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Page 17
) Set the transmitter to the TUNE or CW mode, tune
the transmitter, and watch the RF POWER METER
needle. If the meter needle does not move up-scale,
carefully increase the transmitter output. If the meter
needle does not move up-scale at 1/4 output, adjust
NULL trimmer C4 for a reading. If there still is not a
reading, refer to the "In Case of Difficulty" section of
this Manual.
) Adjust the transmitter output level until a reading of
approximately 25 is seen on the 200 scale of the RF
Load Wattmeter. Even if the meter reading is not this
high, proceed with the following steps.
Refer to Figure 2 and adjust NULL trimmer C4 on the
circuit board for the best null or greatest dip of the
meter needle. This reading should be at or near zero.
NOTE: Use only the alignment tool (nut starter) for
this adjustment.
( ) Increase the transmitter output to full power and
readjust NULL trimmer C4.
( ) Repeat the above step. Make this final adjustment
carefully
and
precisely.
The
accuracy
of
the
instrument depends on a well balanced bridge circuit.
Once this
is
set, be careful not to touch
NULL
trimmer C4 in the following steps.
( ) Place the FUNCTION switch to the 200 position. Do
not
disconnect
the
RF
Wattmeter
from
the
transmitter.
POWER METER CALIBRATION
Three calibration procedures are provided in this section.
Use only one of these procedures:
1. "Internal Calibration (40-Meter Only)."
2. "Calibration With External Wattmeter."
3. "Calibration With VTVM."
For maximum accuracy calibrate your RF Load Wattmeter
on the 40-meter band, even if it will be used on other bands.
If you cannot tune your transmitter (or transceiver) to the
40-meter
band,
you
can
use
one
of
the
other
two
procedures.
If possible, use 100 watts of power (not less than 50) for the
calibration steps. This will give the greatest meter accuracy.
Internal Calibration (40-Meter Only)
At this time, the Power Meter accurately indicates actual
power for only the conditions of the following steps. After
calibration,
the
unit
will
be
accurate
for
the
full
specification range.
1. ( ) Connect the CALIBRATE jumper on the circuit
board to the CAL pin.
2. ( ) Set the FUNCTION switch to 200.
3. ( ) Adjust the transmitter to read approximately 100
watts on the 200 watt scale.
4. ( ) Note the Power Meter reading.
5. ( ) Connect the CALIBRATE jumper to the NORM
pin and adjust POWER CALIBRATE control R6
with the alignment tool so the meter reads the same
as it read in the CAL position.
6. ( ) Repeat steps 1, 4, and 5 above until the meter
readings for both CAL and NORM connections are
the same.
7. ( ) Be sure the CALIBRATE jumper is on the NORM
pin.
This completes the calibration of your RF Load Wattmeter.
Proceed to the "Final Assembly" section of the Manual.
Calibration With External Wattmeter
( ) Connect the CALIBRATE jumper on the circuit board
to the NORM position.
( ) Set the FUNCTION switch to 200.
I I
Adjust the transmitter output to approximately 100
watts on any band.
Note the reading on the external Wattmeter and adjust
POWER CALIBRATE control R6 until both meter
readings are the same. Check the readings for accuracy
and proceed to the "Final Assembly" section of the
Manual.
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