AMERITRON AL-572, Instruction Manual

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Ameritron AL-572 Instruction Manual
19
ALC SET
In this position the multimeter measures the approximate grid current that will produce ALC
activity. One zero must be added to the reading on the ALC/ HV scale for this function. For
example: If the meter reads 15, add one zero (150). In this example ALC action will begin at
approximately 150 mA of grid current.
ALC Controls
The position of the "ALC SET" control determines the grid current value that will begin to
produce ALC voltage. Rotating the "ALC SET" control counter-clockwise
reduces the
maximum grid current obtainable and the available RF power output. Rotating the "ALC SET"
control clockwise
increases
the maximum grid current level.
The approximate grid current available before ALC action begins can be determined by placing
the "MULTIMETER" switch in the "ALC SET" (far clockwise) position. The "ALC SET"
control should normally be adjusted to produce a multimeter reading of 12 to 18 volts with the
"MULTIMETER" switch in the "ALC SET" position. This will allow a maximum grid current
of approximately 120 to 180 mA.
ALC Adjustments
SSB Operation
During SSB operation two adjustments affect the ALC and the sound of the signal. One is the
exciter's
microphone gain (or RF output level) adjustment. It will control the "fullness" of the
ALC and the average output power. It will have very little effect on the peak output power,
however. The fullness of ALC action is indicated by the meter reading in the multimeter ALC
position. More exciter audio gain or power output will drive the amplifier's ALC circuit harder,
and produce a more constant meter reading. This produces RF compression that increases the
"talk power" without increasing signal bandwidth or distortion.
Note: Audio background noise will increase while using heavy ALC levels on SSB.
Objectionable background noise levels may occur while using heavy amounts of
ALC, especially if the heavy ALC levels are used in conjunction with other speech
processing. In these situations, operating in a quiet room and "close talking" the
microphone will minimize objectionable background noise.
The amplifier's "ALC SET" control determines the level of grid current that produces ALC
activity. The maximum power output level. This amplifier has the best linearity when the "ALC
SET" control is adjusted to limit the peak grid current to 150 mA or lower. This adjustment must
be made with a carrier or single tone signal. When the "ALC SET" control is properly adjusted,
it will be impossible to exceed 150 mA of grid current with any tuning or drive adjustment.
CW Operation
During CW operation the "ALC SET" control voltage should be adjusted just high enough
(clockwise) to allow the desired output power to be reached. The "ALC SET" control should
never be adjusted to the point where the grid current can exceed 200 mA under any tuning or
drive adjustment condition. During proper CW ALC operation, the exciter drive level control