MFJ-817C Deluxe VHF/UHF True Peak Reading SWR/Wattmeter
Instruction Manual
3
Calibration
The MFJ-817C has been calibrated at the factory. If it should ever need to be
recalibrated, then follow this procedure:
Equipment Needed
1. Transmitter capable of supplying enough power to obtain ½ to full-scale reading
at 144/220/440 MHz.
2. 50-ohm dummy load that is capable of handling full transmitter output power and
has better than a 1.15:1 SWR at 144/220/440 MHz.
3. Power meter of know accuracy. The calibration will only be as good as the
standard reference meter.
4. 50-ohm cables capable of handling the power. RG-58/u is recommended. DO
NOT USE RG-59 or RG-11.
Meter Calibration
1. Refer to
Figure 1
for the Test Setup and refer to the PCB layout in
Figure 2
for
trim pot location.
2. Remove the top of the MFJ-817C.
3. Connect the Test Setup equipment as shown in
Figure 1
. Use a 50-ohm dummy
load for the antenna. Set the Transmitter to the 144/220/440 MHz in the
VHF/UHF band.
4. With the
300/30 Watts
button pushed
in
for the 300 Watt scale, Transmit 100
Watts as indicated on the reference meter. Adjust the HI FWD trim pot to set the
forward power scale to 100 Watts.
5. With the
300/30 Watts
button pushed
out
for the 30 Watt scale, Transmit 10
Watts as indicated on the reference meter. Adjust the LO FWD trim pot to set the
forward power scale to 10 Watts.
6. To set the reflected power, interchange the TRANSMITTER and ANTENNA
coax cables so that the transmitter is connected to the ANTENNA connector and
the dummy load is connected to the TRANSMITTER connector.
7. With the
300/30 Watts
button pushed
in
for the 60 Watt reflected scale, Transmit
10 Watts as indicated on the reference meter. Adjust the HI REF trim pot to set
the reflected power scale to 10 Watts.