AL-800H Instruction Manual
15
"PLATE" Control
The
"PLATE"
control adjusts the output tank circuit to resonance. This control should
always
be adjusted
for maximum RF output power. Maximum RF output power normally occurs simultaneously with
maximum grid current and very close to the plate-current "dip."
"LOAD" Control
This control adjusts the coupling of the amplifier to the antenna. This adjustment is necessary to insure
optimum coupling to the load as the SWR of the load, the operating frequency, or the power level is
changed. Advancing the
"LOAD"
control clockwise increases the RF power output capability and the
linearity of the amplifier. Advancing the
"LOAD"
control also
decreases
the grid current and
increases
the plate current for a given amount of drive.
The efficiency of the amplifier and the grid current decrease if the
"LOAD"
control is rotated beyond the
point of maximum output. The linearity, however, will increase. The proper position for this control is
slightly
clockwise from the setting that produces maximum output with full drive-power applied. Never
use this control to adjust the output power.
CAUTION:
Failure to adjust the loading control properly can result in excessive tank circuit
voltages and damage to components.
The
"PLATE"
control should always be checked after the
"LOAD"
control is adjusted by more than one
number. For example, if the
"LOAD"
is advanced from 1-1/2 to 2-3/4, the
"PLATE"
should be re-tuned.
If the
"LOAD"
is touched up a small amount, the
"PLATE"
setting will not usually require re-adjustment.
ALC Metering, Controls, and Adjustments
ALC Metering Functions
The
"MULTIMETER"
switch in the AL-800H has two positions that indicate the functioning of the ALC
circuit. These positions are as follows:
ALC
...
In this position the multimeter measures the output voltage of the ALC detector. The full scale
reading of the ALC detector voltage is 35 volts. It is read directly from the
"ACL / HV"
scale of the
multimeter. The multimeter will indicate the maximum value of ALC voltage available from the internal
ALC circuit. The meter should flick upwards occasionally during normal ALC action in this position.
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
"ACL / HV"
scale and the result divided by 2 for
this function.
For example: If the meter reads 15, add one zero (150) and divide by 2 (75). In this example ALC action
will begin at
approximately
75 mA of grid current.
