MFJ-834H – HI PWR In-Line RF Ammeter 1-30 MHz


Like MFJ-834, but 3, 10, and 30 Amps high current ranges. Connect the MFJ-834 Coax In-Line RF Ammeter between your antenna and tuner/ transmitter/amplifier and measure antenna feedline current in 3 calibrated ranges.


Use it for tuning your antenna tuner/transmitter/amplifier for maximum radiated power, determining antenna feed point impedance, comparing antennas and tuners, troubleshooting and checking for changes. Tuning for maximum feedline current for any given antenna always gives maximum radiated power!

Any adjustment – transceiver or amplifier tuning/loading controls, antenna tuner settings, whatever – that increases feedline current improves power transfer and gives you a stronger radiated signal. Radiated power increases rapidly because power increases as the square of the current.

Minimum SWR does not always mean maximum radiated power – your tuner or lossy coax may be dissipating power – and you may not get peak output power even if your tuner or amplifier is properly tuned.

Use the MFJ-834 to determine the best antenna tuner settings and to compare various tuners. Calculate your antenna feed point impedance by dividing your applied power by the square of the feed point current.

Your antenna can change when you apply power – insulators break down, traps heat up, capacitors leak – and your feed point impedance may be drastically different from your SWR Analyzer measurements.

MFJ RF ammeters are rugged, read accurately over 1-30 MHz in three linear ranges (3, 1, 3 Amps) and barely perturb the antenna. Uses SO-239 connectors. Measures 6″ (W) x 3″ (H) x 4″ (D). Large 3-inch lighted meter. Use 12 VDC or 110 VAC with MFJ-1312D.

Additional information

Weight 0.8 kg