This is a great discussion. I truly appreciate Bob's latest entry.
Some time ago on this list, someone posted a message that suggested
using the menus to set the AGC threshold such that the S-meter
doesn't move due to band noise. Then, AF gain to some comfortable
level and use the RF gain for fine adjustments to whatever particular
situation you might come across, and start workin' em.
What followed was some discussion about how doing this distributes
the gain differently within the receiver system and how simply riding
the RF gain doesn't distribute system gain as optimally as setting
the AGC threshold does.
I find this latter sort of knobology far more manageable than "AF
gain to max, ride RF gain" on the O II, for at least two reasons: 1)
there is no dedicated RF gain knob, so I have to punch lots of
buttons all the time, and 2) I'm left wide open to being blasted by
strong signals or feedback, just as Bob warned. I've been using the
"adjust AGC threshold" method for some time with good results, though
not under full-battle contest conditions.
I don't yet understand all the intricacies of how and why gain is
distributed as it is throughout the receive system, but I hope to get
a handle on it as time passes. My guess is that all of these
approaches result in similar (though not identical) performance. In
fact, I'll wager that different combinations of the "adjust AGC
threshold" and "run with AF high, ride RF" approaches are optimal for
any given condition.
Kim Elmore, N5OP
At 08:18 AM 2/2/2008, you wrote:
This has been an interesting discussion alright.
I have spent quite a bit of time experimenting with different settings
of af gain/rf gain/agc using an Orion II with latest firmware.
My observations have been that the difference in readability of a weak
cw dx station has for me been minimal by increasing af gain and riding
the rf gain regardless of agc settings.
It does not seem to alter the s/n ratio between the weak cw station and
the atmospheric noise much at all, if any.
Perhaps this is because I am using a vertical antenna that may be more
noise susceptible?
The difficulty I have with minimal agc and high af/low rf gain is that
as soon as the dx station signs, a very strong station calls and just
about blasts me across the room before I can get the rf gain down.
Advice please?
Tnx & 73,
Wayne
--
Wayne Whitman
Cell:270-282-3550
wwhitman@fastmail.fm
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