I must be missing something in this recurring "RF Gain" thread. In the
"olden days" before product detectors [think SX-28], for CW, you turned
AGC off, AF gain to max, and used the RF gain. The BFO produced a
constant signal that activated the AGC if it was on, and with the RF
gain at max, the received signal was way too high at the mixer compared
to the BFO level which was constant. The S-meter didn't work for CW and
that funny sounding new mode called SSB.
Today, I run my K3 with RF gain at max, AF gain controls the volume, AGC
is on ... SLOW for SSB, FAST for CW ... all the time. After all the
comments in this thread, I've tried "riding the RF gain" with AGC off on
very weak signals. CW signal readability doesn't change. If I could
barely copy him with AGC on, I can equally barely copy him without AGC.
The only effects I can find are: 1) I'm fiddling with the controls a
whole lot more and if QSB occurs he disappears until I manage to bring
up the gain; and 2) A strong station that appears in the passband is
really really loud in the cans.
I leave my P3 set with dBm on the ordinate. Except on RTTY, the P3
averaging prevents the apparent peaks from actually matching the peaks
on the S-meter and I kind of like to see the real baseline noise level
at the receiver input.
Based on this thread, I must be doing something really wrong. My K3's
AGC does a super job of controlling the RF gain, far better than I can
do manually, and my S-meter works in all modes. Explanations on what
I'm missing are welcome.
My "rememberer" remembers a receiver that had both a real RF gain
control and an IF gain control separately. I don't remember the name
however. I'll look in Fred Cady's book this afternoon and see if the K3
HW AGC is actually applied to the RF stage [not sure there is one], the
first mixer, or just the first IF amp chain. I remember audio-derived
AGC ... it was OK for phone, not so much so for CW.
73,
Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org
On 3/11/2013 3:08 AM, Mike Rodgers wrote:
By the way, I don't want to incur the cost of a P3 to "fix" the RF Gain PAIN.
I'm just having to live with it.
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