AUTOMATIC DRIVE LIMITING CONTROL
An adjustable automatic level control (ALC) circuit limits the peak
output power. When properly set, this circuit insures that the amplifier
can not be overdriven. Rear panel access allows for easy manual
adjustment . A sample of the RF input derives the ALC voltage.
Additionally this amplifier has an RF negative feedback resistance in
the cathode circuit to help cancel excessive RF drive without reducing
the amplifier's gain.
A.L.C. ADJUSTMENTS
Your transceiver’s internal ALC will maintain linearity. The amplifier's
ALC will prevent overdriving the amplifier. The HF-2500\HF-2500
MAGNUM's ALC circuit was designed for negative going ALC voltage.
Proper adjustment is as follows:
1. Use an insulated tool when making these adjustments.
2. Tune the amplifier for operation on the 20 meter band for full
1500 watts output.
3. With your transceiver set for 20 meter SSB operation, set the
transceiver's microphone
gain for normal operation as specified in its
owners manual.
4. While speaking louder than normal into the microphone, adjust
the ALC POT on the rear
panel thru the access hole. Adjust for 1500
watts maximum output as indicated on an external peak reading
wattmeter. If an average reading wattmeter is used, adjust for
approximately 750 watts output on voice peaks.
5. On some of the late model transceivers this adjustment can be
adjusted in the CW position. On these models (with your output at 1500
watts) simply adjust for a slight drop in output.
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