Until recently, I have been using my HFPacker 35-50W amplifier with my
K2, KX1, and other QRP rigs, all going out to an LDG Z100 tuner.
In the shack the Z100 was having trouble matching my doublet on some
bands, but the K2's had KAT2 never had a problem, so I decided to try
a KAT100 to get better response and also avoid having to retune and
switch the KAT2 in and out when going QRP or QRO.
There is one gotcha in using the KAT100 with a non-Elecraft amplifier:
when in place, the KAT100 provides the power measurement to the K2,
and so the power control operates over the whole system. In other
words, the K2's power pot setting is being checked against the output
power of the amplifier, not the output power of the K2. This works FB
with the KPA100 (as you might expect) but with a non-Elecraft
amplifier, it doesn't, because without a KPA100 plugged in, the K2's
power knob still stops at 15W.
I explored this issue with Gary AB7MY who very patiently worked
through the scenarios with me, and I wound up taking his suggestion to
unsolder the VRFDET line at the KAT100 end of the IO cable. That
caused the K2 to use its internal RF metering (in my case the KAT2) to
measure the K2's output, and I can set it to 2.5W like I did before.
Now I have can leave the KAT100 in place and not have to retune when
switching the amplifier in and out, nor worry about whether I've got a
match. The Z100 will still have a place in my shack and my pack for
higher power for my other rigs, but for the K2, the KAT100 works FB
and matches my doublet on the bands that the Z100 had trouble on.
Thanks to Gary!
Leigh / WA5ZNU
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