MFJ MFJ-817C Instruction Manual Download Page 3

MFJ-817C Deluxe VHF/UHF True Peak Reading SWR/Wattmeter 

Instruction Manual

 

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. 

 

Reviews: