MFJ-836 SWR/Wattmeter and RF Ammeter
Instruction Manual
6
RF Ammeter Calibration
1.
Refer to
Figure 1
for the Test Setup and refer to the PCB layout in
Figure 3
for trim pot location.
2.
Remove the top of the MFJ-836.
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 14 MHz in the 20-
meter band.
4.
Set the Current Range
selector to 1A. For meaningful results,
your wattmeter
must be accurate and the 50-ohm load free of significant reactance.
To test,
apply a 50-watt CW signal to the 50-ohm dummy load. You should observe a
full-scale reading of 1A (100 on the scale). If results vary significantly from
this reading, adjust trim pot R3 for the correct indication. Trim pot R3 is
located on the pc board below the sense coil.
Figure 3
: RF Ammeter PCB Layout and Trim Pot Location
IMPORTANT WARNING: Avoid direct physical contact with this device
when making measurements with power sources of over
5 Watts. RF burns or permanent injury may result from
contact with high RF voltages.
If your meter is out of calibration and you lack the equipment or skills to perform the
calibration procedure, you may return it to the MFJ factory for service.
R3
