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Introduction
Congratulations on purchasing the MFJ-854 RF-Current Meter. The MFJ-854 is
designed for measuring current distribution on antenna elements and radials, and for
checking common-mode current levels on coaxial feedlines and grounds. It also works
well for tracking down RFI-causing current on household wiring and cables. Here are
some important features we think you'll like:
Wide Range: Measures RF current from as little as 1 mA to 3 Amps in six ranges.
Full HF Coverage: Accurate from 1 MHz to 30 MHz and beyond.
Low Interaction: Sense coil has minimal effect on circuits under test.
Large Cable Capacity: Accepts cables up to approximately 1/2" in diameter.
Accurate: Diode-compensated Op-Amp delivers improved meter linearity.
Rugged: Built to last with a sturdy all-aluminum case and G-10 pc board.
Battery Saver: Press-to-test power circuit turns unit off automatically after 15 seconds.
Long Battery Life: Meter draws 3-mA, battery's service life approaches shelf life.
Handheld Size: Weighs 11 ounces, only 2.3" x 1.6" x 6.5" (including sense coil).
Controls and Locations
1
Cable
2
100mA 300mA
3
1A
30mA
<30mA
3A
Adj
Ampres
Power
6
On
4
5
9-V
MFJ-854
1. Sense Coil: Clamps onto conductor under test, accepts diameters to around 1/2" .
2. Meter: Calibrated scale indicates readings in mA or Amps.
3. Range: Selects from six measurement ranges.
4. Sensitivity: Works on <30 mA range, adjusts gain for low-level measurements.
5. Power On: Momentary switch applies power, activates 15-second power-off delay.
6. Battery Clip: Accepts any standard 9-V flat-pack battery.
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Summary of Contents for MFJ MFJ-854
- Page 1 Introduction Congratulations on purchasing the MFJ-854 RF-Current Meter. The MFJ-854 is designed for measuring current distribution on antenna elements and radials, and for checking common-mode current levels on coaxial feedlines and grounds. It also works well for tracking down RFI-causing current on household wiring and cables. Here are some important features we think you'll like: Wide Range: Measures RF current from as little as 1 mA to 3 Amps in six ranges.
- Page 2 Battery Installation and Replacement: Use any fresh 9-volt flat-pack type battery (not supplied). To install, remove screw from each side of case and gently separate two halves. Install 9-volt battery on snap clip, then slip into retainer (see previous drawing). To prevent damage from battery leakage, always remove battery when storing meter for prolonged periods.
- Page 3 Range: The Range switch selects between five calibrated scales (from 30 mA to 3 Amps). The sixth range is uncalibrated and tied to the unit's Sensitivity control. 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).
- Page 4 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 (see In Case of Difficulty).
- Page 5 Schematic Parts List...
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