RF gain sweet spot

[Edward R Cole]

I'm guessing this "effect" is an artifact of the AGC parameters and
the level of ambient noise.  I would love to see a chart of AGC
level, K3 gain, and RFG bias voltage.

I see a flat zone between RFG at maximum and at 3-o'clock position
when I either have no preamps activated and when I activate the PRE
(internal preamp).  Gain appears flat over that range and I hear no
change in audio level with antenna connected.  Remember that I have
extreme hearing loss so it may mean I unable to hear the change even
if there is one.

When I run my ARR preamp, the s-meter indicates S4.5-S5 and the
s-meter immediately rises when I rotate the RFG to a lower
setting.  There is no flat region.  Since my preamp has 24-dB gain
and K7WIA is using a preamp with 15-dB gain, they are not exactly
compariable.  The approx. 9-dB extra gain may be saturating the
follow on Rx circuits.

A precise measurement of SNR (with a weak signal) vs RFG voltage
would be interesting.

Perhaps Eric or Wayne will comment.


73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-100w, 1296-60w, 3400-?
DUBUS Magazine USA Rep [hidden email]
======================================

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[KD7PY]

Hi Ed..    I just did a check using the XG3.   tap the disp button to display AFV
I do not see a drop in voltage untill I turn the RF knob to about the 3:00 o'clock position.....
so it seams that untill the RF knob gets to there,  there is no gain reduction untill we get past that point.
and at the point I start to see a reduction of AFV,  the S Meter just starts to do its dip, it will go down a small bit more and then start to climb up as  I reduce the gain more....

Ed K7WIA