An Interesting, New Fan Dipole Technique (

[@JosephVE3GKT]

A fan EFHW will not work with a <a href="#" class="seekto" data-time="2941">49:1</a> if you want to use it as a resonant antenna. A <a href="#" class="seekto" data-time="2941">49:1</a> is matched to a high impedance wire to get 50 ohms. If you attach a second wire for, say band B, that is not a multiple of a half wave on band A, it will present a lower impedance than the first wire on band A, and will give high SWR at the feedpoint. So a 20m wire, for 40m EFHW, will work. When you attach a 10m wire next to it, for a 20m EFHW, or a 15m ish wire for 30m EFHW, either of the shorter wires will be lower impedance, and mess up the SWR. This is why fan antennas (fan dipoles and fan verticals, like a DX Commander) are fed at the low impedance point of the radiator wire 73 de VE3GKT

[@ddaddybass]

So my 10m wire has a different impedance than my 20m wire?

[@peterk.824]

Exactly! Last time I checked current flows the way of the lowest resistance… in this setup the right wire will always have the highest impedance… basically you will always have a terrible mismatch

[@gwss01]

@@peterk.824 Agree. EFHW for 80m is hi impedance at 80m but not at other frequencies. EFHW for 40m is hi at 40m but not at other frequencies. Connect the two antennas in parallel (a fan arrangement) and most of the power fed to it will go into the wrong antenna. Overall impedance will always be low. 49:1 balun is there to drop a high impedance antenna down to 50 ohm coax. If fan is giving 16 ohms (perhaps), balun converts to about 0.3 ohm. The mismatch of that to 50 ohm coax is terrible. A regular fan dipole works because the resonant antenna is a low impedance and the other wires are non resonant so have a high impedance. Put them in parallel and power goes into the resonant wire and stays out of the non-resonant (reactive, high impedance) ones.

[@larrysclassroom2118]

@@gwss01Correct, a friend of my tried adding a second element in fan configuration and it reacted exactly as you described, messed it all up. He quickly removed the additional element.

[@cwebs1000]

Back in the late 1970s I made a "fan" dipole using Slinky's for the 40 meter and slinky Jr.s for the 20 meters. No balun just 6 winding for a choke. Worked Japan on one watt CW. The slinky Jr's were stretched out 90 * to the big slinky like inverted V. Installed in attic. Just collect coils with close pins to tune. I put an SO239 at the antenna and used SWR meter right at the antenna to tune Worked great for me. AB1ZI

[@danielsteele7544]

Thankyou David,what a blessing u are to us who are learning .The Lord bless you and keep you.

[@rickeaston3228]

The problem with most new antenna inventions is that they are not based upon some antenna engineering principle, but based upon intuition and guess work. There are simple designs to make simple uncomplicated antennas but people seem to have to reinvent the wheel and try to replace it using something that is not useful at all beyond what we have now.

[@dougtaylor7724]

Many want to use the Feng Shui method for design. LOL

[@JxH]

Inventions are almost always based on intuition and guess work, but that intuition and guess work itself needs to be built upon engineering principles if it's to have much chance of success. Inventions (at least the interesting ones) rarely flow in a linear-thinking way directly from engineering principles. Optimizations can be churned-out by robots, but usually not inventions. Inventions are described as "novel" for a reason, and the reward of a patent monopoly period is a reward for the creative thinking. It's actually funny when Corporations try to systematize the creation of solutions, as if (present day) robots could crank the invention handle. But yes, inventions need to ultimately be based on engineering principles, but via well-informed 'intuition and guesswork'.

[@n4lq]

NO IT WON"T WORK AT ALL. .... Just a few inches of another wire attached to the feed point will skew the SWR ( a lot). Just getting your finger near the terminal will also. Stick a long length of wire on the terminal and you no longer have an EFHW. This idea gets reinvented about once per week. Shucks....All you need to do is try it. You'll quickly find out how to ruin a good multiband antenna. Also the <a href="#" class="seekto" data-time="2941">49:1</a> is not a balun. It's a transformer. Also a counterpoise is NOT to be used. If you do insist on using one, avoid a length that is any multiple of a wavelength otherwise it will radiate as well or maybe even better than the antenna! The whole point of the EFHW is multiband capability without any counterpoise. The coax shield supplies the tiny bit of displacement current needed to satisfy Kirchoff's law. Adding radials or long counterpoise won't accomplish much. A ground point either at the transformer or along the coax give you some lightning protection but doesn't make the antenna radiate any better.

[@BusDriverRFI]

You didn't even mention that he had the 30m stretch longer than the 40m stretch.

[@kevingary7018]

I have an 80/10 meter half wave end fed dipole antenna in my back yard. It is resonate on the lower portion of the 80 meter band, but due to the harmonic properties of the antenna , it is also resonates on other bands. I only need one wire for a multiple number of bands - how cool can it get - the magic of harmonics.

[@K6TJO]

Isn’t the Efhw antenna with <a href="#" class="seekto" data-time="2941">49:1</a> transformer measured to the lowest band you wish to operate naturally resonate on higher bands??

[@alv6530]

Ok, thanks for the input. it was just a thought trying to overcome the space limitations I have on my lot. I was just wondering why a reflector/counter cut for the lowest frequency on a quarter wave dipole couldn't act as the reflector for all of the frequencies.

[@areyoucrazyoo]

Small space on your lot, look at the DXCommander Classic It's a 1/4 resonant Fan Vertical.

[@alanb76]

Dipoles without baluns allow noise from the house wiring to conduct into the receiver. With many station setups there is noise that can degrade reception this way. You can also measure transmitted RF getting onto the outside of the coax and on to the equipment chassis if you don't use an effective balun. This can lead to hot mic and hot key situations, even to the transmitter locking on. Antenna system design should strive to keep the RF on the antenna and not allow it to get on the outside of the coax or the station chassis. The (choking) balun's purpose is to keep the RF where it belongs which makes both the receiver and transmitter work better. These effects are frequency sensitive so it might seem to work without a balun on one frequency and turn into a problem on another. Measurements of RF current on the outside of the coax are a good way to check.

[@TheNoCodeTech]

I read about this a time ago

[@Eweyouhew]

80 meter End Fed Dipole with the choke ~10 feet from the balun is broad banded already. Several bands included already. Just one element with no Counter Poise

[@johndrees830]

Dave given that an end fed half wave dipole is resonate at both even and odd multiples of a half wavelength, would not the 80 m half wave EFD interfere with the 40 and 20 and 15 and 10 meters? I wouldn’t see why you would do a fan anyway since EFD is multi band . Fans are for center fed dipoles but I agree with your <a href="#" class="seekto" data-time="2941">49:1</a> transformer/balun

[@JxH]

What many are missing is the following: 1) Low impedance antennas (e.g. 1/4-wavelength) can conceptually be connected in parallel because the elements naturally go *up* in impedance when not resonant. So the current tends to be self-selecting and naturally flows into the lowest impedance element, which is the desired resonant element offering the lowest impedance. 2) In contrast, End-fed half-wave are high impedance at the feed point. So simply paralleling them means that the unwanted elements are likely to be lower impedance and the current will naturally flow into the "wrong" element. Mr. Kirchhoff doesn't know that your feed point node was intended to be high impedance. The self-selection in example 1 (above) works against you when attempting to parallel EFHW. Clearly it's a complete mess trying to parallel EFHW elements. To be clear, this is merely the first layer, and there may be more complex interactions. But it *is* the starting point, so everything else would build upon it.

[@richegan7381]

I may be wrong, but an end-fed half-wave length of wire is not a dipole…correct? Isn’t a dipole two quarter-wave lengths of wire ? Why do folks keep calling an EFHW antenna a dipole? -KA2VCW

[@DaDitDa]

An EFHW is a dipole at its fundamental resonant frequency, but multipole at its higher harmonic resonant frequencies. A dipole antenna can be fed at its center, off-center and end. Ken WA8FCI

[@RealMesaMike]

@@DaDitDa No it's not a dipole. It's a half wave monopole. "Dipole" implies two poles of opposite polarity.

[@DaDitDa]

@@RealMesaMike On its fundamental resonant frequency an EFHW -- like all half-wave antennas -- is a dipole. The position at which one feeds a half-wave antenna does not change the fact that a half-wave antenna is a dipole. An example of a monopole antenna is a quarter-wave vertical antenna with a ground-level counterpoise which is effectively a half-wave antenna with one-quarter of its electrical length being the ground-level counterpoise. Regardless, the radiating element of a quarter-wave vertical antenna is the physical and electrical monopole vertical element. Recall that the "pole" being discussed here is not a physical pole or structure. It refers to the number of voltage poles that exist on an antenna at its fundamental resonant frequency. An EFHW at its fundamental resonant frequency has two voltage poles of opposite polarity; i.e., it's a dipole antenna. Ken WA8FCI

[@Clark-N1NVK]

At my old house I built a typical 15' NVIS for 75 & 40 M but not as a square, as a HEX with 20 M added, and level instead of sloped. In retrospect I should have raised 20M to 20' to get it above 1/4 wave. ... next time. N1NVK

[@A___Way]

Excelent Ideos. Im thinking of making a dipole from 2 adjustable multiband verticals. My question is how important is the matching between the two sides? They are different models

[@BusDriverRFI]

The antenna has a resistance, an inductance and a capacitance value. By combining two quarterwaves into a half wave multiband dipole setup, they will interact with each other. If there are levers to pull to adjust the antenna elements, even if only on one side, you should be able to make it resonant. With that being said, ideally you would have the antenna elements in a horizontal configuration at one half wavelength in height above ground. In the vertical configuration, height is not so important. But then you may as well use them as quarter wave verticals. Hmmm.

[@ddaddybass]

I asked a very similar question on FB today with various responses. I have a QRPguys no tune EFHW and I’m curious if it’s possible to to run this a vertical (fanned dipole style) like a dx commander. I’m I wrong thinking the signal will seek out the appropriate length element in an EFHW? I know spacing of the elements are important. TIA

[@g0fvt]

The DXCommander uses 1/4 waves which are low impedance, and are also low impedance at the third harmonic. the largest currents will be in the correct elements. Perfectly sound science, a fan of end fed half wave elements will not behave in a similar fashion.

[@g0fvt]

It seems a strange idea TBH, if he operates on 80m for instance the 40m leg will become a 1/4 wave and low Z. A conventional fan dipole is a more attractive proposition or even an EFHW cut for the lowest band. Of course at high power an end fed still needs a significant amount of current to go somewhere, the best part of 1a at 1500w....

[@eureoma578]

its called a fendfed antenna

[@NoMoreUsersAvailible]

I think N6MTS (@smittyhalibut) talked about this on the Ham Radio Workbench podcast. IIRC, apparently the EFHW won't work because the resonant frequency isn't the lowest impedance the way it is for a dipole or a vertical.

[@olivierconet7995]

This EFHW fan grives me an idea: setting a normal EFHW, that will resonate at harmonics, 40m, 20m, 15m, 10m Then adding EFHW elements for missing bands (30m...) I will try that. Thanks for the idea F1SOC

[@BusDriverRFI]

Multi band multi band element high impedance feedpoint antennas can be simulated on simulation software. Try it there first. You may find a lot of crosstalk between the elements anyway. The reason traditional fan dipoles work is because the feedpoint impedance is low. This means the undesired elements do little to nothing. When you fan out high impedance elements, the undesired elements begin to resonate taking your resonance out of band. But by all means, give it a try.

[@paulshaffer9674]

I call them Porcupine Dipole. I had a good one half off the top of my flat roof. Mine was for 10, 12, and 17 meters.

[@RealMesaMike]

EFHWs are not "dipoles" They are half wave monopoles.

[@DaDitDa]

It would be helpful to explain your claim that the EFHW antenna is monopole. In other words, how is an EFHW different from all other half-wave antennas that are known to be dipole antennas.

[@dj6orandrew915]

They are not monopoles necessarily. An EFHW cut for 40m will also work on 20m and 10m assuming a 49:1 transformer.

[@RealMesaMike]

@@dj6orandrew915 Sure, but that's irrelevant to whether it's a dipole or a monopole.

[@RealMesaMike]

@@DaDitDa A dipole has 2 active elements fed in opposite phases. Now, maybe you can call it a dipole if you consider the second element to actually be there, but of zero length. But, an end-fed wire doesn't seem to meet the definition of a dipole, if you ask me.

[@DaDitDa]

@@RealMesaMike I think you're conflating physical with electrical characteristics. For antennas, a dipole refers to existence of two (di) opposite polarity voltage poles. All non-traveling wave, half-wave antennas operating at their fundamental resonant frequency exhibit two voltage poles -- they are all dipole antennas regardless of the physical position of their feed point. Ken WA8FCI

[@extreme978]

End fed dipole?? Should call it end fed DUMMY LOAD!! Point Blank: The best dipole antenna is an inverted "V" Get the apex as high as you can get it. 45 to 50 ft is good, then 10 ft off the ground on each end. With an inverted V, I can give someone the same signal report with 100 watts as they can with 800, on some of those silly antenna designs. Im not trashing you Dave, But I have tried every antenna in the arrl antenna books, and nothing works like an inverted V. Im just worried that some of these antennas could confuse newbies and discourage them. 73, & 99

[@Calico5string1962]

Sooooo... pretty much, you have no idea...? LOL

[@redddraggon]

That's not going to work

[@BusDriverRFI]

Some people don't understand the issues with high impedance. Low impedance is lossy, but you can do things with it that you can't do on high impedance designs.

[@JT-py9lv]

Send me one. I'll test it for you :-)