K3 - AF/RF Gain [and S-meters]

[Edward R Cole]

Fred,

I really appreciate your comments.  I have yet change my default
settings (other than EQ on Tx), so this is very interesting.  I
wonder how you adjusted AGC to noise level threshold?  Seems that
would change with band.  (reply off reflector)

On HF the K3 noise floor ranges from S6-7 on 160m to almost nothing
on 10m.  On 6m I run a preamp so that shoves the noise floor up to
S5-6 (PRE-off).  I could lower 6m using the ATT but that seems
counter-productive to using a preamp (gain=24 dB).

Since my main CW interest is on eme the adjustment would need to be
made with the noise floor presented using a transverter.  I probably
could get all of them adjusted to the same IF level into the K3 (I
try for S1).  My transverters have adjustable IF gain.

Regarding weak CW, I share the same experience using passband width,
APF, notch and NR.

73, Ed - KL7UW

------------------------------

Message: 4
Date: Thu, 19 May 2011 16:59:04 -0700
From: Fred Jensen <[hidden email]>
Subject: [Elecraft] K3 - AF/RF Gain [and S-meters]
To: Elecraft Reflector <[hidden email]>
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Lots of good info comes from this list.  I segregated all the recent
"How to set AF and RF Gains" postings to try and see if I'm missing
something since other than the EQ settings [K9YC's for SSB TX and "try
to emulate my hearing aid response" for RX], I run pretty much
out-of-the-box-defaults, AGC on, RF max, AF for volume, and am a really
happy ham.

In olden days, which have been mentioned here a lot, we ran CW [and SSB
unless you had a new receiver with a product detector] with AF gain
firewalled and RF gain for adjustment.  The reason for this, although no
longer valid with a K3, was to equalize the signal and the BFO injection
amplitudes.  Minimum distortion occurred when they were about equal, the
BFO amplitude was fixed, so you adjusted the signal level through the
receiver to sort of the same amplitude.  The right point was fairly
obvious.  The S-meter followed the RF gain control ... that's just how
it was.

AGC used to be a somewhat brute force thing ... 1st mixers had to be
protected so the AGC line hit the RF stage(s) as well as the IF's.
SX-28?  My K3 seems to have an exquisitely designed AGC system [well,
more than one].  I run with it on, I've tweaked the threshold so it's at
my normal noise floor, and my RF gain is at max.

I cannot tell any difference between my ability to copy very weak CW
signals in my normal configuration, and when trying to ride RF gain.  In
light of all the reflector chatter on this subject, I've tried to make
this work [I'm retired, I have time :-)].  The WIDTH knob can help, the
APF function can be a big help under some circumstances [not all], and
very occasionally, the manual NOTCH will make a difference.  Other than
that, it seems letting my K3 do its job by itself, AGC on, RF max, AF
for volume, works best.

What am I missing here?

For the record, my K3/100 is pretty vanilla:  One Rx, "stock" filters,
KDVR, KAT3.  I have several locals within 3km of me, their rigs are very
quiet on CW, they are the only signals that get much above S9+20, and I
can get well within 1 KHz of them in contests and still work the weak
ones.  They haven't complained, I hope I'm not getting too close :-)  I
don't operate SSB a lot, usually only in contests to support my contest
club.  If that's what this is all about, I apologize for the BW.  If
it's CW, I'm either missing something or I guess I'm less discriminating
that most.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org





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