To the group amplifier gurus:
I have been (happily) using an IC-705 to drive my KXPA100AT or my KPA500
with virtually no problems for about 2 months now.
Set up is an IC-705 driving either a KXPA100AT or a KPA500. The keyline to
the amplifiers is a 1/8" stereo plug cable from the send/alc jack of the rig
to an RCA plug on either amp. Mostly use other radio combinations, but
occasionally I use the 705 plus amplifier combinations for simplex D-Star
over HF (DV mode).
The sole issue that has popped up is when using IC-705 for HF D-Star with
the KXPA100AT (regardless of rig frequency). In DV mode and only when I have
a transmit message set, on the initial key up the rig goes into continuous
repeated transmit. This can only be interrupted by pulling the key line to
the amplifier or shutting the rig off. When I disable the TX message, the
rig and the amplifier behave normally in DV mode. The KPA500 does not
exhibit this behavior.
I would love to know what is going on here. Is it something which
transmitting more data than the normal ID data packet that goes with D-Star
voice data causes? It would seem so, but why does the combo continue to
cycle into TX when the data is already sent? Truly odd, but fortunately I
can avoid the problem by remembering to turn off the TX message. When the TX
message is off, the amplifier behaves like a gem.
The KXPA100 switching circuit is likely pin diode based as no relay sounds
can be detected. This is not made clear in the Theory of Operation section
of the user's manual and since there are no circuit diagrams provided, that
can't be verified.
I am forwarding this to Elecraft Customer Service as I understand that I
will not be the first to make the observations.
Thanks for the bandwidth!
Jack Spitznagel - KD4IZ
Science River LLC
Biomedical Consulting Services
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