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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
KD2JVX Rating: 2016-04-07
works great with the ic-7100 Time Owned: 0 to 3 months.
I was able to tune up a random wire and work 17m and 20m with no effort and get 1.5 SWR. Signal report from Italy was only 3 but i attribute that to the ground.
NH6RF Rating: 2016-04-02
Works fine for me Time Owned: 3 to 6 months.
Ordered direct from MFJ. Took awhile to get it because they were back ordered. Set up is simple and it worked as described. I'm using with a Yaesu FT-840 into a 67 foot Off Center Fed Dipole. Although antenna is designed for 40 meters and up, I've made many long distant contacts on 80 meters. I have the MFJ-874 SWR/Power meter installed. Like the Tuners manual says, 1 beep from the tuner after tuning is complete indicates an SWR of 1.5:1 or less. That's what I'm seeing. For me this tuner is working great.
AC2KZ Rating: 2016-03-20
Keeps locking up! Time Owned: 0 to 3 months.
Keeps going into bypass mode, then locks up. Only way to get out of lockup is to shut it down and start over, repeat.
Not very happy with this tuner, only have it a week. Since today is Sunday, will try to return tomorrow.
N5MNO Rating: 2016-02-21
greta mobile tuner Time Owned: 3 to 6 months.
I use this tuner in my vehicle with a ts-480hx.
it tunes my hustler verticals just 200watts ssb and also use it for mobile rtty, cw and PSK all digital modes
W5KAO Rating: 2016-02-06
Ideal tuner, at least for Icom users. Time Owned: 0 to 3 months.
Bought this tuner during Christmas sale at Gigaparts. Using it with my Icom IC-718. Works perfectly! Can't be better! Recommend to all Icom users. It looks like there are some problems at least with some of the Yaesu radios, so, please, do your homework before you buy it.

Now trying to figure out how to use it with my spare rig (Kenwood TS-130SE). I definitely need it for my fan dipole at 80m (the best resonance is with SWR 2:1 :-( due to interaction with other bands and low hight).

For relatively new Icoms it works flawlessly.
KF5UEZ Rating: 2016-01-31
Not for Yaesu FT-450d or W8AMZ ZS6BKW /G5RV Time Owned: 3 to 6 months.
I own the Yaesu FT-450d and I am really enjoying the radio when you consider its cost and features. However, the built in tuner does not do will with my “W8AMZ ZS6BKW /G5RV” which is at 40 feet in an inverted “V”. So I bought the MFJ-939 Tuner for FT-450d. Well it DID NOT WORK – could not tune 10, 15, or 80 meters. Non the less it is boxed new in my cabinet in my shack. I bought a LDG YT-450 (newer version is LDG YT-1200) it tune quickly and very well on 6 – 80 meters. Do Not waste $$$$ on MFJ-939 for your Yaesu FT-450d.
KW4MG Rating: 2016-01-31
Doesn't work with 450D. Time Owned: 0 to 3 months.
I had the same experience documented by other Yaesu 450D owners. On arrival unit did not work, MFJ sent me a new IC chip to install. It worked the same as the original (meaning it did not work). Sorry to say unit went back. I had high hopes with all the hype about this unit.
ON6KE Rating: 2015-12-27
Good ATU but not proactive Time Owned: 0 to 3 months.
It's a good tuner and fast indeed.
There's but 1 point that's a little disappointing, it being connected via the interface cable to the TS-590SG one would expect to see the LC settings set each time one changes band or moves to the far other side of the band, not so, it changes its settings only AFTER having sent a carrier.

The 590SG's ATU settings ARE changed when changing band WITHOUT a carrier being sent.

Gust ON6KE
K2OWK Rating: 2015-12-25
Excellent tuner Time Owned: 3 to 6 months.
I have had this tuner a few months now. It is the best tuner I have ever used. I have an S9 32 foot antenna with about 20 radials and a 4 to 1 UNUN. This tuner tunes all band from 160 thru 6 meters. (yes it does tune 6 although it is rated thru 10 meters). As the manufacturer indicates it learns the frequencies you use, and when you go back to these frequencies the tuning is just about instantaneous. Even on a new frequency it tunes within a second or so. Its tuning range is spectacular. My antenna has a VSWR on 160 meters of about 25 to 1 this tuner manages it with without a problem. I most likely get out super low power on this frequency, but it does tune it. I would recommended this tuner to anyone with a standard transceiver up to 2009 watts. Just select the frequency and talk. I can not praise this tuner enough. My radio is a Yaesu FT-450AT which is a plug and play with the included cable. Just have to disable the internal tuner.
K4MZR Rating: 2015-12-17
Waiting Time Owned: 0 to 3 months.
Update 3: 17 Dec

After not hearing back from MFJ I contacted them and was informed their engineer was confused and surprised that the last firmware update did not resolve the Yaesu Ft-450D interface issue. No resolution was offered, simply another promise to call me when they find something. This unit gets a decent review in the Jan QST but that article does not reveal the problems Yaesu FT-450D users are having. If you're a 459 owner and need a tuner I'd recommend looking at other models for the time being.

I'll update again if MFJ figures anything out.

Update 2

I received the new chip from MFJ and installed it in the 939 and ... nothing. The tuner exhibits the exact same behavior. I contacted MFJ's tech support and they seemed surprised and confused; they obviously thought their firmware update had resolved the issue. They are supposed to consult with their firmware engineer and follow up with me next week.

For another account of this issue between the Yaesu FT-450D and the MFJ 939 see:

--- Dec 7 Update ---

This is an update to my original review (below). I contacted MFJ about the issues I was experiencing and the tech immediately confirmed it was bad firmware ... the same issue that had supposedly been resolved when I first inquired about the unit. Regardless, he was quick to own the problem and offered a pre-paid return or the option to replace the offending chip myself. I opted for the latter.
After much experimentation I have determined the tuner will function if presented with a 20w CW on any desired frequency. And it does allow me to tune quickly on 80-6m. But in its current guise it is far from the advertised plug-and-play. Right now it's better than the original 0 rating but it doesn't merit more than a 2 unless MFJ's chip replacement allows it to integrate with the radio as advertised.

-----Original Review-----
Received the MFJ 939 as an early Christmas present for use with my FT-450D. Set it up per the instructions and was truly disappointed to find out how inefficient and buggy this unit is. It will often refuse to drop the tuning carrier, leaving the radio stuck in transmit until powered down. It regularly refuses to tune frequencies the 450's internal tuner handles without a problem. And, most frustratingly, it often just stops responding all together.

I had read of some of these issues from other FT-450D users and they said MFJ attributed it to either bad cables or the wrong firmware. I did call MFJ prior to ordering and was assured all those issues had been resolved ... obviously not! This one will be going back in the morning.