[Elecraft] K3 AGC Mod Test This Weekend

[Dave Hachadorian]

Here are what I consider to be the best contest CW settings for
the K3:

config AF GAIN = HIGH (to increase overall post-AGC gain)
config AGC DCY = SOFT
config AGC HLD = 0.20
config AGC PLS = NOR
config AGC SLP = 000 (steepest)
config AGC THR = 008 (highest)
config AGC - F = 200 (fastest)
config AGC - S = 020
Front panel select AGC FAST
Front panel AF GAIN as loud as your ears can stand, 3 o'clock for
   me.
Attenuator definitely ON, and preamp OFF for 160 (unless using
   separate RX antenna).
Front Panel RF Gain set to show 1 or 2 S-units of band noise
   meter wiggle (about 1 o'clock for me)

I know that selecting AGC SLOW on the front panel is supposed to
reduce IMD, but for me, the mushiness is due to the
aggressiveness of the K3's AGC curve, not IMD.  Slow AGC
also introduces desensing due to static crashes and other loud
transients, so is undesirable for that reason.

My next experiment will be to have an N1MM logging program
macro available to send RF Gain command RG090 if a loud
pileup shows up.  RF Gain will be returned to 200 by appending
the RG200 command to the "thank you" message.  This should
be the ultimate in "riding the RF gain control."


Dave Hachadorian, K6LL
Yuma, AZ





-----Original Message----- 
From: Dennis
Sent: Wednesday, December 14, 2011 2:53 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] K3 AGC Mod Test This Weekend

This weekend I will be participating in the Stew Perry 160M
contest, as
will many of you.
For the contest, I've arranged to do some testing of the IMD Mod
as put
forth by N6KR in
a recent email.  I will have two K3s available, one with the IMD
mod
(2uf in parallel with the
.1uf already on the pcb) and one without the mod.  The audio from
each
will be run to
a sound card and one radio will be on the left channel, and the
other
radio on the right channel,
so it will be easy to compare the two audio streams.

K3s will be setup as follows:
Same MCU and DSP firmware
AGC parameters:
DCY  Soft
HLD   .30
PLS   Nor
SLP   000
THR   008
F       120
S       020
AGC as selected using front panel push button will be "slow".
All RxEq will be flat, ie. 0
Preamp Off
Att- haven't decided on this yet, but both radios will be the
same.
Crystal Filter- 400Hz
Bandwidth setting- 400Hz
Headphone audio from an SO2R Box will be routed to the sound card
for
recording.
     The program I use to record the audio will give me 1-hour
wav files.
RF gain adjusted to same number on both radios via N1MM Cat
command
Main Antenna will go through K3(1) Ant 1 jack
K3(1) Ant Out will go to K3(2) Ant 1 Jack
K3(2) will have power reduced to zero and in TEST mode
K3(2) will also be put into transmit mode, but not keyed, when
K3(1) is
transmitting
     by using N1MM Cat commands {CAT2ASC TX;} CQ SP W1UE W1UE
{CAT2ASC RX;}

By putting K3(2) into Tx mode when keying K3(1), I'm figuring the
front
ends on both radios
will not be damaged.  The antenna in use will be a 160M 4-square,
so I'm
confident there
will be plenty of signal for both rigs.  If there is a better way
to do
this, I'm listening.

So that I don't have to listen to 14 hours of audio to find some
"mush",
I will also be
keeping a log of the times when I do hear it.  I'm particularly
interested to see if I can
actually hear the difference in audio from this reduction in IMD.

Comments as to my setup, and suggestions on other things that I
may want
to standardize,
are appreciated.

Dennis W1UE







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