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Reviews For: MFJ-834 RF Coaxial Ammeter

Category: SWR & Wattmeters & Dummy Loads

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Review Summary For : MFJ-834 RF Coaxial Ammeter
Reviews: 4MSRP: $79.99
A calibrated in-line coaxial HF RF Ammeter with full scale ranges of 0.3, 1.0, and 3.0 amperes
Product is in production
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# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
N1BEC Rating: 2018-05-13
Not a bad design, but meter really needed 2 scales. Time Owned: 0 to 3 months.
I had the opportunity to evaluate an 834 as part of an estate sale.
The first issue I discovered was that the unit was reading very low, so I'm wondering if it was sent out calibrated as an 834H by accident (or poor QC).
Once properly calibrated on the 1 Amp scale, it worked fine on the 3 Amp scale as well. I didn't check it on the lowest setting (.3 Amps), as that's about 4.5 watts, and I don't have a power attenuator handy at the moment.
I liked the unit except for its odd scale of 0-100: This is fine for the 1 Amp setting, but doesn't work out so well for the .3 or 3 Amp scales.
What MFJ should have done was have two scales: One from 0-1, and another next to it from 0-3, so it would be direct reading on the .3/3 Amp scales as well.
Because of this, I'm moving it along.
Still, it's an intriguing piece of test equipment, and has a lot of uses.
Like the 269 antenna analyzer, I think it's one of MFJ's better ideas, just not executed as well as it could have been.
K6SDW Rating: 2014-11-05
Quality control sucks! Time Owned: 0 to 3 months.
I bought the MFH-834H (the high-powered unit) and right out of the box it would not work!!!!

Yup, you all guessed it, two cold solder joints. Even before I removed the screws to the cabinet, I turned on the soldering iron.....yup, two joints to the meter weren't soldered!!!

Come ON MFJ, really -- Dr. Jue, you could have a world-class company if you guys paid attention to quality control....

Where else can I buy an RF Ammeter for less than $100 that actually works?

Anyway, the ammeter works FB, but it just irked me that MFJ has such poor QC. I've bought many MFJ products from them and all work as advertised, but some need repairs when they arrive brand new.

Cheers All
K4WYS Rating: 2010-08-06
LED Dial Illumination Time Owned: more than 12 months.
I have been using the MFJ-834H antenna current meter for a little over a year monitoring the power to my wire antennas. Recently I noticed that the dial lamp was not working. After some investigation I found that the lamp was built internal to the meter, a long incandescent
bulb mounted in the plastic meter frame.
After a review of the use of LED's for dial lamp replacements, I followed a lead from AD5X, Phil and choose a pair of white LED's # 83 from All Electronics, with a 510 ohm current limiting resistor.
I used "Super Glue" to affix the LED's to the top of the meter inside the cabinet, relocated the supply wires to the new LED's. The light shines down onto the dial with a nice blue tint which illuminates the whole meter movement. Power consumption looks like 0.18 watts, that should provide a long life dial illumination.
AE5KA Rating: 2009-01-27
Appears to do what it says Time Owned: 0 to 3 months.
I purchased this after reading a recent QST article (Feb 2009) discussing the virtues of using an RF ammeter in the Ham Shack. It is a fairly simple device that passes the RF signal through a toroid transformer, and loads, detects, scales, and meters the toroid's current output at the secondary. Appearance and construction are typical of the MFJ product line. Internal construction and soldering appears to be workmanlike. In use, I found that though I had ordered the low-power MFJ-834, and the cabinet markings indicated it was such, the meter was reading an order of magnitude lower on all ranges than it should have. As it turns out, it had been calibrated as the high power model, the MFJ-834H. A call to MFJ technical support revealed that all that was needed was to adjust the internal calibration trim pot to get proper readings and turn it back into the MFJ-834 model. This was easy to do by noting the reading on the 0.3 amp scale, then adjusting the trim pot to give that same meter deflection on the 3 amp scale. The range to range linearity is OK, within 5% on my sample. I don't have a way to confirm its absolute accuracy, so am unable to comment on that. Its greatest value is probably in giving relative current readings during station/antenna adjustments. Is it something I really needed? I'm not yet sure, but I hope to be able to learn a thing or two with it.