[Elecraft] K3: Strange behavior on 80m

[Luis V. Romero]

All:

In SS this weekend, I noticed something "new" with my K3:

When attempting to transmit a low power tune signal (I'm set for 10 watts
out on tune) below, say 3.520, the power out and swr meters begin to
oscillate wildly.  Going above 3.520, everything looks and works normally.  

If I key the transmitter using the TUNE function (press and hold XMIT), then
sweep the VFO below 3.520, the rig transmits fine at any power level but
does not receive (see below) until I move the vfo, whereupon it starts the
oscillation again.

Listening on the receiver, when I tune below 3.517.70, the receiver stops
hearing anything on the band and what sounds like distorted voice audio from
a local Broadcaster is heard.  I have a 50kw AM Broadcaster 5 miles away on
970kHz, BTW, its their audio that I'm hearing.  Its completely
unintelligible, but I can correlate that it's the same audio when they stop
modulation or go to commercials.  Immediately when passing 3.517.70 going up
in the band, the receiver returns to normal amateur band reception, and the
distorted audio goes completely away.  I have made a recording in case
Elecraft wants to hear what this sounds like.

Tested this on SSB and CW, and find that the change to distorted voice audio
happens at 3.517.70 on cw, 3.519.30 on LSB and 3.516.30 on USB.  This switch
point appears consistent, as I have repeated it several times.  I don't have
the NB or NR on, and turning these on don't change the result.

This is with K3 # 3192 using the recalled beta firmware version 4.18.  I
have not noted this issue before, but to be honest, I don't often use the
low end of 80m in the course of my normal operation.  I came upon this while
looking for stations in SS CW this past weekend.

Anybody else seen this behavior?

I don't know if this has anything to do with the issues experienced with
4.18, but I thought I would report it to make sure all the information is
out there.

I too have found that the transmit audio parameters that I normally used
with 4.14 now sound a bit distorted with 4.18.  I ALWAYS install EVERYTHING
( check all the boxes) on a firmware update, not just the portions that have
changed, as suggested by Eric in his previous email.  I have a direct RS232
connection from a "real" com port on my computer, through a data switch
between my MicroKeyer II and said com port that I use to delegate what
serial connection sees the radio's com port.   

I will be backrevving to 4.14 tonight, but kept 4.18 installed for SS CW.
The new APF, although rather ringy, was extremely useful in grabbing 15m ESP
QRP signals during SS CW.  

I think it's a great first effort by Lyle.  I'm sure further tweaking will
ensue and as everything in the K3, it will just keep getting better.  

-lu-w4lt-
K3 # 3192