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Reviews For: MFJ-935B

Category: Antenna Tuners/Matching Networks

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Review Summary For : MFJ-935B
Reviews: 13MSRP: 199
Description:
Small High Efficiency Loop Tuner
Product is in production
More Info: http://www.mfjenterprises.com/products.php?prodid=MFJ-935B
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
15134.4
KDMSKY59 Rating: 2012-02-08
compromise but it works Time Owned: 0 to 3 months.
The best thing about the MFJ 935B is it's quieter than most antennas as you probably already know. Here's the downsides: Whatever loop diameter you are using may tune one or two bands within it's range but not the third so you need to change the location of the tuner making tuneup unpredictable.
My 12 foot long 10 guage loop tunes 30M but not 20M. My 10 foot tunes 30 and 17 but usually not 20 (SWR over 2:1) unless I move it around to a sweet spot in my yard. Yeah it's like that.

The connection points on the rear of the tuner are only 3/16 inch so they are not heavy duty. At one time one of the connection rods rotated which shorted out the capacitor and the unit would'nt tune. If you want to construct a heavy duty loop you'll need to weld it to small lugs that fit the connectors. MFJ gives the idea this tuner is heavy duty. It's not a tank but rather a Corolla at a Mercedes price.

If you like experimenting this tuner is fine. Expect to spend 90% of your operating time setting it up and tuning it and 10% actually operating.

On the positive side I live in an RF dead zone. Nothing works at less than 50 watts - not dipoles, verticals, windoms, calmdoms, bazookas, wrigleys.
Still I can make contacts with this. The trick is to be tuned to the right frequency when some other station somewhere is on the air. You'll probably hear him well and he'll probably come back to you.
N3LCW Rating: 2010-01-01
It really works great! Time Owned: more than 12 months.
I've owned the MFJ-936B version of this tuner for 2 years now. It really does work and it works very well, and if you can get it outside or near a window it will do great.

I tried it first on 20M with a 13ft length of wire formed into a loop. Tuned it up on 14.070 and was amazed to hear loud PSK signals. I copied DX signals from South America that I could not detect with my 20M attic dipole. I had excellent reports on transmit also. 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.

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. Be sure to have a few inches space between the turns.

Another little secret: you can work 80M with a 32ft circumference wire loop 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. This extends the tuning capacity and you will be able to use the tuner lower in frequency than previously thought. 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.

Using this tuner eventually gave me magnetic loop fever and I've built many and use them exclusively at this CCR restricted QTH.

I think this tuner is an MFJ winner and am surprised it hasn't caught on yet.

Andrew N3LCW
KC2OYZ Rating: 2009-02-23
Don't expect miracles, but Time Owned: 0 to 3 months.
I'm suffering at the moment from TVI/CCR problems - have moved indoors. WA9UAA mentioned the 935b to me, decided to check it out - and it WORKS as advertised.

I haven't experienced any problems with the 935b at all - my only gripe is that the coax input should have been put in a more convenient spot - the front or side, not right next to the loop contacts in the back.

I studied up a bit on loop theory, read through the manual carefully, hooked it up and tried it out, next to my open kitchen window. I expected sparks to come flying out and the all the fuses to blow but to my surprise, nothing of the sort. I tuned it to the middle of the 20m band, did some tests, heard lots of stations and a few answered me back.

I'm using a 7 ft long piece of 3/8'' copper tubing for a loop on 20m, and I found that by tuning the loop to the middle of the band without the ATU on my rig, I could move pretty much across the whole band making up the slack with the on board ATU. The loop tuner has an RF output meter at the point of transmission so you can check your true RF output from there.

Of course the loop is highly directional but it is a GREAT antenna for RX and outdoors on a rotor of some sort it will give excellent performance on both RX and TX (it's not weatherproof).

For indoors, don't expect miracles on your TX - the laws of physics never change, especially if you're in a steel framed building like me. Experiment and be patient - I have worked France and Cuba from indoors in Brooklyn - it can be done.

73
Mikey
K2BKT