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 the lid over the cable, pressing down until latch clicks shut.

	Unlatch	Press
		Lift

Click!

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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 25.5 A. The chart below will help you estimate readings quickly:

		Range
Meter	3A	10A	30A
Reading	Actual Value (Amps)
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

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).

I = RP

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 MFJ853H 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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