EFHW-8010-Is this the ultimate ‘magic’ antenna?

 Is this the ultimate ‘magic’ antenna for HF? This is the question I found at some forum topic named “Smoke and mirrors, or electro-magic”

Well, until all popular antennas such as G5RV, ZS6BKW, CHA-250, 43-foot verticals, End Fed long wire with 4:1 or 9:1 UNUNs, Open wire Doublets, Skyloops, etc. magically evolve into 8 band resonant antennas with VSWRs of 2:1 or better across all 8 bands, with matching loss (insertion transformer loss) averaging at -0.66dB from 80 thru 10m….then…

YES!  EFHW-8010-1K is the ultimate MAGIC antenna!

There is no BIG secret about the EFHW-8010 antenna, it is just a wideband low loss transformer and a piece of wire. Yes, there is a coil a few feet from the box but it is NOT TRAP, it is no secret as well, actually, everything in this antenna was published and patented by few people a long ago. First, my countrymen, Nikola Tesla patented this transformer almost 120 years ago in 1897, then another HAM, Josef Fuchs, OE1JF patented a half-wave radiator with a variation of the Tesla transformer almost 88 years ago in 1928.

Tesla Transformer
Tesla Transformer patented in 1897

Various versions of End Fed Half Wave-EFHW dipole antennas ( some with a very high matching loss) were introduced by radio amateurs in the last 80 years including mine with the best-designed broadband transformer and “Compensating” coil. This small coil is almost invisible at 80 and 40m bands but due its position and value make a nice impact on the current distribution on high bands.

For example, an EFHW-8010 antenna is half-wave resonant on 3.6MHz, it’s fundamental 8th harmonic is 28.8MHz  but due to the Velocity of wave propagation on copper wire (with insulation) and “end effect” ( first and last half-wave sections), the real 8th harmonic is above 28.8MHz. The same applies to the 7th harmonic at 25.2Mhz and the 6th harmonic at 21.6MHz.

Well, this small coil makes the wire look longer on high bands, therefore moving a resonant point of 6th, 7th, and 8th harmonic within amateur radio bands. Simple and effective. Oh, by the way,  I was not even born when this technique was published in many amateur radio publications. I simply love to implement known old techniques into new designs. It was published in Karl Rothammel’s antenna book, DM2ABK, Y21BK.

So, in the end, I am sometimes puzzled how HAMs tend to glorify some mediocre antenna designs but quick to dismiss good ones. I wonder what would be the next big mystery about the EFHW-8010 antenna. I guess it is time for a “Counterpoise” mystery. In the meantime ask yourself (and Google), does a resonant circuit such as half-wave resonator needs “extra circuit/counterpoise” to operate.

Stay tuned!

73 Danny Horvat, N4EXA aka E73M




Common Mode Filter Choke,RF Isolator,Line Isolator,Noise Suppressor-You name it!

As ARRL Antenna Handbook says:

” The common-mode filter or choke may be one of the best-kept secrets…  “


As this picture shows, common mode filters/chokes are widely used in industry. Almost every power supply and modern appliance has one. But we are here talking about the one we need in our HAM radio applications. Do we need one and why?

Apart usual reason, to stop your own radiated power coming down the shield of your coax into your equipment, I personally prefer use of Common Mode Choke as Noise suppressor. Ever since I read an article from W1HIS on chokes my main goal with them is to make my station reception clean. For sure it worked wonders at my contest station as well as at many others I helped with my products.

It is very much known about these properties of CMCs but HAMs rarely use them for these purposes. To  give you complete picture just read a quote from W1HIS paper:


In the HF hamshacks that I’ve visited, the background noise level heard on most HF bands (especially the low bands) could be reduced by more than an S-unit by means of common-mode choking.  In some cases (which I could name but won’t, to avoid embar­rassing my friends) I was able to reduce the received noise level by four or five S-units.  I reduced my own received noise level on the low bands by even more. For years I’ve been a regular participant in CW nets on the 80- and 40-m ham bands, and in SSB nets on MARS frequencies near these bands.  I hear better than anyone else in these nets.  I am often the only participant able to copy every one of the dozen or two dozen stations in a net.  Why can I hear so exceptionally well?  My receiver is nothing special, nor is my antenna; it’s a wire just 23 to 40 feet high.  Nor is my QTH very quiet.  I have a small lot in a dense suburb, just two miles from Cambridge and three miles from Boston I hear exceptionally well because I have good common-mode chokes in my antenna feedline, in the other cables connected to my radio, and also in the cables con­nected to the worst of the QRN sources in my house.


Well, I and thousands of other HAMs seen an improvement of their reception by using a Common Mode Filter / Choke in their feedlines.

73 Danny E73M / N4EXA

New line of RF / Noise suppressors / Common Mode Chokes

Recently  I have focused back to my experimental work on BALUN and Common Mode Chokes, also known as RF and Noise Suppressors. In past five years I have wound hundreds of Ferrite toroids and did countless measurements. I have learned a lot from various ferrite manufacturers as well as from some known amateur radio experts on this subject. My conclusion was that there is so much room for improvement in design of BALUNs and Chokes as well as broadband transformers. So, I set out to make better products compared to ones offered on the market which, by the way, after evaluation and measurements, in most cases  are pure “snake oil” or “Mighty Fine Junk”.

Average HAM or new comer in a hobby have no way to learn what is good or bad antenna product, it is up to these well established makers of the antenna products to set the bar for good or bad. Minority of us , which do know and understand the complex problems of antenna designs, do try to promote the knowledge and set things right but other then some forums and email reflectors there is no access to vast HAM community on this subject.

Over priced products, some times not working at all, only pushed me harder to work on properly designed and tested models. The results are amazing!

Not only that I validated the work of known experts on subject of Common Mode Currents and BALUN designs, I set the bar higher and designed some amazing products. Oh, do not think that I am selling a story, nicely packed in technical lingo, but in fact I am only one which has measured (precisely) and published a whole data on each product I design. Yes, there are some providing a basic data such as Common Mode Impedance Magnitude (Zmag) but nobody has produced a complete data of complex impedance to show a real picture of how the product works.

I have evaluated a products so badly designed that I could not comprehend how in a world they managed to screw the things so bad. Anybody knows how to buy a popular type of Ferrite toroid an wind a 7-12 turns and get average results. They failed to do even that. These guys are claiming a tens of thousands of Ohms of Common Mode Impedance while their product has less then 200 Ohms on some bands with only few Ohms of resistive part (Rs) and rest of it is reactive inductive(+/-jX). Some are claiming that their product works from 1-250 MHz  but in reality it works somewhere above 30MHz and not in any amateur band.  There are dozens of examples of these bad products, yet, they are being sold even by major amateur equipment distributors world wide. Well, it is not their fault, they just have no enough choice.

So, I have few more stuff coming but that is for another post, in the meantime explore a bit my products such as CMC-230-5K , a cascading chokes, which has dominant Resistive impedance from 2-30MHz.

Just to give you a hint, only Resistive part stops and Dissipate the Common mode currents and suppress the noise buildup on your cable by various sources for sure, reactive (inductive/Capacitive) part  of common Mode impedance can make things even worse.  On that subject some other time.

Stay tuned, more is to come….

Danny Horvat, E73M / N4EXA

NAVASSA-5 Antenna

It has been almost five years since first MY5T antenna was sold and tested in Germany back in 2010. Antenna was produced by me in Bosnia Herzegovina but due the lack of  building material  I have decided to move the MyAntennas back to USA. While I was figuring out how to make the antennas in my home state of Florida,  I was contacted by JKantennas LLC, an antenna producer in New York, and MY5T/My5F model has been licensed for production to this high quality manufacturer.  It was agreed to change the name of antenna to Navassa5 and to be distributed and sold exclusively by DXengineering.com

As I have no intention to produce such antennas at this time, my focus shifted to high quality antenna accessories such as BALUNs and Common Mode Filters etc.

  •   More info  about Navasa5 is available here  and VSWR charts are here.