MFJ-939 Automatic Antenna Tuner

5stars

MFJ-939 Automatic Antenna Tuner Review

Street Price: $159.95

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6 User reviews

5stars


Editors rating

  • Ease of use
  • Price
  • Asthetics
  • Tuning Speed
  • Feature set
What a superb piece of gear for anyone operating HF bands. The MFJ-939Y automatic antenna tuner is a perfect match for my Yaesu FT-450. One of the greatest features of this tuner, compared to an autotuner like the LDG YT-100, is the ability of use it with ANY HF radio.
Street Price: $159.95

What a superb piece of gear for anyone operating HF bands. The MFJ-939Y automatic antenna tuner is a perfect match for my Yaesu FT-450. One of the greatest features of this tuner, compared to an autotuner like the LDG YT-100, is the ability of use it with ANY HF radio. So you don’t have to purchase a new tuner if you decide to switch to an ICOM. You can buy an inexpensive plug-n-play cable for just about any modern rig for the fastest tune possible, or skip the plug-n-play cable and the tuner will tune as soon as it detects RF.

The MFJ-939 has more inductors, capacitors and relays than any of its competitors which will give you a lower SWR across a wider range. For example, on roller inductor manual tuner, I can never obtain better than a 2.5:1 SWR on 75 meters, but the MFJ-993 got the SWR down to almost a perfect 1:1 match the first time. The matching range on this autotuner is 6-1600 ohms, so it’ s not surprising it had no problem with my antenna on 75 meters.

The instant recall feature makes it even better. When you tune on a certain frequency, it remembers the exact capacitance and inductance used to make the match in one of its 20,000 memories built in. So when you switch bands and return to a previously used frequency, it’s almost instant to make the match. The more you use this, the more it learns from you. Eventually you will be casually operating and tuning across the HF spectrum and you will forget it’s even there. Compared to other autotuners, the MFJ-939 is a little quieter than most.

Another great feature is the ability to manually tune, so if you want to listen outside of the ham bands where you cannot transmit, holding the tune button for 1 second will tune it for you. It’s just the right size to fit on top of my radio and requires minimum power, so it’s also ideal for Field Day operations or portable use.

It’s just the right size to fit on top of my radio and requires minimum power, so it’s also ideal for Field Day operations or portable use. An excellent upgrade from my trusty MFJ-969 roller inductor tuner I have used for years — I no longer have to turn and turn the dials and try to zero in before the DX contact is long gone.

Conclusion Rating
Overall this unit is easy enough for the newest operator to setup and use and has the features and capabilities that the most seasoned operator will enjoy.
5 stars

6 Comments

  • Eric KJ4YZI says:
    5 stars

    What a superb piece of gear. Small enough to take with me on field day or a remote location. Tunes my OCF dipole to a 1.0:1 SWR almost every single time. Manual tune feature is a plus for listening outside the ham bands where i can’t transmit. The best part is it works with almost any HF radio with an additional interface cable. Simple enough for even the newest operator to connect and use. So far it has not given me any grief, and my hand sure did get a break from the trusty MFJ roller inductor tuner. MFJ has always amazed me, and i will continue to support their product. A+

  • Eric KJ4YZI says:
    5 stars

    What a superb piece of gear for anyone operating HF bands. The MFJ-939Y autotuner is a perfect match for my Yaesu FT-450. One of the greatest features of this tuner compared to an LDG autotuner is the ability of use it with ANY HF radio. So you don’t have to purchase a new tuner if you decide to switch to an ICOM. By simply connecting this unit inline with your radio and feedline and transmitting a carrier, the circuit detects the high SWR and begins its process of finding a perfect match for your transceiver. This process takes only a second. This tuner uses many inductors, relays and capacitors to compute the best match, and a total of like 134,000 possibilities in the algorithm. In comparison to my MFJ roller inductor tuner, i can never obtain better than a 2.5:1 SWR on 75 meters. When i first used this autotuner, i was curious to see what would happen with my radio at 75 meters. And it found a perfect tune at 1.0:1 SWR the first time. The matching range on this autotuner is 6-1600 ohms. Not a suprise to me that it worked perfectly on 75 meters.

    The instant recall feature makes it even better. When you tune on a certain frequency, it remembers the exact capacitance and inductance used to make the match in one of it’s 20,000 memories built in. So when you switch bands and return to a previously used frequency, it’s almost instant to make the match. The more you use this, the more it learns from you. Eventually you will be casually operating and tuning across the HF spectrum and you will forget it’s even there. This unit is not that loud at all for all the relays that are built in.

    Another great feature is the ability to manually tune, so if you want to listen outside of the ham bands where you cannot transmit, holding the tune button for 1 second will tune it for you.

    Overall this unit is easy enough for the newest operator to setup and use, and the seasoned operator will most definitely enjoy it as well. This unit is small, not as big as my FT-450 so it sits very nicely on top of my radio. Requires minimum power, so this would be a great piece of gear for field day or a remote location while traveling. Light and compact is always a plus when traveling. Plus my hand has thanked me for the break from my trusty MFJ-969 roller inductor tuner i have used for years, i no longer have to turn and turn the dials and try to zero in before the DX contact is long gone.

    MFJ has always amazed me and i will continue to support their products. A++

  • Eugene Douglas says:

    I am wondering if it will tuner 6 meters? I looked and did not see if it could. Maybe I missed it.

  • Merle Watts says:

    I have a 939b and it is speced to 10 meters. I have been using it on 6 meters and it works fine. I would say give it a try. It might work.

    • Trevor says:
      5 stars

      Yep, it works just fine on 6m for me. And I discovered that accidentally. I tuned on 6m, made a contact, and then realized it wasn’t supposed to work! 🙂

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