The K2/100 has two ALC circuits. One is found on the K2 Control Board
(MAX534). This ALC works in the CW mode. The other is found on the KSB2 Board
and works in the SSB mode. This is the Tracking Automatic Level Control
(TALC). Tuning up a QRO amp by holding the K2 TUNE and RF/ALC buttons (in any
mode) produces the correct amount of CW RF power from the K2/100 for the
desired QRO output. To obtain the same desired SSB peak power output it is
necessary to turn the POWER control down.
I have the PSK31 KSB2 ALC Time Constant Change Mod installed, but John
Grebenkemper (KI6WX) says he does not think the change in time constant would
be an issue. He says this mod was designed to increase the hold time for the
TALC to what is used in most transceivers.
I understand the complexities of measuring peak sideband power so it can be
assumed there is a certain amount of error in the reading. With that said I
still wonder why these two ALC circuits don't more closely track each other for
the same POWER control setting. Thirty five watts in the CW mode results in
1000 watts of output in my case. Fifteen watts of modulated SSB results in
1000 peak watts. I would like to know if others using QRO amps find similar
amount of variance in the POWER control. Thanks. Roy Morris W4WFB
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