As expected 2017 was another record year at Myantennas.com with thousands of products shipped to 106 DXCC countries all over the world. Our products are becoming very popular among HAMs with great positive reviews resulting in growing demand for EFHW antennas and CMC’s as our bestsellers.
This morning on January 2nd, 2018 we were surprised with another cold day in Florida with temperatures plunging down to 5 deg. Celsius forcing our “Santa” mailman to wear the cap and fleece while picking up the “presents” accumulated over the new years weekend.
I wish you all Happy New Year
Danny Horvat, E73M, President Euroxpress corporation
The MEF-107-2k+ is new high power EFHW antenna transformer(~50:1 ratio) designed with massive 1.25 pound (0.57kg) ferrite core, equivalent of almost six (6) 2.4-inch toroids and very low insertion loss for frequencies from 1-7MHz
Insertion loss measurement S21 with two back to back transformers shows only 0.18dB (4% power loss) at 160m and 0.28dB (6% power loss) on 40m bands.
The FD 2017 is just around the corner. During the Field Day, 2016 many used our popular EFHW-8010 and EFH-4010 models and reported excellent results. This year we added many products to our website including installation plates (pole, tower etc.) for our EFHW-1K version as well as EFHW-HP version. Recently we added a transformer MEF-330-HP (used in EFHW-8010-HP and 4010-HP models) as a separate item for those who want to build their custom EFHW antennas 75m or use at the MARS frequencies etc.
Some of you expressed the need for thicker 14ga wire more suitable for harsh environments with snow and sleet. We added also our standard 18ga wires for those who often tie the wire to moving trees and forgot to leave some slack. Anyway, they are all available at our “Accessories” section, see the link below.
It has been just little over two years since MyAntennas.com started its production operation in Florida. Being avid contester and DX-er I wondered how many countries (DXCC) we ship our products to in these two years. Well, with the recent addition of Barbados (8P) we placed a pin #97 at our DXCC world map. See the image bellow.
After few beta testers, we started building and selling two new transformers capable of 2kW ICAS.
The new transformers MEF-330-2K (3-30MHZ) and MEF-310-2K (3-10Mhz) are the product of the constant search for best designs in order to satisfy the need of some users wanting a reliable EFHW antennas capable of withstanding the longer periods of transmission with high power without overheating the transformer which results in a change of Ferrite material.
It is known that every RF broadband transformer has insertion loss which converts to heat into ferrite core which after reaching its curie temperature (not saturation) changes the properties of transformation ratio and results in elevation of SWR of the antenna.
These two new transformers use ferrite material with higher curie temperature and larger cores in order to dissipate the heat easier than smaller transformer like MEF-330-1K (1kW ICAS version).
Results are great, MEF-310-2K has an only 0.14dB loss on 80 and 40m while MEF-330-2K average the loss of 0.55-0.6dB from 3-30Mhz.
New antenna model, EFHW-8010-2K is already in production and will satisfy many users wanting to use them in CW/Phone “rag chewing” style of operation as well as DXpedition and contest style of operation.
The new duo-band model EFHW-7540-2K will come out soon with unique feature covering the 75m (3.8MHz) and 40m (7-7.3MHz) bands without use of traps and only 110ft long. It will satisfy many users wanting to have single wire antenna capable of legal power on phone part (75m) as well as the whole 40m band with low SWR.
It has been a long search for suitable materials and quite a few experimenting has been done to design a high ratio (~50:1) transformer for EFHW antennas capable of high power (1500W ICAS). In the same time, it was hard to cover the wide range of HF spectrum from 3-30Mhz, yet I did it again!
I am proud to announce that new transformer MEF-330-HP is almost double in size of its little brother MEF-330-1K and also has a bit less insertion loss on all frequencies between 3 and 30MHz. A new transformer will be incorporated into new/old EFHW antenna models EFHW-8010-HP and EFHW-4010-HP as well it will be sold separately for those who want to make their antennas for use out of HAM frequencies for their needs such as MARS, Marine or EMCOM activities.
I have been writing about great results I and many others had with the use of CMC- Common Mode Chokes as noise reducers when inserted in your coaxial lines. Many CMC’s have been sold by MyAntennas.com and many positive reports came from happy customers. Please see the great video report by AC0HF who demonstrated reduction of noise averaging a 3S-units (18dB).
We have received reports from few with results of 5 S-units (30dB) and more of reduction of noise.
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 ultimate MAGIC antenna!
There is no BIG secret about EFHW-8010 antenna, it is just wide band low loss transformer and a piece of wire. Yes, there is a coil at few feet from the box but it is NOT TRAP, it is not 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 half wave radiator with a variation of Tesla transformer almost 88 years ago in 1928.
Various versions of End Fed Half Wave-EFHW dipole antennas ( some with a very high matching loss) were introduced by radio amateurs in last 80 years including mine with best-designed broadband transformer and “Compensating” coil. This small coil is almost invisible at 80 and 40m bands but due its position and value makes a nice impact on current distribution on high bands.
For example, an EFHW-8010 antenna is half wave resonant on 3.6MHz, its fundamental 8th harmonic is 28.8MHz but due Velocity of wave propagation on copper wire (with insulation), real 8th harmonic is above 28.8MHz. same applies at 7th harmonic at 25.2Mhz and 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.
So, at 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 EFHW-8010 antenna. I guess it is time for “Counterpoise” mystery. In the meantime ask yourself (and Google), does resonant circuit such as half wave resonator needs “extra circuit/counterpoise” to operate.
” 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.
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.
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.
Emil, E71A a world know contester ordered custom made 15m monoband antenna.MY515 features 5 elements on 9 meters boom optimized for maximum gain and low VSWR across the band. I named it MY515 since the boom is a bit longer then standard W2PV design I converted into MPV5 design antennas as made for my contest location, see it here: http://www.e73m.com/MPV5.php