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Reviews Categories | Antenna Tuners/Matching Networks | MFJ-212 Help

Reviews Summary for MFJ-212
MFJ-212 Reviews: 11 Average rating: 4.9/5 MSRP: $79.95
Description: MFJ-212 Tunes up your antenna tuner without transmitting a single milliwatt! No power. Precisely tune your antenna tuner for a 1:1 SWR -- no additional "tweaking" needed. Avoids overheating/arcing caused by high SWR and long tune-ups. MFJ's RF*Guard bypasses the MFJ-212 to prevent damage. Handles up to 300 Watts. Works with all radios 160-6 Meters. 3 1/3 x 1 1/4 x 4 in. 9-12 VDC or 110 VAC with MFJ-1312D, $14.95
Product is in production.
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AB7DP Rating: 5/5 Mar 18, 2017 10:11 Send this review to a friend
Great for Tuning Small Loop Antennas  Time owned: 0 to 3 months
Picked up a MFJ-212 at the local Hamfest and found it works great for tuning small magnetic loop antennas, without having to transmit.

Many transceivers do not have an easy way to emit a low powered carrier for tuning but this is very accurate and won't emit unnecessary RF for tuning.

The MFJ-212 is connected between your transceiver and the loop antenna. Turn on your transceiver and tune your loop as usual for maximum receive noise. This gets close to resonance or ballpark in most cases.

Then, turn on the MFJ-212. The unit will produce a pulsating, white noise from the transceivers speaker. Then tune your loop until that white noise disappears. It is now tuned, then turn off the unit for transmit.

I found that using the MFJ-212 I can precisely tune my small loop to resonance, I would recommend this to other small loop users.
VK7JB Rating: 5/5 Feb 22, 2017 02:24 Send this review to a friend
I wish I'd discovered this years ago...  Time owned: 0 to 3 months
This is a great device -simple in its design but so easy to use, so effective and so compact. I can now adjust my manual tuners in a few seconds without contributing any RF to an already polluted spectrum. The pulsed noise null is very clear and deep and after tuning for that null, the SWR on the line between the tuner and rig is always exactly 1.0:1 on my LP-100A meter. This accuracy is maintained across all the HF bands. I'm amazed by the ease of the whole tuning process with this gadget and I'm happy knowing I'm protecting my finals. On its arrival downunder,I opened my unit up, skeptical about MFJ QC after previous negative experiences, but the workmanship inside my 212 is very neat and tidy with high quality components and some obvious attention to detail in the soldering and wiring. I'll be buying another soon, just in case they go out of production and I'll be using it portable too because it can be powered by an internal 9V battery. I'm sorry it took me so long to find this gadget and I don't understand why they're not more popular. We'd all be spending much less time fiddling with notch filters if they were.
W6LZC Rating: 5/5 Mar 3, 2015 21:16 Send this review to a friend
Excellent tool  Time owned: 0 to 3 months
My working condition at my station includes Yaesu FTDX-1200, a Palstar AT2KD antenna tuner and a 160 meter doublet which is fed with ladderline. It has become a tedious job tuning the manual tuner. The Yaesu FTDX-1200 doesn't have a reduce power button and I would have to reduce power manually each and every time for tuning and after tuning return back to full power. There has to be a better way. I read about the matchmaker in eHam that I decided to give it a try. Not surprised about MFJ QC given that my first unit failed to work after installing. I was glad that HRO-Burbank had more than one unit available, so was able to exchange it for another one. This time, the replacement unit worked. This device does work as it was designed and it really helps with tuning the manual antenna tuner without having to apply any rf power. The results are amazing. I have been able to tune the Palstar quickly and obtain every time a 1 to 1 match. It is so easy to use. I highly recommend this device for the ham that uses a manual antenna tuner in their station.
W2DI Rating: 5/5 Jan 4, 2015 11:04 Send this review to a friend
Wonderful accessory  Time owned: more than 12 months
This unit really works well when using a manual tuner. You can set the tuner without transmitting any signal and, for my set-up, it's spot on!
It does help to turn down the rf gain to really hear the null.
I use 12 v rather than the battery.
It's a good idea to take some time, initially to find the best tuner settings on each band you use and write them down. On the lower frequencies (40m) I do this for every 50 kHz or so. That way you're in the neighborhood and then just use the 212 for touch-up.
No signal transmitted until you're ready to speak or key. Might save some stress on the rig.
Thanks for reading.
K8NDS Rating: 5/5 Jan 4, 2015 07:56 Send this review to a friend
Great product  Time owned: more than 12 months
Again I will repeat my earlier review. Contrary to the previous review my MFJ-212 coincides with the lowest VSWR 100% of the time. Several others that are running my antennas are also using them with the same performance. I tune my Helical Loops using this device religiously, all my other VSWR instruments agree 100% for the lowest SWR point.Although I do agree that MFJ should supply schematics so that competent operators can troubleshoot their own equipment. I have also had issues in this regard in the past with other MFJ equipment that I own.
Conclusion is that it is a fine piece of equipment but I hope it doesn't fail like some of the other things of MFJ that I have owned. So far about 2 years for this one with no issues.
N1CKX Rating: 4/5 Jan 3, 2015 19:58 Send this review to a friend
Works, Needs Help  Time owned: more than 12 months
A couple of years ago I “rolled my own” version of a pulsed noise bridge and was extremely happy with the results. Adjust the tuner to “Null” the pulsing noise and when I transmitted the SWR was Perfect.

However my home made unit was built on three separate boards and in a large 4” X 4” X 8” enclosure and took up a lot of space.

Enter the MFJ-212, compact and attractive when sitting amongst the rest of my gear.
The fly in the ointment is due to manufacturing variances (component tolerance variations) the point where the MFJ nulls is not the lowest SWR point. That is, something in the MFJ bridge is slightly off.

My own version had a trim cap to accurately balance the bridge at 50 ohms.

I opened up the MFJ unit and there is no such cap/adjustment available. And to make things worse MFJ is starting to eliminate schematics.
This was the one saving grace to MFJ products. They Usually had complete Schematics, AND USUALLY NEED THEM.

The board is double sided and not clear where anything goes, so this unit is back sitting on my bench until I find the time/patience to “reverse engineer” the thing.

My home brew unit is back in service.

Cut the crap MFJ, it doesn’t cost anything to print the schematic in the manual, and let’s face it.
Without schematics I have no incentive to buy as I Know it will need work
KF4CQR Rating: 5/5 Sep 24, 2011 14:21 Send this review to a friend
Good Device  Time owned: more than 12 months
1. Works as advertised. Good piece of equipment for tuning up without a carrier and bothering your fellow hams.
2. Caveats:
a. Draws a little over 100 milli-amps – will kill a 9v battery in a relatively short time… just a few tune-ups into an antenna you have no idea where the initial antenna tuner settings should be and you have a dead 9v battery (I was not using an Alkaline 9v… just a cheap one).
b. Null is sharp. Unless you know the general settings of your tuner before staring the tuning process, be prepared to make small adjustments in your tuner’s parameters when tuning into an unknown source (random wire antenna for example).
3. I bought this product about one year ago. Original intent for the purchase was to tune a QRP rig in a field environment. Be prepared to make small adjustments on your antenna tuner as the nulls are rather sharp and you can miss the “sweet spot” if you are not careful. An analog SWR meter gives you an indication your antenna tuner settings may be “getting there” before your ear can detect a change in the background noise. Keep that in mind when deciding on what to use.
4. The built-in by pass relay and RF detection circuitry have saved my butt on several occasions when I accidentally keyed 100 watts PEP into the system while the device was on. The MFJ-212 safely by-passed the RF and was not damaged.
5. You would have a hard time trying to homebrew this device yourself for less money unless you had a junk box from heaven available to you.
6. General Antenna tuner comment: To this very day, I do not understand why people disparage the use of an antenna tuner, especially when dealing with a resonant antenna. These Hams are limiting themselves to a narrow range of frequencies (especially on 80 meters). Using an inexpensive tuner will allow you to easily work the entire 75-80 meter band on a simple wire dipole with basically no noticeable loss in signal strength from increased SWR on a coax feed line. Get/make a tuner and enjoy increased frequency flexibility.

N2EIK Rating: 5/5 Jan 21, 2009 02:33 Send this review to a friend
Great!  Time owned: 0 to 3 months
I found that in order to use this device I need to turn my RF gain down to 50% and turn my pre-amp off. The 212 work like a charm every time, 1:1.
I wish I could have found one used, cheaper but I couldnt and bought new at $100... but overall money well spent and I can see why I couldnt find one used for months, I know I wont part with it! Closest thing to an auto-tuner!
Rig- Kwd TS-B200, Tuner, ATR-30
KJ4CNN Rating: 5/5 Sep 28, 2008 17:59 Send this review to a friend
Super Device for ham shack  Time owned: 0 to 3 months
This little box has been the difference between getting on line and not. With an end-fed, long wire antenna strung through a dense crop of trees (not the best type of an antenna area) I couldn't get my SWR down enough to reach out. Also with an older tube transceiver (Yaesu FT-101EX) I just did not want to burn out my final tube with extended tuning. Now, however, I just turn this box on, twist a few dials until the tone goes away and I am set to go.
The first day that I used it I worked 80m all night; almost was too tired to go to work the next day. Super product!
KM5TC Rating: 5/5 Dec 22, 2007 06:54 Send this review to a friend
Neat device  Time owned: more than 12 months
Bought the MFJ 212 from a fellow ham.
This works with my Icom 718 and MFJ 949E tuner.
Set your radio to desired band/freq, turn the
212 on and it emitts a pulsing noise,
set your inductor switch, turn trans/ant knobs
until you hear a null in the pulsing noise and
you have 1:1 or 1:2 swr readings on the tuner
and you're ready to. 73's
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