Instruction manual

AL-800 Instruction Manual
10
volts and "20"=2000 volts. Do not operate the amplifier if the high voltage is over 2700 volts with
the amplifier on standby. See the
Transformer Connections
section on page 15 for
information on correcting excessive high voltage.
REF
:
The multimeter measures the antenna (or load) peak envelope reflected power in the REF
position. The full scale reflected power reading is 500 watts. This scale is marked every 10 watts
below 100 watts, and every 100 watts from 100 to 500 watts.
Note:
The SWR of the load can be measured when the
"MULTIMETER"
switch is in the REF
position by observing the different red SWR curves. The forward and reflected meter
pointers will cross each other on, or near, the correct SWR curve.
ALC
: The multimeter measures the output voltage of the ALC detector when in the ALC position.
The full scale ALC reading is 35 volts and is read directly from the ACL / HV scale. The meter
should flick upwards occasionally during normal ALC action. See
ALC Metering,
Controls, and Adjustments
operation on page 19 for more information.
ALC SET
:
The multimeter measures the approximate grid current that will produce ALC activity
when the meter switch is in the
"ALC SET"
position. One zero must be added to the reading on
the ACL / HV scale and the result divided by 2 for this function. For example, ALC action will
begin at approximately 75 mA of grid current (typically between 60 mA and 90 mA) when the
"ALC SET"
control is adjusted until the meter reads "15."
Wattmeter Circuit
The AL-800 wattmeter circuit uses an accurate directional coupler followed by a true peak detector
circuit. This circuit will accurately determine the true peak envelope power (PEP) of normal voice
waveforms. If the load SWR is high, the true power reading can be obtained by subtracting the
reflected power from the forward power reading.
Peak Envelope Power vs. Average Power
Peak envelope power (PEP) is often misunderstood. PEP is not associated with the sine wave or
root-mean-square (RMS) power, and it has no fixed ratio to average power. There are no formulas
that allow accurate conversions between average and peak voice waveform power.
PEP is the power at the crest (highest point) of the RF waveform. On SSB, the average power can
vary from a few percent of the PEP to over fifty percent of the PEP. Generally, the PEP on SSB is
two to five times greater than the average power. On CW or other constant amplitude modes (such
as FM or RTTY), the PEP is always equal to the average power.
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