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Reviews Categories | Antenna Tuners/Matching Networks | MFJ-936B Help

Reviews Summary for MFJ-936B
MFJ-936B Reviews: 12 Average rating: 4.3/5 MSRP: $259.95
Description: The MFJ-936B is a specialised small wire loop tuner for portable/home use. It has built-in SWR and RF antenna current meters for tuning. It turns virtually any wire loop into a high efficiency transmitting magnetic loop antenna. Depending on its length, and this can be 5ft, 10ft or longer, it is possible to cover two or more amateur bands. You can operate up to 150W, no ground, radials or counterpoises required. The wire can even be simply draped around a bookcase. The MFJ-936B has a carry handle built into the side. There is a detachable PVC mount that bolts onto the top of the case. Into this can be placed a PVC frame cross (MFJ-57) for mounting a 20-15m or MFJ-58 for mounting a 17-10m antenna, alternatively you can use insulated wire such as PVC coated multristranded copper wire to form an antenna. You can tune any shape loop - circle, square rectangle, any odd shape. A quarter wavelength wire shaped as a circle is the most efficient though. A 10ft wire formed into a loop operates 20-15m, 5ft for 17-10m, 24ft for 30-40m.
Product is in production.
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G4VZV Rating: 5/5 Jan 15, 2018 15:37 Send this review to a friend
Excellent  Time owned: more than 12 months
Excellent device where you cannot use outside antennas, or for portable use. It is a magnetic loop in all but name. What you're buying here is the tuning system for a loop and you can indeed use any conductive material as the loop. Use wire, use copper tubing ,aluminium strips the heavier duty the better, I've used this device at home and portable and used wire to 1 inch diameter copper tubing. It works like a dream low noise, simple , so so easy to use and tune up the loop. Results: Amazing ....i mean amazing for example the 20mts band loop of total length 7 feet produces QSO's all over Europe and sometimes much further. Lookat my QRZ page or DXNews page under my call for images and log book recorded QSO's (G4VZV) It's a joy to use ....MFJ this is a winner !!!!
SP9NLI Rating: 5/5 Jan 7, 2018 12:44 Send this review to a friend
Great portable solution  Time owned: 0 to 3 months
I've been messing around with this tuner for two months now and find it really excellent.
At first I feared that some of the comments here were right saying that the SWR-meter was useless showing huge reflected current when the antenna is matched.
Actually, it is not the case, when the tuner shows a mismatch, it means that the matching capacitor needs adjusting.
Once I figured out how to bring do reflected needle down to zero with each and every loop I put on it, the whole tuning process is fast and easy.
The SWR and power meter seems perfectly calibrated, so I give it 5 stars despite finding one of the matching capacitor's blades slightly bent and short-circuiting the signal at some point.
A great solution for portable QRP operation.
AE7TO Rating: 5/5 Jul 21, 2016 18:40 Send this review to a friend
Great Travel Antenna  Time owned: more than 12 months
I bought the MFJ-936B a couple of years ago so I'd have something better to do than watching TV when in the hotel on business trips . The first thing I learned is that this thing is tricky to tune, as many others have said. And it must be re-tuned if you change frequency by more than about 10 KHz. Eventually I learned how to consistently get SWR below 1.5 by using an antenna analyzer. After an initial "earball" tune for max static on the radio, I VERY gradually home in on low SWR by alternately adjusting the Tune and Match knobs while watching the analyzer (overshooting each knob slightly past the lowest SWR) until the match is acceptable. I have also attempted to use MFJ's "manual screwdriver" (with a telescoping whip) as a travel antenna. That setup works well outdoors, and is easier to tune. But it isn't practical indoors, where the ceiling interferes with extending the whip. My 13 foot circumference loop, on the other hand, works indoors and out. So I'm back to using the loop (13 feet of soft copper 3/8" OD tubing that I can coil into a suitcase). By the way, I don't use the Current meter for tuning because the analyzer works fine. But the cross-needle SWR meter is very handy. Saves me from packing a separate meter.
K1OYQ Rating: 4/5 Feb 22, 2016 06:02 Send this review to a friend
It works very well!  Time owned: 0 to 3 months
I picked one of these up used and experimented with it for about a week. I started out with a loop of #12 wire and found that to be just about useless (as expected). I then tried RG-58 coax and noticed a big improvement right away. Then I tried low loss RG-8 coax (shield only) and noticed a significant improvement. I haven't tried 1/2 inch copper tubing yet, but I'm sure that will be even better then the aluminum shield on the RG-8. I made three loops out of the RG-8 (13ft, 9ft, and 4ft). All of these loops worked well and I made CW and SSB contacts on each using 5 to 50 watts. The true test came during the ARRL CW DX contest and I used the 13ft loop on 20M. I worked most of the EU and a lot of SA stations with 5 watts with an FT-817. My next test will be an A/B comparison of the loops vs Buddipole antenna. The downside of this tuner is that the SWR meter is about useless. As far as I can tell it does not provide any useful information. In fact the SWR meter shows huge reflected current when the antenna is tuned properly (max current on the MFJ current meter and low SWR on the rig). I'll have to research this a little more (meter connected backwards?). That is why I gave it a 4. I would recommend the MFJ-935B vice the 936B. I do not recommend using the top 3/4" PVC support on the 936B for antenna support for the 13ft or larger loop due to the stress from the weight. It is ok for the 9ft or less loops. The loops exhibit the same directivity as a dipole which can be useful during operations. This antenna tuner has now become a part of my Go-Kit of emergency and portable antennas.
AH6OY Rating: 5/5 May 5, 2015 14:47 Send this review to a friend
Works  Time owned: more than 12 months
While travelling if you are going to stay in a tall hotel room this tuner works fantastic. G2SZU / KH6ZU used my tuner downtown Waikiki and worked a chum in England 579. This was from the long path side of the building. I think a combination of height and buildings magnetic field help setup good working conditions. Keith was arranging the 13' wire loop strung horizontally so that a portion was 1" off from the metal balcony railing. I also have a feeling since current regulations for safety concerning high rise balcony railing require the railings to be welded to the concretes rebar that it gives the antenna a great shot at tying into the whole buildings height to help radiate signals and receive better.

So pretty much the loop plays better at height oriented horizontally. Rigging low and vertical you have sharp nulls and don't get out as good. Bought the tuner to fight noise and have for a portable backup. Works fantastic for a loaner to visiting friends.

Caution is the unit is not sturdy concerning the rear connector lugs. Twisting hard on the wing nuts can torque the inside components loosening and bending components. My case causing this malfunction was using copper waterline tubing unsupported and it flopped from side to side. Damage was repairable but the unit could be improved by making it with insulated standoffs instead of connections just going through gaps in the rear of the case. The tuner can give an RF bite if you touch the case. It didn't help matters that when receiving the tuner new it had a loose screw floating around inside I had to install. Like they say, you get what you pay for and that's pretty much a crap shoot.
AA9G Rating: 5/5 Feb 18, 2015 11:31 Send this review to a friend
Great for what it is.   Time owned: 6 to 12 months
The first thing you have to realize about this product is that it is not a 3 el yagi at 70 feet. If you keep your expectations in line with the fact that this thing tunes a few feet of wire while sitting on a chair in the spare bedroom all is well.
The only thing I don't like is it is quite inconvenient to change bands. For that reason I stopped using it for SSB and focused solely on 20m JT65. I tuned it once and there it stays.
In ten months of very sporadic operation I have 158 contacts (if you made no contacts with this thing, I'm sorry but you did something wrong.)

I've worked almost every entity in the western hemisphere, down to DP1POL in Antarctica, 8,600 miles from my QTH. France, UK, Spain, Portugal, Russia, Ukraine and Asiatic Russia are in the log. It is not convenient to use at all but then it really cannot be. But if you are not a band hopper, can tune it for one spot and be content to work that for a period of time, you can do well with this setup.
KQ6BC Rating: 5/5 May 11, 2014 12:12 Send this review to a friend
A good compromise  Time owned: more than 12 months
First off, although it seems kind of expensive, it's not really out of line. Apart from a few feet of 'any' wire and feed coax it is a complete, portable antenna system that is good to go. You could pay more for a multi-band vertical and get less hardware. You could throw up a wire dipole for a lot less but it's tough to do inside a residence. The build quality is pretty solid and the aluminum case fit and finish is more solid than most MFJ items. The control knobs feel smooth in operation and the meters are standard MFJ.
In operation it does a great job as far as a receiving antenna. It receives both signals and in-band noise, which is what you would expect. With a fine touch of the hand and an appropriate length wire loop you can zero into small segments of any covered band.
As a transmitting antenna system however, it can be pretty good or not so good. It does cover the bands. When things are right, you can work anyone you can hear. Although loops are not very efficient in general, the ability to tune the system makes up for quite a bit. The fly in the ointment is that of necessity the control box is sitting as the base of the loop. This is not so handy if you want to adjust the system to a particular small segment of a band as you are either going to do a bit of back and forth from the unit to your rig, or you are going to be operating too close to the loop RF field.
All in all, I can not see where MFJ could have done a better job, so I give it a 5 out of 5. The price is right. The build quality is right. The theory and execution is right. It is what it is, and I have had good success with mine.
WA8H Rating: 5/5 Jan 2, 2013 20:51 Send this review to a friend
It works  Time owned: 0 to 3 months
I held my breath and purchased one, along with the MFJ-59 kit. Well to my surprise it worked. I'm in a small farm town and in a valley. I have it indoors by the window. 20 Watts SSB and I've made several contacts. My signal is week but the audio was reported as clear. I'll play around with copper tubing and maybe up the power some. Tuning as reported is very sharp. But I'm back on the air after 7-1/2 years. Fit and finish was really good.
VE3GZB Rating: 0/5 Nov 24, 2012 11:58 Send this review to a friend
Mighty fine junk!  Time owned: more than 12 months
I wrote a recent review on my MFJ-396B which I've had for over a year now. Until today I have never succeeded in making a single contact, in having a single QSO with anybody in spite of appearance indicating that it was working.

Today I managed to finally have a very brief QSO, after which it started to make an arcing sound, then smoke. I was running it on my TS-820 at the time.

I opened it up and found insulation has melted on the wire which is used to wind the RF current transformer and as well, where the heavy lead from the capacitor comes out, it is painfully close to this same wiring which has melted.

Of course it is older than one year so the warranty is expired, forget the fact that until today I've not made one solitary contact with it.

Nice in concept, but atrocious in execution, the hardware used for assembly for this seems too "mickey mouse" to endure. I would not recommend this product to anyone unless they have a few hundred dollars to throw away.
VK2CCJ Rating: 4/5 Oct 16, 2012 20:35 Send this review to a friend
Very Surprising worked well but RF feedback a problem  Time owned: 3 to 6 months
I have had this unit for quite some time and really not had a lot of success using wire loops so the other day I cut some loops from 1.25inch copper strip and I got good results from inside (considering I am surrounded by steel fences a few feet away), on 20,15 and 10M so far.

Very sharp tuning so Hi Q which is good. I do get a lot of RF feedback with some transceivers and bands. I tried a RF choke but didn't seem to help.
If anyone has a suggestion ? My tranceivers are FT847 was very sensitive to RF close by, a JRC-JST245 less so and the little FT-817 almost immune.

Only using around 10W on JT65 into JA, US and Europe , a surprise was The Canary Islands. Would like to set it up in the open sometime.
73 Cliff
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