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write your own review of the MFJ-971.
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KJ4NGS
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Rating: 2/5
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Oct 27, 2009 10:01
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Open it up and inspect it first!
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Time owned: 0 to 3 months
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I have a small corner of a desk for all my equipment, so I was attracted to this unit for its size, cost, and ability to handle my transmitter's output (200w PEP SSB).
But as I started working with it, my nose told me I was frying something inside ...
Opening it up revealed the following issues with my unit:
(1) The "Antenna" variable capacitor was misaligned, and so it was shorting out in most positions. Much time was spent re-aligning the blades.
(2) The knob on the "Inductor" rotary switch was not set properly, and so when I thought I had a mid-range inductance selected it really was basically shorting the TX to ground.
As a result of (2), it started to smoke the inductor switch as it was shorting out the transmitter. (The rotary switch is not designed to handle much power, I suspect!) The schematic is clear that the "A" position was a short (why do they even do that?), but the H position I thought I was using was a fair amount of inductance.
I clipped the real "A" connection internally (I never want to accidentally short TX to ground, thank you very much), and re-aligned the knob, and now things seem to be working OK.
I guess I didn't let ALL the smoke out of it yet! ;-)
So if you're lucky, you'll get a unit where both variable caps aren't shorted and the knob is set right and all will work well for you. If you're not lucky, and don't correct the problems in it first, you can fry the unit. I imagine this explains the disparate reviews I see here in eHam.
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N3NXD
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Rating: 1/5
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Oct 2, 2009 18:51
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Poor Quality Control
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Time owned: more than 12 months
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Bought mine new April 2008. Used to tune up Icom 718 Transceiver. 100 watts.Noticed at times a fluttering of the cross match needles during TX. Finally It totally quit After warranty ran out, by 2 days.
Took case apart. Blown, cheapy made plastic band switch. Replaced with ceramic one from junk-box. Visual of inductor coil connections showed close coil winding to coil winding distance, and poor soldering. resoldered, and bent coils apart for more distance. Checked variable capacitor. Some plates barely brushing against rotor frame. Noticed charred material between some ( the fluttering needles) arcing. respaced plates. Took pipe cleaner and alcohol, removed considerable dust from between plates. Now works like a champ. No arcing.
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OLLIEOXEN27
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Rating: 1/5
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Jul 20, 2009 08:27
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SWR roller coaster
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Time owned: more than 12 months
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A lot of these 971s are made with pop rivets instead of tapping screws. Thus the SWR is unstable - all you basically have to do is bump or move the tuner and the SWR will show it. Another problem with MFJ tuners is faulty SO-239s whose center pins are improperly mounted in the casings. Buy at your own risk. Don't say no one ever warned you.
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K5III
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Rating: 5/5
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Sep 27, 2008 20:30
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Great little tuner
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Time owned: more than 12 months
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I've owned my tuner for over 7 years now. I picked it up on eBay almost new in the box. I agree that MFJ has some challenges in the design on some things, however, this was one that was done right. It has performed flawlessly. The power reading is as accurate as you could get with a cross needle analog meter. If for some reason it is off slightly, it can be easily tweaked. It is light, easy to take with you, will tune a random wire with no problem. If you have problems using this tuner, then you would have problems with any manual tuner. It easy to use and great for QRP. I've used mine from 5 to 100w, and it worked every time. I am well please in the performance and price. The only negative is no bypass switch, but I haven't really missed it.
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N2UGB
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Rating: 4/5
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Jul 5, 2008 10:53
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Very nice QRP! Tuner
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Time owned: more than 12 months
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Set up with my FT-817ND and OHR-500. So, it is used as advertised...a QRP antenna tuner. Matches all the compromise antennas I am forced to use, including my Buddistick.
I have found the QRP power indication to be reasonably accurate. My OHR QRP wattmeter and the MFJ are pretty close, though the OHR is used when great precision required.
A a QRP op, I prefer having one less coax "patch" which is the case when using the 971.
I give it a 4, not because of performance, which is FB, but because of the small display that can be difficult to read for the tri-focal crown...of which I am a member.
I wouldn't bang it around.
A bypass switch would have been helpful, but I knew it wasn't there when I bought it, so I can't fault MFJ for that.
I like it and use it exclusively. On my operating position right now.
I have two of 'em.
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IW1DFU
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Rating: 3/5
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Jun 29, 2007 03:41
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so and so...
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Time owned: more than 12 months
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I've had one for more than one year and here you'll find some comments about it:
1) probably it's really good for QRP operation but if you try to use with something like 100W you'll sure have some problem: I've burned the inductance switch in few minutes... replaced with something better, it has worked fine but with some spikes on the capacitor (sometimes...)because they has really poor spaced.
2) it hasn't got the bypass switch... And you'll need it!
73 de Fabio, IW1DFU.
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OE3SGU
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Rating: 4/5
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Jun 28, 2007 09:15
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Good portable tuner
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Time owned: 0 to 3 months
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Recently bought one and it works just fine. Tried it with power levels up to 100 W and there are no problems with it. It fits nicely to my MFJ-9020 QRP rig. The only downside is that there is no bypass-switch.
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W5VK
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Rating: 4/5
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Mar 26, 2007 01:08
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Acceptable
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Time owned: more than 12 months
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I wanted a small flexible tuner for my IC 706G "jump bag" and the 971 meets my needs. I bought this new at Dayton and I've used it for 6 years without problems. MFJ tuners do have their share of QC problems but I found (after "frying" a few) that if you tune them at low power and then apply power, they will usually operate within specifications.
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AB7JK
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Rating: 1/5
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Feb 5, 2007 13:20
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bad capacitors
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Time owned: 3 to 6 months
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These units work ok unless you get one used like me with some capacitor plates touching. They are more difficult to adjust than you think. If anyone sees Mr. Jue laughing all the way to the bank they should shoot him in the butt just for the fun of it.
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SWDUNCAN
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Rating: 2/5
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Aug 8, 2006 05:45
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useless for QRP
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Time owned: 0 to 3 months
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As a tuner, it's just fine, but even in the 6 watt sensitivity and switched to the 6 watt range, the forward power is very inaccurate. I was looking for a tuner that would work with my FT-817ND. The tuner is in the "return mode" as I write this review. How this can be sold as a QRP tuner is beyond me. The following is a response to my inquiry from MFJ tech. dept.:
"the 971 meter can only register accurate at six watts. any power below that
will be inaccurate due to the six watt limitation to the tuner. it can be
recalibrated but anything below six watts is still going to be inaccurate.
thanks for your business."
Seems to me, a 6 watt scale should be able to measure .5 watts to a max of 6 watts.
scott
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