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| Reviews Summary for MFJ-931 Artificial RF Ground |
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Reviews: 11
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Average rating: 3.5/5
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MSRP: $89.95
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Description: 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.
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Product is in production.
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More info: http://www.mfjenterprises.com
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W7KEW
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Rating: 0/5
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Mar 12, 2011 04:23
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I sent mine back
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Time owned: 0 to 3 months
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I don't know who made this unit for MFJ, but they did a horrible job. My unit did not work out of the box. I opened it up and I guess it was remanufactured. It had dozens of cold soldering joints, unconnected wires and the Coil connections were missing for a number of the switch positions. Avoid this product, I wasted $11 sending it back.
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WA7KGX
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Rating: 3/5
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Sep 8, 2010 14:12
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Check b4 Buy
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Time owned: 0 to 3 months
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BTW the catalog price is $109 now.
I bought one used. The switch was broken, fixed it with crazy glue.
The unit would not tune below 2.11 MHz. Not too good for 160 meters. I added a coil. Details on my blog.
MFJ did answer my call quickly and offered a replacement switch cheap (modulo S&H). Gotta give them points for answering the phone as not everyone does.
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KH6DC
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Rating: 5/5
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Aug 5, 2010 18:29
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Now That You've Mentioned It
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Time owned: more than 12 months
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Well I had this little doohickey for over 10 years and prior to that, got bit by the RF bug on my hands and lip from the microphone. Hooked up everything according to the instructions and no RF burns, no TVI except for recently. This is one MFJ product I forgot to check the interior and when I did, the cold solder joints fell off the connections producing intermmitent problems. No big deal, soldered 3 joints in fact resoldered all joints and everything works great. I've been and is still recommending this product to other hams with RF problems.
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W4IW
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Rating: 5/5
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Aug 5, 2010 16:45
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It's This or No HF
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Time owned: 0 to 3 months
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I think a lot of the previous ratings are outrageous. Is there another commercial product that does what this one does? I live in a 2nd floor apartment and my landlord graciously allowed me to put up a couple of stealth dipoles. I told him if the radio caused any problems I wouldn't transmit. Well, I had big problems with RF in my apartment and quit transmitting until I found a solution. The MFJ-931 is the solution and I can now enjoy ham radio in my apartment and not bother my neighbors. If it was just a kit it would be worth the money to me. Because it is the difference between HF operating or not, I would give it a 50 if I could. It works and it works well with a little fiddling.
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W4PGM
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Rating: 4/5
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May 16, 2010 13:44
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Works, but repairs needed before it did
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Time owned: 0 to 3 months
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The unit did not work out of the box. Same issues that preceded this review, bad solder, wires touching. Repaired the unit, reinstalled the unit and I was able to get a reading on the meter. Easy to use and seem to have made the difference for most of the issues. This is a 2nd floor installation to an 8' ground rod about 35' of wire.
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K2QI
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Rating: 4/5
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Jul 25, 2009 19:25
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Good product at a reasonable price
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Time owned: 0 to 3 months
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Bought an MFJ-931 because of a weird RF feedback problem that only happened when the linear was on. Installed it per MFJ's instructions, and all is now well. My only gripe is the case is a little warped that it wobbles on my table. Apart from that, everything works splendidly. Knobs turn smoothly also. I opened it up and checked the soldering, and that was FB too! All in all, a good product at a decent price... just wish that MFJ would get their act together with the cases.
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G0LGB
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Rating: 3/5
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May 3, 2008 11:00
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Quality Issues ...again!
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Time owned: 0 to 3 months
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As others have said the quality control & indeed the overall quality of components used is pretty poor.I bought mine a couple of weeks ago used, online.
I couldn't get a meter reading out of the thing on any band or power level, & the 12 way inductance selector was loose, so i opened it up & found some poor quality soldering inside & a couple of the wires from the selector to the coil were touching each other!(as it had not been opened up before i guess its last owner had little success with it?)
So i spent about half an hour re-soldering bad joints & straightening things up,(it really is very simple inside)put the lid back on & tuned my 817 to 40m & sent out a carrier...sure enough this time after turning the Inductance knob to J i got a full scale deflection & actually hasd to turn the Sens down just using 2.5W, this was with a roughly 15foot counterpoise, the best thing was the difference in received signals..almost 3 S-points higher than before so pretty pleased with its performance there!
After much chopping of wire I got it to tune on another couple of bands but so far 20m has defeated me...it seems to work with very random lengths of wire, the manual says "less than a quarter wave works best"....i wish they could be a bit more precise, I must have chopped up 25m of wire here!
If i can find a good quality 12 way selector i will replace that, the mfj one feels horrible & the quality is suspect there too.
Overall after repairs I am pleased with it, hopefully I'll hit the magic length of wire for counterpoise, just a big shame about MFj's poor quality control, if you buy one of these, used or new, take the lid off & check for obvious bad joints before you start to use it, 1 bad joint or touching wire makes these useless, but if like me you struggle to get a decent ground (i was just using the household copper pipes)then if you get one of these working it makes a big difference to reception & lowers vswr too...no bad thing if you are qrp..like me. (poetry!)
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NE0P
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Rating: 5/5
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Aug 27, 2004 11:04
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Worked great for me
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Time owned: more than 12 months
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I had one of these units for several years while I was in graduate school and had my shack set up in a second floor apartment with an indoor dipole and a hidden random wire outside. I ran a counterpoise around the baseboard in the bedroom, and hooked it to the artificial ground. I also used an MFJ 941E tuner, and did pretty good with this setup considering the antenna limitations. You could see the SWR change as you tuned the artificial ground. It also eliminated most of the RF problems I had. Of course with an indoor antenna you have alot of RF floating around.
I would recommend trying it to anyone who can't get a good ground due to station location and is having RF problems. Can't say for sure that it will work, as every situation is unique, but it worked for me.
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AE6RH
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Rating: 4/5
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Aug 27, 2004 03:28
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Works fine
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Time owned: 0 to 3 months
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Bought one after having phone EMI problems, and R.F. getting into microphone causing distortion. Shack is on 2nd floor. Had to play with different length counterpoise, and finally wound up with a fairly short wire ~ 15 feet, that works on 40, 20 & 17 meters. I also use an MFJ-949E Antenna Tuner with Carolina Windom 10-40 LP antenna. Combination of all 3 work quite well together. I consider the 931 the key to successful operation and less interference. I feel good grounding is important and have Radio and Artificial ground both connected directly to Antenna Tuner, which is my single point ground. Would definitely buy one again.
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WP3HW
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Rating: 3/5
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Aug 26, 2004 20:55
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Works, but QC issues
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Time owned: more than 12 months
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Purchased new. As purchased it was intermittent in operation. Opened the unit and observed poor soldering on some connections. Re-soldered and tightened everything. It worked OK after the "outpatient" surgery, and it still works like a charm in my second floor shack with no "real" grounding system. As noted previously by another reviewer, there remains a capacitance variation when a hand approaches it. The RF Ground Current reading on the meter changes somewhat when the hand attached to my body (my hand?) approaches the unit. My wife won't get near it.
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