[Elecraft] K3 power loss on 10 meter USB

[Don Nelson]

During the 2008 10 meter contest this past weekend I experienced some power
loss during USB transmissions. The K3 was set to 100 watts, more or less.
The K3 firmware is the 2.58/1.94  vintage. In responding to another party
calling CQ I would send my call sign, N0YE. The N0 would be transmitted at
the full 100 watts. The YE would be transmitted at about 10 watts. The power
level observations were made on the built in power indicator in the K3. This
behavior was highly repeatable. The K3 would transmit about 4 syllables of
speech at full power and drop to a low power there after. This behavior
occurred with whatever I spoke while transmitting.

I used more than one antenna during the contest. Each antenna had it's own
tuner and so the K3 antenna tuner was bypassed. I can not say for certain
that the SWR to the rig was always better than 2:1.

I do not know what I can do to get the K3 into this abnormal operational
state. And I am not totally sure how I got the K3 into a “normal” operating
state. I think changing power levels is one trigger to get into this
abnormal state. I think going into the TUNE mode for a while is a way to get
in the normal state. I also think changing bands say from 10m to 12m and
back to 10m without transmitting is another way to get to the normal state.
Power cycling the K3 may be another way to get to the normal state. Once in
the normal mode, the K3 would function normally for a long time.

After I built the K3 kit, I experienced power fluctuations while
transmitting. These fluctuations were cured by grounding pins 7 and 8 onto
the MIC connector shell. The K3 has functioned normally on 40m, 20m, 17m and
15m bands since that fix. The modified MIC connector was used during this
contest. This other problem and fix are mentioned in the off chance there
may be a connection to this 10m transmit power problem.

So my questions to the group are:  Is this a problem observed by others? Is
this a solved problem? If this is not a solved problem, are there things I
could do to mitigate the problem?

Don, N0YE

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