[Elecraft] KAT3 ATU Problem

[Michael Carter]

Tom,

Glad that the MotherShip is helping out directly!

It wouldn't have occurred to me to look at
the LPA stage as a source of trouble, but if
the TX power is ramping up slowly, then I can
see where the ATU control algorithm is
confused by the change in power levels both
forward and reflected.  My ATU seems to
change relay settings very fast, and the control
algorithm is looking at change direction (maybe
change magnitude as well) in SWR to decide
which relays to flip next.  The relative adaptation
speed of the control algorithm and the TX power
ramp-up could certainly cause interactions that
might slow the ATU convergence, but I would
think that once the TX output power stabilized,
the ATU control algorithm would be receiving
valid SWR readings as it flips relays.

When you say it takes seconds to ramp up
to full (TUNE) output power, does this happen
on every TUNE button press?  Does it also occur
when you send CW from the paddle/key? Can
you watch the RF envelope on a scope to time
the power ramp-up?

73,
Mike, K8CN