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Reviews Categories | Specialized Amateur Communication Products | MFJ-931 Artificial RF Ground Help


Reviews Summary for MFJ-931 Artificial RF Ground
MFJ-931 Artificial RF Ground Reviews: 16 Average rating: 3.9/5 MSRP: $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
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K2QI Rating: 4/5 Jul 25, 2009 19:25 Send this review to a friend
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.
 
G0LGB Rating: 3/5 May 3, 2008 11:00 Send this review to a friend
Quality Issues ...again!  Time owned: 0 to 3 months
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!)
 
NE0P Rating: 5/5 Aug 27, 2004 11:04 Send this review to a friend
Worked great for me  Time owned: more than 12 months
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.
 
KB6G Rating: 4/5 Aug 27, 2004 03:28 Send this review to a friend
Works fine  Time owned: 0 to 3 months
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.
 
WP3HW Rating: 3/5 Aug 26, 2004 20:55 Send this review to a friend
Works, but QC issues  Time owned: more than 12 months
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.
 
KA3POY Rating: 3/5 Aug 9, 2002 18:38 Send this review to a friend
works, but so-so quality  Time owned: 0 to 3 months
Purchased one for my Dad who's shack is on the second floor of the house. Before adding the artificial ground, the rig was "hot" with rf, after installing and tuning, no more rf on the rig. However, if anybody else made a competing product I would avoid this one: one of the controls is extremely stiff to rotate, the other exhibits "hand capacitance" meaning that the meter reading changes when you touch the knob. This behavior was remarked upon in an ARRL product review many many years ago, and it is surprising that no effort was made to fix it.

73

N5IIT
 
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