In ault analogue radios, over driven audio comes from wimpy AGC. AGC
that's poor due to leaky AGC circuit bypass and time constant
capacitors, sometimes from controlled tubes with grid emission that
opposes the negative AGC voltage or in fancy radios, low gain in the
separate AGC IF amplifier. Is it possible to adjust the AGC threshold to
a bit lower level in some Orion user parameter, e.g. to make the AGC
more sensitive? Manually changing RF or IF stage gain won't affect audio
drive levels because those are inside the AGC loop. The change needs to
be a part of the AGC loop or after and may well be hard coded in the
firmware.
73, Jerry, K0CQ
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