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Reviews For: MFJ-936B

Category: Antenna Tuners/Matching Networks

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Review Summary For : MFJ-936B
Reviews: 17MSRP: 259.95
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.
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# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
AA9G Rating: 2015-02-18
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: 2014-05-11
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: 2013-01-02
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: 2012-11-24
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: 2012-10-16
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
W2JAZ Rating: 2012-04-01
Much better than expected Time Owned: 3 to 6 months.
I bought this out of frustration and on a whim since even at a used price it wasn't cheap. I needed something to enable me to get on the air during those visits to my sister in law where I have absolutely nothing to do. I leave an ft-817 there along with signalink and bring a laptop. I tried everything, but during bad weather months found it impossible to get something set up outside and bring coax into the house. The mfj-936 is just what the doctor ordered and surprised me to no end, working dx on 20 meter cw fairly easily on 5 watts and from a ground floor bedroom. I have a small amp but haven't tried it or psk yet. My unit came with all of the premade loops and I've found that tuning is very sharp and sensitive. The loops don't always tune on the bands as advertised and depends on surroundings and height above ground. For example I could not get the loop designed for 17 meters to tune, so I cut my own to 9' 8" and it tuned just fine. All things considered I am very pleased and am as surprised as the other reviewer that this little gem hasn't caught on. I now enjoy my trips to visit my sister in law much more :)
N3LCW Rating: 2010-03-20
It works great! Time Owned: more than 12 months.
I've owned the MFJ-936B tuner for more than 2 years now. It really does work and it works very well.

The tuner is basically a magnetic loop antenna matching and tuning unit.

Using the tuner on the floor in a spare room and 13 ft wire loop for 20M I worked DX stations in Europe using 30W on PSK-31 with excellent signal reports. Not bad for an indoor antenna. The loop is much quieter than an indoor dipole or wire antenna but it still will get noise if you operate in a noisy environment (computer, etc). The high signal to noise ratio is excellent.

Use the largest loop as close to 1/4 wave as possible and the efficiency of the loop will be much better.

Also consider a two turn loop if you are restricted for space and want to operate the lower bands. Be sure to have a few inches space between the turns.

Another little secret: you can extend the low frequency range of the tuner using a larger loop or a two turn 32ft loop for example for 80M as long as you add a high voltage capacitor (doorknob cap, or HV air variable) in parallel with the loop terminals on the tuner. Try a 150pf capacitor for starters. A 1/8w loop at 80M is very effective especially if you can get the loop outside. Keep the loop vertical and you can operate with the tuner on a small table a few feet above the ground.

I built an X-Frame from two 10ft lengths of light duty 1" PVC (drinking water pipe),a cross coupler, notched the ends, and used it to support a 28ft length of #12 wire. I just set it vertically against a chair for support and connected to the tuner. I tuned if for 40M in the CW portion of the band and worked up and down the east coast and out to the west coast in one evening, only running 30W-40W out. (The tuner will handle 150W). If you can set the loop up on an outdoor deck so much the better.

I think this tuner is an MFJ winner and am surprised it hasn't caught on yet. This tuner will definitely help many amateurs caught with restrictive CCR's that can only use indoor antennas. For the higher bands set the tuner near a window.

The only negative: when I received the tuner the SWR meter was loose in the case. I reattached it and tightened the screws. The rest of the tuner is well built. I'm giving it a 5 since it works much better than anticipated.

Andrew N3LCW