AMERITRON AL-80B, Инструкция по эксплуатации

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AL-80B Instruction Manual
15
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
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 multimeter reading in the 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.