MFJ MFJ-853H User Manual
INTRODUCTION
Congratulations on purchasing the MFJ-853H RF-Current Meter. The MFJ853H is designed for measuring RF current distribution on antenna elements
and radials, ground wires, and coax shields. Here are some important features
we think you'll like:
Range: Measures RF current in three ranges: 3A, 10A, and 30A.
Low Interaction: Sense coil has minimal effect on circuits under test.
Large Cable Capacity: Accepts cables up to approximately 1/2" in diameter.
Power: No power source needed.
Non-metallic case: Minimizes field disturbance for accurate reading.
Handheld Size: Light weight, only 2.25" x 1" x 3.75"
CONTROLS
1. Sense Coil: Clamps onto conductor under test, accepts diameters to around
1/2" .
2. Meter: Calibrated scale indicates readings in Amps.
3. Range: Selects from three measurement ranges.
OPERATING INSTRUCTIONS
Using the Sense Coil: The sense coil snaps over wires and cables, as shown
below. To unlatch, squeeze the nylon carrier between thumb and forefinger-applying opposing pressure. The coil's top section should move forward
slightly. With pressure applied, lift up to open. Position the wire or cable inside
the core opening. Close th e lid over the cable, pressing dow n until latch clicks
shut.
Unlatch
1 2
Lift
3
Press
Click!
Meter: The meter is scaled from 0 to 100. On the 10A range, move the
decimal point 1 place to the left (100 = 10 A). To convert meter readings made
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on the 3A and 30A ranges, multiply accordingly. For example, a reading of 85
on the 30A range equals 30 x .85, or 2 5.5 A. The chart below will help you
estimate readings quickly:
Range
3A 10A 30A Meter
Reading
10 0.3 1.0 3
20 0.6 2.0 6
30 0.9 3.0 9
40 1.2 4.0 12
50 1.5 5.0 15
60 1.8 6.0 18
70 2.1 7.0 21
80 2.4 8.0 24
90 2.7 9.0 27
100 3.0 10.0 30
Actual Value (Amps)
Range: The Range switch selects between three calibrated scales (from 3 to 30
Amps). To prevent meter pegging, begin checks on a high range and work
down. To estimate unknown current levels, use the formula below (I =
Unknown Current in Amps, P = Applied Power in Watts, and R = Load
Resistance in Ohms).
P
I
=
R
RF Hazard--Important Warnings:
1. RF-current measurements must be conducted with extreme caution. Physical
contact with conductors carrying even moderate RF-energy levels can result
in severe RF burns, or injury.
2. Avoid measuring RF current on conductors where high RF voltages may be
present (>500 Volts). Damage to your meter may result. Using the MFJ-
853H continuously for more than 1 minute on the 30 A range may
present these high RF voltages. When operating on the 30 A range,
we recommend operating at 10% duty cycle to prevent damage. .
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