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Reviews Categories | Antenna Tuners | MFJ-939 automatic antenna tuner Help

Reviews Summary for MFJ-939 automatic antenna tuner
MFJ-939 automatic antenna tuner Reviews: 26 Average rating: 3.9/5 MSRP: $159.95
Description: 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.
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K8DXX Rating: 5/5 Jun 19, 2016 20:00 Send this review to a friend
Quick Test Very Positive  Time owned: 0 to 3 months
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.
K0BEL Rating: 5/5 May 24, 2016 12:52 Send this review to a friend
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: 0/5 May 18, 2016 05:45 Send this review to a friend
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!
KD2JVX Rating: 5/5 Apr 7, 2016 14:55 Send this review to a friend
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: 5/5 Apr 2, 2016 16:13 Send this review to a friend
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: 1/5 Mar 20, 2016 12:06 Send this review to a friend
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: 5/5 Feb 21, 2016 16:43 Send this review to a friend
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: 5/5 Feb 6, 2016 18:40 Send this review to a friend
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: 1/5 Jan 31, 2016 19:34 Send this review to a friend
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: 2/5 Jan 31, 2016 17:36 Send this review to a friend
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.
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