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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
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.
Product is in production
More Info: http://www.mfjenterprises.com
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00253.9
KJ4NWZ Rating: 2014-06-26
Better review Time Owned: more than 12 months.
In my last review of the MFJ-931 i gave the unit a 4/5 rating. I'd like to upgrade it to a 5/5. I've had the unit for more than a year, I now know EXACTLY how to use it and my rain gutter antenna is most happy with it. They have the perfect marriage.
VE3TKB Rating: 2013-12-27
Works just fine Time Owned: 0 to 3 months.
I live on the second floor of a four story apartment building. I use a balcony mounted MFJ-1622. I am a long way from a decent ground so today when my MFJ-931 arrived I hooked it up to my TS-520S and ran a 15 foot wire to my baseboard water heated radiator. The difference was significant. My RFI is all gone and I get a little quieter receive signal. I only run 10 watts here as I am mainly on JT65-HF and I must say it works fine on all bands I use from 10-40 meters. If your shack is far away from a good RF ground I would highly recommend trying this. The construction of the unit is sturdy and I popped the lid and noticed no flaws or cold solder joints. A good addition for the Cliff Dwelling crowd :)
KL7T Rating: 2013-01-24
no problems Time Owned: 0 to 3 months.
Received this product yesterday. I use an indoor loop antenna in my bedroom, no ground connection during the winter. I took the cover off and found everything to be perfect. I hooked it up in counterpoise mode with two wires on the floor. I could adjust the inductance and capacitance to maximize ground current. I am giving it a good rating because it worked exactly as expected.

Has it increased my signal output? I don't think so.
In the summer I do run a 35 foot ground wire out the door to a copper rod driven into the ground. (my bed room happens to have a door to the
outside). This artificial ground is supposed to reduce the impact of the length of the ground wire in this situation. Also in the summer I use the MFJ-1788 mag loop antenna.
KD1AM Rating: 2012-09-09
Fine performance and construction quality Time Owned: 0 to 3 months.
We just set up an IC-7200 in our EOC and, as the radio room is on the second floor, didn't get a very good RF ground, weren't near an earth ground, had RFI problems on TX audio, etc., etc..

With some trepidation (based on the quality problems reported here) I picked up a new MFJ-931 at HRO in Salem. The first thing I noted is that the unit no longer looks like the photo above; it's been slightly redesigned in that the inductance knob is mounted higher on the front panel.

Opening up the cabinet reveals a very nicely built product. All solder joints are properly flowed, wire and cable routing is tidy, and leads from the inductance wafer switch to the large coil are neatly arranged. Clearly the maker has spent some time cleaning up earlier issues.

There are two ways to hook up the device, either tuning a single (or multiple) counterpoise wires, or tuning a long-run ground wire from the radio chassis, in series through the MFJ-931, to a termination at an earth ground. We used that second mode with good success on 75/80 and 40 for both digital and voice modes. Receiving stations reported much improvement in audio and the digital throughput was higher.

Later I tried the device at the home station. There I already have plenty of solid DC and RF grounding so I laid several counterpoise wires of differing lengths out on the house floor and connected to the MFJ-931's output post. The device chassis was connected to the station's DC ground buss. Once again I found that digital throughput was higher once the counterpoises were tuned with the MFJ-931.

This has been a useful addition to my kit and my next test will be with an NVIS antenna system on Field Day. It's a bit of a specialized item but my guess is that many stations could benefit from improved counterpoise tuning.

de N1HWI
N6JPA Rating: 2011-03-12
I sent mine back Time Owned: 0 to 3 months.
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.
WA7KGX Rating: 2010-09-08
Check b4 Buy Time Owned: 0 to 3 months.
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.
KH6DC Rating: 2010-08-05
Now That You've Mentioned It Time Owned: more than 12 months.
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.
W4IW Rating: 2010-08-05
It's This or No HF Time Owned: 0 to 3 months.
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.
W4PGM Rating: 2010-05-16
Works, but repairs needed before it did Time Owned: 0 to 3 months.
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.
FORMER_K2QI Rating: 2009-07-25
Good product at a reasonable price Time Owned: 0 to 3 months.
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.