[Elecraft] K3 Transverter drive problem

[AD6XY - Mike]

I have come across a problem with my K3 driving an XV50 converted to 70MHz. 

The K3 low level output from the KXV3 produces high power spikes before
settling to the correct level - which it then holds until you change mode,
or power setting. It also produces spikes at full power ( a few mW) as you
turn the power knob. When I originally tested the transverter interface, I
used an analogue power meter, so I would not see these spikes. I can see
them clearly on my oscilloscope for a few fractions of a second before the
ALC acts.

The effect is of course for the transverter to over drive and then settle
back. Obviously I am doing something wrong here but I am not sure what it
is. The K2 does not do this but it is making transverter operation
impossible with my K3 until I can find out how to fix it.

The curious thing is the way the spikes appear as you adjust power. It is
like the CPU is forgetting the ALC setting, reading the op-amp output,
thinking for a bit and then setting the correct gain. I must have some
setting set incorrectly.

Mike

PS

The K3 also suffers from the same transverter failure mode as the K2 - if
you power off the radio in a transverter band, the transverter stays on in
transmit mode because of the way the PTT works and because the K3 does not
send an "off" command on the auxbus before shutting down. The result is a
very hot transverter power amplifier module the next morning. Perhaps we
could fix this using one of the digital outputs?


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