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<DIV><FONT face=Arial size=2><STRONG>I sent a couple of my ham buddies some of
the recent LCC email postings and thought I'd share their thoughts with
you. They're okay with the idea of sharing this.</STRONG></FONT></DIV>
<DIV><STRONG>Randy K4LJA</STRONG></DIV>
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---------------------------------------------------------------------------------------</STRONG></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>FROM TOM WEBB; W4YOK:</STRONG></FONT></DIV>
<DIV><FONT face=Arial><BR><FONT
size=2><STRONG></STRONG></FONT></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>> >Charles Harpole, K4VUD, brought
his K3 over to my shack a while <BR>>>back. Now maybe we were doing
something wrong, but we connected the <BR>>>K3 in parallel with a coax tee
with my Drake R-4C and tuned in a <BR>>>very weak signal on 40 CW which we
could copy on the R-4C, but which <BR>>>was inaudible on the K3. No
amount of knob twisting could bring the <BR>>>signal up out of the noise
on the K3.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>REPLY FROM RANDY FARMER, W8FN:<BR>>
<BR>> Charlie's (very early) K3 must have had something wrong with it. I
<BR>> know he had lots of issues with the AGC settings when he first got
<BR>> the radio. It may seem counterintuitive, but running up the gain and
<BR>> turning on the preamp is NOT the way to hear signals near the noise
<BR>> floor, especially on the low bands. High gain together with an overly
<BR>> aggressive AGC just lets the noise control the AGC action and greatly
<BR>> reduces the signal to noise ratio of weak signals. Low sensitivity is
<BR>> certainly not a problem with the K3, especially on 40 meters where
<BR>> the band noise is usually around 20-30 dB above the receiver noise
<BR>> floor with any kind of an antenna at all.<BR>> <BR>> I normally
run the RF gain (which is really an IF gain control) down <BR>> to where the
band noise just barely doesn't cause the signal strength <BR>> indicator to
fluctuate. Most of the time this is anywhere from <BR>> indicated S3 to S7 on
40 meters here. I've set my AGC Threshold to <BR>> 008, which puts the onset
of AGC action at around -100 dBm. I've set <BR>> my AGC Slope to 001, which
allows an audio output change of around 4 <BR>> dB for every 10 dB of signal
input increase once the AGC kicks in. <BR>> These settings keep the output
level nearly proportional to the input <BR>> level up to around -50 dBm,
where the hardware AGC kicks in to <BR>> protect the A/D in the DSP section.
This setup maximizes dynamic <BR>> range in the audio and provides the best
readability of weak signals <BR>> in the presence of big QRM or noise. In big
contests I usually end up <BR>> switching in the attenuator (the RF gain
control) on 40 to keep the <BR>> huge signals under control, and I have yet
to have any problem <BR>> pulling very weak signals out of the QRM. Of course
once a weak <BR>> signal is truly buried in the noise no kind of receiver is
ever going <BR>> to be able to improve the S/N ratio so you can hear it. Once
the S/N <BR>> is 0 dB the signal is by definition covered by noise.<BR>>
<BR>> The K3 has lots of adjustments you can twiddle to make it do what you
<BR>> want, and taking the time to adjust things like the AGC behavior and
<BR>> the overall gain can make the difference between hearing and not
<BR>> hearing weak signals in difficult conditions. The K3 runs circles
<BR>> around my modified R-4C, and that's really saying something.<BR>>
<BR>> 73...<BR>> Randy, W8FN
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