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Do you have any Serial Number Range of units affected? I've
been through 2 KPA3A assemblies, with the 3rd now in the radio
since May of this year. The radio was purchased new from Elecraft
in August 2015. The serial number is 10163.
On 10/28/2018 8:36 PM, Randy Farmer
Hi, Jeff. I encountered the same problem. My
early production K3S PA was going into parasitic oscillation at
low powers on 80 meters. The out-of-band spurious causes the
high SWR indication. According to Elecraft Service this is a known problem
with the first run of KPA3A boards. They sent me a new KPA3A
module to swap in and that cured the problem. It's possible your
K3 may be doing the same thing.
On 10/28/2018 7:52 PM, Richard
Williams via Groups.Io wrote:
Did you try
transmitting into a dummy load? If you have no issue with a
dummy load, start looking at RF feedback into the radio.
On Sun, Oct 28, 2018 at 17:59, Jeff Clarke
I'm running a K3-100/KPA500 on 80
meters thru a Denton antenna tuner feeding a 135 center
fed zepp with 450 ohm feeder. I'm having a strange
With the KPA500 powered off and slowly increasing the
drive on the K3 up to 13 watts the SWR is OK. It goes
sky high (above 13 watts) when the internal 100 watt amp
in the radio kicks in. It starts to go back down (normal
SWR) as I continue to increase the drive on the radio.
The SWR seems to return to normal when I get it up to
about 50 watts or so. Unfortunately this is too much
power to drive the amp and it faults.
When I turn on the power for KPA500 and put it into
standby I get the same symptoms I described above. When
I take it out of standby it looks like everything is
working normal... but I'm not sure if having the amp on
is really solving the issue because there still is a SWR
issue somewhere? I also removed the KPA500 completely
out of the circuit ( to see if it was the problem) and
plugged the antenna directly into the K3-100 and the
symptom comes back. I also hooked up my spare IC756Pro2
to the KPA500 and tuner and it appears everything works
OK. So I don't think the problem is with the amp.
The K3-100/ KPA500 combination seems to work fine on all
the other bands. All those other antennas are resonant
and don't go thru the antenna tuner and zepp that I use
for 80 meters.
Any ideas on what might be going on?
Thanks, Jeff KU8E