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Reviews For: MFJ-931 Artificial RF Ground

Category: Specialized Amateur Communication Products

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Review Summary For : MFJ-931 Artificial RF Ground
Reviews: 25MSRP: 89.95
Resonates a random length wire counterpoise and produces a tuned artificial RF ground or places a far away RF ground at the station equipment by tuning out ground lead reactance.
Product is in production
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# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
LB6BG Rating: 2020-04-30
Does the job perfectly Time Owned: more than 12 months.
I have owned the MFJ-931 for some years, but never found any use for it. However, when I extended my inv vee with open feeder from 2x14m to 2x17 meter, I got an issue with distorted modulation on SSB, and some QSO-partners told me that i might have RF on my equipment. Note that I have no possibility at all to get a ground in my shack under the roof. So I decided to try the MFJ-931 again. As a ground line, I taped a 9 m long wire along the floor. After tunig the groundwire on 80, 60 and 40m, the RF-issue was gone and my modulation was ok. I found no issues on the construction quality of the MFJ-931 :-)
BURGERLOVER65 Rating: 2018-08-03
Not dependable Time Owned: 6 to 12 months.
I purchased this to try and prevent tvi for my neighbors. Trouble is on one day it shows considerable ground current. The next day I go back to the same antenna and the same band and it shows no ground current at any settings. Doesn't make sense. At one point I got out the soldering iron and touched up all the solder beads. No changes. So I don't know what is going on with this thing. Either it works intermittently or the readings are false. Its always a risk dealing with MFJ.

Earlier 5-star review posted by BURGERLOVER65 on 2018-02-16

This MFJ 931 does so much for my station my operating would be seriously limited without it. It eliminates most rf bite from not having a natural rf ground. It also fights interference to my neighbors TV's. It allows me to use a rooftop vertical antenna without four radicals. I am doing well at the ARRL CW DX contest because of this. It also works well with my multi band end fed antenna improving performance measurably. This artificial ground is the most important equipment in my shack for improving DX performance by giving a repeatable, predictable counterpoise I otherwise would not have. Poor operating conditions are no more for me due to a poor antenna system.
W5RHR Rating: 2018-01-22
needed repair first Time Owned: 0 to 3 months.
I have RF in my "work qth" shack since I have no easy way to establish an earth ground.

After reading the reviews I decided to give it a try, and right out of the box didn't work.Touched up some solder joints and wiring issues on the switch/coil, and the biggest issue was the ground pad on the circuit board was not making contact through the mounting screws to the chassis.

Rather than send it off forever to MFJ I effected the repairs myself

After finishing all the repairs and firing it up, it started working and removed my RFI.
W6UXB Rating: 2017-11-20
Better after use Time Owned: 0 to 3 months.
I hope eHam will let me submit another review, after using this awhile I have to say I give it a 5, I have been using it with a PAR EF QUAD end fed wire for 40-20-15-10 and I used to get through to most stations I could here but they would say 5-5 can just hear you, after using this I am getting 5-7 or 5-9 good signal, I have made more contacts after installing this I only have a 4 foot copper rod with about 12 feet of copper wire attached, great little box!
M0XFL Rating: 2017-09-21
Great - Works as expected Time Owned: 3 to 6 months.
My shack is on the third floor and suffered from earthing issues even with a thick copper braid connected to ground outside the house.
I added the MFJ-931 between the earth and my radio equipment, this gave an immediate reduction to stray RF on 40m. I also added a counterpoise which offers the same improvements on 20m. Therefore I am happy. My 931 unit is well made and works as it should. Great!
AC9KJ Rating: 2016-09-05
Worked for a few days, then quit Time Owned: 0 to 3 months.
Worked fine for six days - then suddenly stopped working today. I had bought it through Gigaparts because I've had bad experiences with MFJ's service department in the past.
KK6ZTI Rating: 2016-03-03
Huge Improvement For 2nd Floor Station Time Owned: 0 to 3 months.
I'm a new HAM whose only had this product for 1 day at the time of this posting, so I'll probably return with a followup review in a few months. Note this is for a latest model 931 with a 2013 build date. Apparently they aren't selling too well considering it's 2016.

I have a CHA-250B, live in a densely populated area and have a 2nd floor station.

My RX has been "ok" but my TX was horrible. Most stations I could hear wouldn't hear me, even many within favorable propagation conditions between us.

I setup the MFJ-931 with my FT-450D transceiver ground and a 70' counterpoise wire. I'm consistently getting subtle to moderate RX improvements and giant TX improvements on 80m & 40m since doing so. Basically it seems I can now talk to whomever I hear (given propagation), even to local stations which should be a little challenging on a CHA_250B. Will be seeing how this fares on 20m soon but anticipating similar results.

The catch is a 70' counterpoise wire looks pretty silly laid around my small station room. I'm hopeful shorter wires will work as well but am a little concerned about it, at least on 80m.

Build quality seems to be an issue with many. Fortunately I haven't noticed any circuit connection issues however my capacitance knob has no stop point, which if intentional is a big design flaw in my opinion.

My next endeavor will be installing an antenna counterpoise, which should take TX up another notch.

Why do I keep bolstering an expensive "dummy load" antenna? Beyond it's simple installation and (kind-of) low profile, I love reaching out thousands of miles, night after night.
MI0HPE Rating: 2015-07-31
Looks promising Time Owned: 0 to 3 months.
I just acquired this recently, My shack is three floors up so no usable rf ground from the stake in the back yard. Results so far are very promising, needs more experimentation with counterpoises etc.
One of the nicest things about this is that the simplest solution can also be the best one.
WI7B Rating: 2015-03-28
The Other Half of Your Antenna Time Owned: 0 to 3 months.

I have a #26 stealth long wire antenna strung from my 2nd floor condo. Without the MFJ-931 resonating my balcony counterpoise, I would not be able to transmit efficiently. Your counterpoise is the other half of your long wire antenna. The RF current flowing through it is a match to the RF current following through your antenna. More is better here. The MFJ-931 allows that to happen. In addition, there are no complaints of RFI from neighbors. They don't even know I'm transmitting 300W and all this for $100. If I could give this 6-7 stars, I would. Best improvement for my station, ever!
VA2PBJ Rating: 2014-07-09
Great Product Time Owned: 0 to 3 months.
It's one of this things that is indisposable when you need at and no big deal when you don't.

I bought it, but my longwire and 20m vertical were taken down for tree removal. Time to put them back up to really get this thing working.

It arrived and I did the usual inside inspection. All was good as every MFJ product I owned has been.

I hooked mine up to a 2 foot pipe (electrical conduit) I pounded in the ground. The earth is rocky here and it has not proven to be a great ground. It is what it is.

The only working antenna I have is a 40m ocf. No deflection on the current meter for 40 and above, but from a balanced antenna it was no surprise. Not so on 80m. For the first time I was able to tune it down to 2:1. I guess when you go out of band, it kicks in.

Time to put up the other antennas and get on the air.

It's something I've thought about for a while and I am glad I took the plunge. If I was not in a metal sided house, I might have considered throwing a wire across the floor and tuning that.

It does have two shortcomings though. The current meter should be more sensitive and I can't figure out an omission of a light for the meter.