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Reviews For: MFJ-939 automatic antenna tuner

Category: Antenna Tuners/Matching Networks

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Review Summary For : MFJ-939 automatic antenna tuner
Reviews: 43MSRP: 159.95
Plug & Play! You won’t even know it’s there . . . MFJ-939I/K/Y automatically tunes your antenna as you tune your radio. SWR is just always low.

Tunes your coax fed or random wire antennas 1.8-30 MHz from 2 Watts QRP to full 200 Watts SSB/CW.

Matches 6-1600 Ohms (SWR up to 32:1) -- that’s a 50% wider matching range than competing products that are less capable and higher priced . . . and it’s made in the USA.

Highly intelligent, ultra-fast tuning!
As you’re ragchewing, contesting or DXing, the MFJ-939 is learning your antenna and the way you operate and storing all this in its 20,000 memories. The more you use it, the more it learns.

Measure & Compute = Instant Match
MFJ-939 uniquely measures your antenna’s complex impedance (R, X), computes the L-network and snaps in needed components for instant matching.

AdaptiveSearch determines a sub-set of all solutions that can provide a safe match and searches only that subset giving
you an ultra fast match. Others search slowly through all solutions.

InstantRecall first checks its memory to see if you have operated this frequency before. If so, tuning is instantaneous and you’re ready to go!

MFJ VirtualAntenna Memory
MFJ exclusive VirtualAntenna Memory system gives you 8 antenna memory banks of 2500 memories each.
You can use an antenna switch to select up to 8 antennas and assign each antenna its own 2500 memories!

4 Times More Solutions and Faster!
MFJ has 256 values each of capacitance and inductance for 131,072 matching solutions giving you a finely tuned very low SWR. That`s 4 times the 32,768 solutions of competitors using only 128 L/C values each!
Don`t be fooled by competing products claiming fast search times -- if you have a quarter of the matching solutions, of course,it takes less time to finish but it`s not faster.
MFJ`s faster speed comes from advanced technology and software algorithms not from fewer solutions.Audio SWR Meter
An Audio SWR meter beeps when SWR <1.5, 2, 2.5, 3. Alarms if >3. Audible & Visible Diagnostic messages.

Heavy-Duty Components
Heavy-duty L-network: 10 Amp/1000V relays, RF duty silver mica caps won’t burn up. Safe, reliable, continuous 200W SSB/CW.

As Small as Your Radio
Tiny 6 1/2W x 2 7/8H x 8 3/8D”. 2.4 lbs. SO-39s, random wire ant. & gnd posts.

Never Obsolete . . . Super Versatile
Truly Plug & Play! No settings, only one cable to plug in! Order MFJ-939I, Icom; MFJ-939K, Ken; MFJ-939Y, Yaesu. Specify Yaesu: FT-100/450/950/ 857/897/1000MP/9000/2000 or other.

Never Obsolete!

If you get a new transceiver, simply order a new Plug and Play cable.

Super Versatile! Works with ALL older rigs, classic transmitters, Flex, Elecraft, Tentec, QRP, others. Auto tune antenna -- touch tune button on any MFJ-939I/K/Y for any rig.

2-Year NoMatterWhatWarranty
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
K8DXX Rating: 2017-06-28
Provided Excellent Service During 5 Month Florida Vacation Time Owned: more than 12 months.
This is a follow-up to my 2016 review. My MFJ 939I (Icom) has provided flawless service through two field Days and a 5 month Florida vacation. It just plugs into the radio. Press the TUNE button and it either goes into service and/or tunes the current load. Want to retune to get a better match? Press and hold the TUNE button for 2 seconds and it makes another attempt. In virtually all cases, it achieves a 1.3:1 or better match on each band/frequency I tried.

While in Florida, it successfully handled a DK9SQ portable wire loop from 40 - 10 meters. At best, the loop presents a 4.5:1 mismatch, worse on most bands. The only anomaly I noticed was under some circumstances, the green power light would flash on and off during transmissions. This may have had to do with being within 20 feet of the radiating antenna. Usually, retuning would make the harmless flashing light go away.

The durability of this tuner also seems good. While I carried my IC-7300 in after most operating sessions, I usually left the tuner and MFJ Mighty Lite ACPS out on the screen porch. Both undoubtedly took some wind blown rain and other abuse but suffered no functional or cosmetic effects.

For $150, you can't beat it with a stick. I continue to have good luck with a wide range of MFJ/Ameritron products. Hats of to Martin Jue and his crew!

Earlier 5-star review posted by K8DXX on 2016-06-19

Purchased the MFJ 939I for use with my Icom 7300. The instructions were apparently written for the general, non-brand specific 939 series of tuners. They clearly mention removing Jumper 4 for Icom rigs but did not mention the '7300 specifically. An email to MFJ was returned in less than 12 hours saying that my tuner, labeled on the bottom for "Icom" was preconfigured with jumper 4 disabled and would work with the IC 7300. A quick look inside the case verified jumper disabled. I was also impressed by the craftsmanship.

I own two portable antennas to be matched. The DK9SQ is a portable 64 foot wire loop held upright by light fiberglass poles. The best SWR it presents is 4.5:1 on 20 meters. The '7300's tuner wouldn't even try. The '939I gave under 1.3:1 readings on 40 - 10. The second antenna is an MFJ 2289 "big ear" portable dipole for 40 - 10. It can function as a 40 meter OCF dipole if you deploy the 40 meter loading coil. For this test, I set it up as a simple 20 meter dipole (no coil). It matched the 20 meter dipole on all bands 80 - 10. With the dipole sitting about 12 feet above ground, I worked Europe and South America on 20 & 17 meters.

I have not played with the "Sticky Tune" and other more advanced features. I used the '7300's TUNER button to turn it on, off or to retune a current setting. With the tuner's power button depressed or "on", the unit clicks when the 7300's power is turned on. Pressing the TUNER button quickly brings the tuner on or off line. Depressing the TUNER button for 2 seconds tunes/retunes. Simple as that.

In all of the above, I was operating with a 4 foot ground rod about 6 feet of wire away. I was also within 25 feet of the antennas; an RF rich environment which didn't seem to bother the radio or tuner. Think we're ready for Field Day.
K3JLS Rating: 2017-06-27
STILL Won't Work with FT-450D Time Owned: 0 to 3 months.
I read the older reviews on this tuner that stated it wouldn't work seamlessly with the FT-450D. So, I called MFJ and they reassured me that a firmware fix had been applied to correct this problem. I ordered the tuner.

When it arrived, I connected it up per the instructions. While it would tune manually (sticky tune), I would not work when the FT-450's tune button was depressed.

I called MFJ and asked about the option jumpers to be installed within the case. This unit came factory fresh with just one jumper placed on the JP2 'Y' punching. This was right, per the on-line instructions. The instructions also called for a jumper on JP4, but there was no push on jumper there, if that indeed was the proper location, nor was a spare push on jumper provided.

The fellow with whom I spoke was not that helpful and offered to have someone call me back 'later'. I told him that I wasn't interested and that I would return the unit and leave a negative reply on eHam to which he replied 'OK'.

I told him it was hardly 'OK'.
K8YZK Rating: 2017-02-07
Surprised Time Owned: 0 to 3 months.
Ok, I only gave it a 4 because no hard copy of the manual, it is online only, and it has some problems, like showing where the jumpers are. I ended up calling support and the guy I talked to wasn't sure and had to contact someone else.

Got this to use with my IC-746, which has a so-so tuner. I found that I could not tune parts of 40 meters or 80 at all, so I looked at this. After talking to a rep at Gigaparts, I decided to get one. They did not have the Icom available but had the Yaesu, (tuner comes setup and with a cable for your radio), so I had to purchase another cable, but now if I get another yaesu I am set for them.
I use a short end-fed (Maple Leaf) antenna, suppose to be good for 80-6 meters. The tuner has no problems finding a match for the freq's/band I work. Well the other night I said let's see what it does on 160, and it found a match even with this shorten antenna. Now how efficient it is, that is something different.

Overall I would recommend it, just wish the cables were a tad cheaper.
KD0USA Rating: 2017-01-28
Apply P T T your Done Time Owned: 0 to 3 months.
M F J 939Y Connected it to my Yaesu 857D with
COAX JUMPERS and Y cat cable . Used LOW power and Tuned ALL the Bands i Talk on. Increased the power
and it worked that Quick. It was press the P T T on the mic and thats it . nEXT ON my Hy-Gain 3750
i do not have a port for Electronic Tune. I sent a email to MFJ Tech . is it possible to use the tuner on a 40 year Tune & Load Rig. Reply was YES
just put your coax in and out . I did that and Lowered the Power . Bingo DONE i bought a 2d MFJ939
that day.. KD0ZK
W2QID Rating: 2016-11-15
Impressive unit Time Owned: 0 to 3 months.
I purchased the MFJ-939K to use with my various Tentec rigs and a vertical antenna. They are specifically designed for the imported transceivers but are also supposed to work with others without a supplied connecting cable. The bottom line is that it is well made and all the "IntelliTuner" features make it an awesome piece of equipment. The really negative aspect of this jump into the world of MFJ for me was the absence of any guidance in using the tuner without the connecting cable, as in the case of a Tentec. Once I removed the optioning suitcase plug everything came together. Before that it did not work properly and had a frustration level of 5 using the EHAM rating scale. Another oversight in the manual is the reference to a bias-T circuit that is actually not present.
HB9AMO Rating: 2016-10-30
Could be better Time Owned: 0 to 3 months.
I have both the MFJ-939 automatic tuner and an old MFJ-971 portable manual tuner. I can achive better results with the manual tuner than with the automatic one. In many cases the MFJ-939 refuse to tune the antenna because of too high SWR but i can get a quite good results with the manual one.
K4DZQ Rating: 2016-09-18
Filled My Needs Time Owned: 3 to 6 months.
Wanted a stand alone automatic tuner for my Flex 1500 with a 100 watt amplifier and my KX3 with a 50 watt Hardrock amplifier. Both rigs are connected to a Zero5 Vertical through the tuner. I band switch through the rigs and tune from the front panel of them also.
It is very convenient and has been problem free.
I feel that it has been a worthy purchase for me.
EA3FNI Rating: 2016-07-31
BUEN ACOPLADOR Time Owned: 0 to 3 months.
Mi experiencia ha sido muy buena despues de usar un acoplador de antena manual. Lo estoy hacienso servir con un Yaesu FT 450 y funciona estupendamente, no he tenido los problemas descritos en otras opiniones. Lo unico que encuentro malo es que no hay traducción de su manual de usuario en español u otros idiomas.
K0BEL Rating: 2016-05-24
Excellent job with IC718 and IC7200 Time Owned: 0 to 3 months.
For the price I didn't expect a lot with this tuner. But, I connected it, pressed the tuner button on my radio, the tuner would click and flash, and my swr was then fine. I used a manual tuner before this that was sometimes a pita. I would buy this again.
VE3XDB Rating: 2016-05-18
Didn't work at all. Time Owned: 0 to 3 months.
Received the package at noon yesterday. By 3:00pm it was in the mail, on the way back to DX Engineering. Here is an excerpt from the text of the email message that I sent to DX Engineering with the returned package.

"I purchased a MFJ-939K from you on May 10, 2016 and received it today. It did not work, right out of the box. Here is the sequence of events:

1. I wanted to use this tuner to tune my 40 meter quarter wave inverted L, which is resonant on 40 meters. The internal tuner on my Kenwood TS-440S/AT tunes this antenna on 40 and 15 meters, without difficulty. My primary objective with this purchase was to have it tune this antenna for 15 meters, with other rigs that don't have an internal tuner.

2. The tuner seemed to work on 40 meters, although it is so close to resonance that it may have just detected that and didn't try to tune.

3. On any other band, including 15 meters, it went into a cycle of click beep red light green light and wouldn't tune or stop.

4. I reset the tuner to factory defaults, cleared the memory and did a self test. The self test indicated pass, although the tuner clearly was not working.

5. I called Stan at MFJ and he had no solution for me, except to suggest that I add 8 feet of wire to my antenna. I did this, and as a result the tuner did not tune anywhere. So I believe the fact that it seemed to work on 40 meters was just because the antenna was already resonant."

DX Engineering was easy to deal with, but the MFJ product was very disappointing. Unfortunate, because I really wanted this to work. Had it worked, I was going to set it up for remote operation at the base of my antenna, and extend the antenna to a random length that would have worked on all bands.

I had previously been using an SG-237 at the feed point, and it worked well for about 8 years. Recently, it lost its little mind (or at least its memory) and thought it was time for something new. Now, I may open up the 237 to see if I can revive it.

Have a great day!