Elecraft KXPA100 Manual - Manual (Page 46)

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Appendix A: ALC Adjustment
Transceivers such as the Yaesu FT-817 that provide output power control in large discrete steps depend upon
the ALC system in the KXPA100 to limit the output to 100 watts. The KXPA100 Automatic Level Control
(ALC) must be adjusted as follows to provide the correct level of control for your transceiver power level.
Transceivers that provide fine control of the output power in 0.1 watt steps or less do not
need this adjustment. That includes all of the Elecraft transceivers including the KX3.
There is no advantage or benefit from performing this procedure for those transceivers.
Check your KXPA100 amplifier to see if there is a hole cover on the side just below the handle (see Figure 16).
If so, pry the hole cover off. A small screwdriver adjust potentiometer will be visible just inside the hole. That is
the ALC adjustment. If there is no hole cover on the side of the KXPA100, remove the bottom cover as
described on page 47 to access the potentiometer.
Figure 16. ALC Adjustment Potentiometer Location.
Adjusting the KXPA ALC
You will need a 50 ohm dummy load capable of handling 100 watts for short periods of time and a screwdriver
with a thin blade about 1/16” (2 mm) wide to adjust the ALC potentiometer. A screwdriver with a metal blade
may be used. An adjustment tool with the blade inside a tube so it cannot easily slip of f of the screw is ideal.
Adjust the ALC potentiometer as follows:
Connect your amplifier for normal operation with your transceiver (see Amplifier Connections using the
FT-817 Interface Cable on page 16 or Amplifier Connections for Basic Operation on page 18). Connect the
KXPA100 output to a dummy load.
If you removed the bottom cover, be sure you have not dislodged any of the TMP
connectors on the coaxial cables that attach to the pc boards in the KXPA100 (see Figure
20. Rear Panel RF Cable Connections with ATU. on page 50 or Figure 21. Rear Panel RF
Cable Connections with No ATU. on page 51).