- Amateur Radio (Ham Radio) Community

Call Search

New to Ham Radio?
My Profile

Friends Remembered
Survey Question

DX Cluster Spots

Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement

Reviews Categories | Antenna parts, accessories, incl. baluns, hardware, etc. | AMIDON W2FMI Balun Transformer Help

Reviews Summary for AMIDON W2FMI Balun Transformer
AMIDON W2FMI Balun Transformer Reviews: 7 Average rating: 3.6/5 MSRP: $69.95
Description: W2FMI high-power balun
Product is in production.
More info:
Email Subscription
You are not subscribed to this review.

My Subscriptions
Subscriptions Help

You can write your own review of the AMIDON W2FMI Balun Transformer.

N3JI Rating: 4/5 Aug 24, 2009 15:10 Send this review to a friend
Good Balun  Time owned: more than 12 months
No problems at all with mine -- it's the 1:1 version, and I've had it in use for several years. I have run it full-bore with my Henry 3K-A (legal limit++) into my homebrew G5RV in an inverted V, 50' to the apex, about 30' at the ends. Has been working great the whole time, and now I'm running it into a homebrew W5GI Mystery Antenna (similar to a G5RV) in the same configuration at legal limit.

I would've given it a 5, but I thought it necessary to seal up the case with silicone since mine lives outside 100% of the time at end of the 33' of twinlead. Didn't think it would be good having water & critters getting in there over the years. I noticed no issues when I had it open with the wiring. It wasn't open magnet wire either, I don't think, but it's been too many years since I've looked at it.

I would recommend it to anyone needing a heavy duty balun.
W7JK Rating: 0/5 Feb 2, 2008 23:39 Send this review to a friend
Quality Control Issue  Time owned: 0 to 3 months
My 4 to 1 Balun worked great until it started to arc causing my amps protection to activate. The problem was due to the way that it was constructed. For the information of those that might not know the toroid inside this Balun is wrapped with bare magnet wire that is supposed to be slipped into continuous lengths of clear tubing to insulate the wires. It seems that they didn't have enough tubing to keep it continuous so more tubing was added leaving two breaks which is where the arcing was occurring. The person that assembled this Balun thoughtfully covered the breaks in the insulation with white tape so if you looked it wouldn't be apparent.

I have made Amidon aware of this issue.
WB1AEX Rating: 5/5 May 8, 2007 14:35 Send this review to a friend
Excellent Results  Time owned: 6 to 12 months
I mounted a 4:1 version of one of these at the top of a 10 foot steel TV mast pounded into the ground to feed a 260 foot ladder line center-fed antenna. The apex of the inverted v is at 70 feet and I use about 85 feet of ladder line to reach from the balun to the antenna feedpoint. I run 18 feet of RG-213 from the balun through a sill plate into my station's T-match. It works very well on 160/75/60/40 meters running up to a kilowatt (except for 60 meters of course). Excellent signal reports, no problems finding a match, and no RF in the station. I sealed up the seams of the balun's aluminum housing with GE Aluminum and Metal Silicone II sealant which I picked up from my local True Value Hardware store. It has survived a New England summer and a winter with no ill effects. It is sturdily constructed and uses stainless hardware for the connections. Very nice build quality. I have no problems recommending this balun to anyone looking for a high power solution.

K0ZN Rating: 5/5 Jan 16, 2003 23:50 Send this review to a friend
Excellent Balun  Time owned: more than 12 months
I have several of the Amidon/W2FMI baluns. I have had Zero problems and they function as advertised.
I have used the 4:1 "high power/high SWR" balun at 1,200 watts output in a high SWR condition (450 ohm line to a C.F.Zepp) in long CW QSO's and had no problems, nor could I detect heating. As far as I can tell they are supurb. The aluminum housing isn't exactly "bomb proof", but it is adequate. I have had no weather or moisture related problems. I would buy them again without hesitation.

FYI. The Amidon/W2FMI UNUN's are also great: put them on the INPUT of your tuner to extend the range if the tuner can't transform the output/input impedance ratio enough to make a 50 ohm match. By using an UNUN to reduce the ratio that the tuner has to match, tuner losses are reduced. The UNUN's can significantly extend the range of some tuners. The UNUN's are a slick little device.

73, K0ZN
K7NA Rating: 3/5 Jul 16, 2001 00:16 Send this review to a friend
Not Useful on the Upper Bands  Time owned: more than 12 months
The HBHT-200 is well constructed and of subtantial build quality. It appears to work reasonably well on the lower bands. But, like all 4:1 baluns, it suffers the same problems that all other baluns do when used on the bands above 10 mHz: poor balancing of currents on each feeder wire. For an explanation of why this is so, see Rich Measures discussion at :

For fun, try measuring the current in your ladderline on the higher bands when you are using the built-in balun in your MFJ or other unbalanced T or L-circuit matching network employing a balun in the output. You may be surprised at what you find.

Vince K7NA
W1HIS Rating: 4/5 Oct 29, 2000 15:34 Send this review to a friend
Good, well designed & built  Time owned: 0 to 3 months
I bought the 1:1 version from Amidon, and as soon as I got it I opened it up, inspected, and measured it. It's well constructed and well designed, naturally in accordance with W2FMI's textbook. It tolerates severe mismatch at modest (200 W) power much better and has much less loss than the balun it replaced, which I'd made myself from an FT-240-43 toroid. I haven't tested it with high power yet.

I wish its common-mode impedance were higher. (Its c.-m. inductance is only 35 microhenries.) Still, I prefer it to RadioWorks' baluns, which I also have. Although it's not weather-sealed, that problem is easily solved, and it has better cooling and fire safety due to its metal case.
K4TAX Rating: 4/5 Mar 29, 2000 18:50 Send this review to a friend
Good buy and a solid performer  Time owned: unknown months
Needing a high power balun I choose the W2FMI balun by AMIDON. Rated for high power, upwards of 5KW, it serves me well between my tuner and a balanced feed system on a 256 ft center fed wire. It is used on 160M - 10M. In measuring the balance, I found it to be within 3%. With a 4:1 transformation ratio, it allows my unbalanced tuner to feed any impedance from 5 ohms to over 3000 ohms, any phase angle, at legal power. Certain operating conditions produce a SWR in excess of 10:1 without any evidence of heating at 1500 watts. While the enclosure is not truely waterpoof, the additiion of 100% silicone at the seams closed it up nicely. If it were weather tight I'd rate it a "5".

If you have any questions, problems, or suggestions about Reviews, please email your Reviews Manager.