All About End Fed Antennas, Field Day Educational Activity - Ham Radio Q&A

Joe, KD9CJX and Jerry W9GLG give a presentation on end fed antennas at the Wisconsin Valley Radio Association's 2021 ARRL Field Day. This was the group's educational activity for Field Day.
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Timestamp
00:00 Introduction
01:25 What is an end fed antenna
05:02 Why end fed antennas require impedance matching
07:40 Half Wave End Fed Antennas
08:12 Random wire end fed antennas
09:58 Advantages of random wire end fed antennas
11:05 Are counterpoises necessary?
13:47 Describing the matching transformer (UNUN) for a random wire antenna
15:43 Wire length's importance to a random wire antenna
17:03 Efficiency can be affected with wire length vs transformer size
18:50 Combating coaxial radiation (ugly baluns or chokes)
20:41 Questions
25:23 Ending
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#EndFedAntenna #EFHW #FD2021 #ARRLFieldDay #Antennas #TechnicalDiscussion #Hamradio #amateurradio

[@kevingary7018]

:) ... I put up an 80/10 end fed half wave with lots of dog legs to fit in my small back yard. It is a forgiving antenna, and exceeds my expectations.

[@johnjanoscrat8000]

Thanks, Mike, Joe, and Jerry. As a 70 yr old (only an operator for 6 years), I'm a big fan of EFHW. I have a 102 foot sloper, and a 132 foot in a inverted V configuration. Your video taught me a a lot this evening. And Mike, the 2 meter J-Pole you sold me a few years ago is still performing superbly. 73s "The JJ" KC3EWY

[@wayneskiba1237]

Great discussion on end fed wire antennas, this is the only antenna I use at my home qth for simplicity and ease of installation, and on occasion portable, great job, Michael!

[@GraemeKoch]

Thanks Michael, I have been using an end fed random wire now for about 8 years with great success. Thanks for the video. 73, VK3GEK

[@alex-ks2se]

I haven't gotten a ham license, know very very little about ham in general, and am mainly interested in learning for emergency situations. The information in this video is priceless. Thank you for sharing!

[@bassangler73]

You should at least get your technician ticket, it's a fairly easy test to pass..things don't get really technical until the general test which I am currently studying for...You might as well get licensed it would be nice to get another person on the air!

[@NoName-ou3pl]

well, I took some notes and surely will try a few ideas. Thanks for explaining it so clearly ! !

[@chrismosquad1056]

Excellent video! Thanks for making it, guys! Very much appreciated!

[@luisg6000]

Amazing …. The very best EFHW Antenna explanation I have ever seen!!! Thank you very much 👏

[@JB-do5qd]

Thank you for all the information, what a great exchange with regards to End Fed, & Di Pole antennas! Impedance & Practical use of Wire, Frequency, Measurement & Voltage! Stellar discussion! = ]

[@NickKemp897]

This video helped me make sense of dipole and end fed antennas more than any other resource. It was something about the content or sequence of the content that made it click for me. As far as I'm concerned, antennas are magic juju and this video dispelled some of that. Thanks for helping.

[@kb0roc]

awesome! finally understood EFHA , long wire , etc

[@jefft2553]

Thank you very much for posting this training/class. It wasbvery helpful and I appreciate it.

[@radiomen123]

This video was really good for me and clarified a few questions. Good Job!!!

[@kingdnh]

Great stuff. Learned a bunch.

[@banjomandan7199]

Thank you! I learned a ton! Encouraged now that I can put up something decent on my small lot.

[@sphexes]

Nice gravel bike Michael! I love my endfed!

[@usernamemykel]

Great stuff, thanks Mike!

[@Capt_Duffy]

Great presentation 👍👍👍

[@drewt.4353]

Thanks for clearing that up. Half or random.

[@okhamradio]

Thanks for sharing this really interesting information

[@davidhilton7780]

Wow I learned something, thanks!

[@John-K6RXD]

Excellent Thanks.

[@pratwurschtgulasch6662]

one thing the first presenter needs to realize that an antenna creates a circuit and as such there is a return path. He thinks you can just connect the center of the coax and leave the shield unconnected, but the shield is the return path and the antenna forms a capacitor back to the shield through the air. This field contributes to the radiation (it's not just the current which is also what he said), so the shape of this field affects the radiation of the antenna, so it's not something that should be ignored.

[@W1ZY]

Another way of understanding what's happening along the horizontal wire is as follows. *Ohm's Law* We all remember Ohm's law. Resistance voltage and current are related to one another. If we know two of them, we can calculate the third. In this case, we want to understand the resistance along the horizontal wire because we are trying to understand why the impedance rises towards the ends of the wire. So that would be: *R - E/I* *Resistance (or impedance) = Volts/Amps* The resistance (impedance) is lowest in the middle of the 1/2-wave wire-- about 50 to 70 Ohms. As we progress away from the middle, the impedance (R) goes up. This is because when we pump power into the antenna, it is equally distributed across the wire, _but in varying proportions of Voltage and Current._ So let's say we pump 100 Watts into the wire. At the center that 100 Watts will be comprised of, say, 100 Amps and 1 Volt. At the ends, it may be comprised of 100 Volts and 1 Amp. Since the Current/Voltage ratio varies as we move across the wire, its impedance (or resistance) varies across the wire. This is because the resistance (impedance) along the wire _is Ohm's law, which says the resistance is the ratio of the Voltage to the Current (R=E/I)._ In the middle, we hypothesized the 100 Watts was comprised of 100 Amps and 1 Volt. In Ohm's law, that would be 1/100 or .01 Ohm. At the ends we hypothesized the 100 Watts was 100 Volts and 1 Amp. Ohm's law says that is 100/1 = 100 Ohms. What that shows us is that where the Voltage is maximum, the resistance is maximum. And where the Voltage is minimum, the resistance is minimum. In this hypothetical case, by a factor of about 1000. *Current Feeding vs Voltage Feeding* So as you move your feedpoint across the wire, the Voltage/Current ratio changes which changes the aerial's feedpoint impedance. If the wire is at least 1/2-wavelength long, *the maximum impedance will be at the ends and its minimum at its center **_no matter the frequency you operate it on._* You can expect to see the same high impedance at its ends on all bands. You can take that to the bank--which is exactly what the manufacturers of the "end-fed Hi-Z matching transformers" are doing. They know that the ends of a wire will show about 5000 Ohms no matter the excitation frequency. SO they make a broadband transformer designed to match that predictable Hi-Z to 50 Ohms. The takeaway is that when you excite the wire at the end you are _Voltage Feeding_ the aerial. When you excite it at the center, you are _Current Feeding_ the antenna. *Current Radiates the RF Signal* The only other tidbit to add is that an antenna has maximum current at its center and minimum current at its ends. And it is the current, and not the voltage, component that causes an antenna to radiate your signal. Therefore the middle of the antenna, where there is maximum current and minimum voltage, is its "Filet Mignon" section. It is the part of the antenna that radiates most of the signal. Therefore, if you do not have enough space to hang a horizontal wire, you try to get the Filet Mignon middle part up as high as you can, and then do what is necessary to its ends in order to make it fot -- e.g. drop the ends of the wires vertically towards the ground if you do not have sufficient room to span its entire length.

[@W1ZY]

*RF GROUND Necessary for Voltage Fed Antennas* A little confusion about "counterpoises". When you _Voltage Feed_ an end fed antenna via a ferrite transformer, it is best to do it at ground level. That is where you mount your commercial "transformer box. From the box's "hot" lead, you run a wire up to the horizontal part of the antenna--the vertical part becomes part of the antenna's total length. You then connect the coax to the transformer box on the ground. The "cold" lead from the box goes to a ground rod only 2 or 3 feet long sunk into the earth. Off the ground rod, you run several "counterpoise" wires several feet long, arranged, if possible, in a wagon wheel pattern. The purpose of this is to create a good RF GROUND to act as a "counterpoise" to the matching transformer in your box. The old fashioned way of thinking about this is that the RF GROUND "gives the transmitter something to push against" when pumping electrons into the wire. If you want, you can add a current choke balun made from turns of coax around a PVC tube, a dozen ferrite beds slipped along the coax, or a 1:1 current balun (not voltage balun) before the coax run back to the shack. You do not want to use the coax feedline as the counterpoise. You do not want to run a long ground wire from an elevated transformer box to the ground. You want to feed the end fed on the ground via a vertical wire up to the horizontal run of its length, and put a short ground rod with several short wires coming off of it on the surface of the ground, or buried in the soil.

[@TwoFeatherChannel]

very interesting

[@briantrask8173]

I was wondering if you could run a random wire using 450 ohm ladder line straight to a balanced tuner?

[@pmull252]

What is the performance difference between using an end fed half wave vs a quarter wave end fed.? I bought an end fed antenna recently which is 41 foot long. This would be roughly a quarter wave at 40 meters, which is the band I want to use. Will it make a big difference if i increased the size to around 66 foot which is then a half wave for the 40 meter band? Thanks

[@jerryuhte1284]

Sorry i was having a hearing problem , you are correct at 50 /70 Ohms !

[@Dennis-sb7gp]

Good show. I'm getting a random wire when I move 9:1

[@danev1969]

Thanks from a new HAM. 73, KJ7YBK

[@briansalsbery9968]

“SWR is not resonance” Great point!

[@brentjohnson6654]

Very good video. Interesting … I am considering end fed antennas for portable and learning how to feed them and hoist them up. I plan on starting with Shark Ham Sticks based on your recommendation. I am also wanting to try end fed antennas mounted on a trailer hitch mount. Where can I learn about lengths of random wire trade-offs? All the best, 73 de KI5HXM

[@richarde735]

@20:30 you want the choke as close to the antenna feed point, yet others (waters & stanton for example) say to have it close to the shack. so which is it?

[@KB9VBRAntennas]

There seem to be two contradicting thoughts on this. Left unchoked, your feedline becomes part of the antenna system and will act as a counterpoise. Some people believe that you should then use a common mode choke at the feed point to prevent that from happening. Others believe that you should let the feed line radiate and place a common mode choke near the transmitter to keep RF 'out of the shack.' I haven't seen a consensus that one method is better than the other. My recommendation is to use a method that works best for your installation as environmental factors will affect the antenna system's performance. If your coax feed is relatively short, say less than 50 feet, I'd probably choke at the feedpoint. If your coax is 75 feet or more, then I'd be more likely to let it act as a counterpoise as the chances of RF making it into the shack are greatly reduced.

[@frankwc0o]

One other interesting fact about EFHW, is the height of the antenna. You gain more dBs if your transformer is high off the ground compared to a slopper.

[@eknaap8800]

A 'sloppy' antenna does not work well. A sloping one works just fine...

[@usernamemykel]

@@eknaap8800 It depends whether or not he is using his tongue.

[@Ben--David]

I use a full wave 20M End Fed. VSWR 1.0:1 across the entire band.

[@pratwurschtgulasch6662]

since you build antennas i'd really like to hear your thoughts on this buddy.

[@MrTonyd1954]

Does the arrl books on antennas cover these topics in case you want to read on this subject matter?

[@Gordofor12]

In great depth...

[@daveN2MXX]

14:25 the 3 wires don't have to be wrapped 9 times around the torroid for a 9:1 transformer....the 9:1 ratio comes from the 3 wires ie 3 squared is 9. You can wrap the 3 wires 2 times or 100 times...it would still be a 9:1 RF transformer.

[@KB9VBRAntennas]

You are correct, thanks for the clarification

[@ekiskaliburnirvana9047]

So how can we determine the number of turns

[@forgetyourlife]

I knew that notebook was there for a reason. ;)

[@eddy4011]

Greetings could you tell me what gain have the EFHW antenna. Excellent your video

[@KB9VBRAntennas]

Gain can be difficult to ascertain with HF antennas because mounting height can affect the take-off angles and radiation patterns. Also multi band antennas will have major and minor lobes when you move off the fundamental frequency. For the most part a 40 meter EFHW should have about 6 dBi of gain at its fundamental frequency. Here's a page that has some interesting plots to help more with this concept: www.qsl.net/kk4obi/EFHW%20Straight.html

[@eddy4011]

Thanks Mike excellent answer to given you master, it was a doubt that I had was to know more less and thank you very much for the reference link 73 W4EDY

[@larryak0z672]

My EFHW acts like it is shorted. No noise on receive and high SWR. When I unscrew the shield from the pl259 and only the center is hooked to the so239 I get receive noise. What would cause this? Thanks for this great video!

[@KB9VBRAntennas]

Maybe the capacitor went bad, or there could be short circuit in the winding.

[@larryak0z672]

@@KB9VBRAntennas Well, I finally found the problem. Bending the coax at the pl259 connector a certain way caused it to short. These were factory connections. I hate these types of problems.

[@KB9VBRAntennas]

Of course, always check the connections first. Glad you found the issue.

[@turtlecreek4633]

Joe, loved the presentation. I enjoy your approach. Do you have any extra class study/training videos from the club? Asking for a friend ;) 73 W3RRM

[@Gordofor12]

Unfortunately no, I usually do the classes in person.

[@turtlecreek4633]

@@Gordofor12 keep it up, they are lucky to have you. Thx 73 w3rrm

[@johnwest7993]

The guy doing the presentation doesn't seem to realize that the frequency doubling for ham bands started essentially at 160 meters, then 80 meters, and not at 40 meters, then 20 meters.

[@RobertMacCready]

I'm leaning on the Palomar Engineering antenna. Not so good with the homemade stuff and I like the company. Video was enlightening but somewhat confusing. If you "show" the actual antenna, put it together, stick it up in a tree, connect it to your radio, make the choke and put it in line, and make some contacts...now we're talk'in!

[@americaswayout4489]

Search for EFHW on Facebook you may find the 12,000 posts on this subject? Steve Ellington has some youtube videos covering his years of experience with the 49/1 version.

[@KB9VBRAntennas]

You are correct, but Facebook has a terrible search feature and a low signal to noise ratio. You may spend more time digging through the chaff to find good bits of info.

[@americaswayout4489]

@@KB9VBRAntennas Steve Ellington on youtube has a complete presentation, with a compensation coil to use 75 SSB plus the capacitors to lower the resonance point on the higher band. He is the Facebook poster and has spent years finding the better approach to 49/1 transformer use.

[@JayN4GO]

I don’t necessarily agree with the efficiency of a random ef being better than a properly made efhw. Grounded while using a choke or line isolator should be at the entrance of the home. You will find if you choke a efhw at the feedpoint , you will have about 2 ft of rf radiating. N4LQ has many proven studies of the end fed antennas. I like to say my 9:1 unbalanced random wire acts like a dx commander vertical while my efhw acts as 3 resonant dipoles. Inverted V config of course. Rf does act strange with + 90 degree bends. Build a delta loop and watch the radiation pattern on whisper. 👍🏼

[@wd8dsb]

Hi Jay, I actually recommend you place a good RF choke on the coax about 0.05 wavelengths from the EFHW transformer on the lowest band of operation, and then you can eliminate the separate counterpoise wire. The shield of the coax between the EFHW transformer and the choke becomes the counterpoise. The 0.05 wavelength recommendation comes from the work done by AA5TB as well as the 4NEC2 modeling that I did to understand his recommendation. On my 40 meter EFHW antenna my choke is actually 0.06 wavelengths from the transformer. During comparison tests of a 40 meter dipole mounted 20 feet up and my 40 meter EFHW mounted 20 feet up I can't detect a difference except for stations right off the ends of each antenna (each antenna compass heading about 45 degrees different from each other during the test). I should also mention that my EFHW transformer efficiency is 90.6 percent which is a loss of only 0.43 dB which is less than 0.1 S units. You can read some other comments about this in my response to another comment up above. 73, Don (wd8dsb)

[@larrybarnette4795]

Yes, I picked up on that blank statement that "a random wire is more efficient than an end-fed halfwave." It certainly accurate to say that a random wire that is properly matched to your radio and feadline will be more efficient than an improperly matched end fed antenna, but there are too many variables to make a blank statement. This includes it's surroundings, it's proximity to absorbing objects, ground conductivity angle of wire to ground, and other variables. Either can be a good radiator when properly matched. Also the choice of the best material for the matching network (usually a torroidal transformer) can make or break an installations efficiency. If you can match it at the antenna before it hits the coax, feedline losses are reduced. In a random wire installations, there is almost always a reactance to be tuned out at the radio end. This further adds to loss in the coaxial line over one that is matched at the antenna feedpoint. A halfwave end fed matched at the antenna would not add this additional feedline loss due to high reactance having to be nulled out at the radio-tuner end.

[@g90tech-x1c]

It's interesting how much discussion the EFHW generates. Every opinion from soup to nuts. I have an opinion, but it's not important. What is important is that you give one a try and form your own opinion. 73!

[@tomcook5813]

Could I use a resistor at input to bring impedance down?

[@KB9VBRAntennas]

Resistors can be used at the ends of antennas to tame impedance and help them perform on multiple bands. My recent video on the Chameleon Tactical Dipole 2.0 uses that concept. But you lose a bit of power due to the resistor efficiency. I suppose you could also put a resistor in parallel at the feed point to bring the impedance down, but this would be a highly inefficient method of transforming the impedance.

[@warplanner8852]

I'd add to KB9VBR's comment that, iyou could just use a 50 ohm resistor and eliminate the antenna entirely.

[@pratwurschtgulasch6662]

at 23:54 somebody asks if they can do a u-turn on the wire if they don't have enough space, so it can still be tuned. The one guy says that once you wrap it 180 degrees RF won't be able to come around that bend. That is totally not true. Maybe if you're in the GHz. The real reason why this would not be good (at least I think) is because the currents would cancel out in this portion and basically defeat the purpose.

[@pratwurschtgulasch6662]

maybe i should think of this as a meandered antenna

[@bigdaadio.K2WW]

It has nothing to do with "electricity turning corners" but running the element close to itself, CLOSELY SPACED.

[@pratwurschtgulasch6662]

@@bigdaadio.K2WW Right. If they are closely spaced, the coupling is so strong that it might as well just be one wire; but you ham people use such low frequencies that I'm not familiar with.

[@DK5ONV]

Why 64:1? A 49.1 is way fine to go with! Just saying...thx for another informative documentary video. Happy weekend to everyone out there / in here. 73's from the German Fontier de Your Friend Uncle Guenter

[@wd8dsb]

Hi Guenter. Either will typically work just fine and no one ever mentions it, but a 56.25 to 1 might be the best compromise if you're not sure if you want to use 49:1 or 64:1 (example: 2 turns on the primary and 15 turns on the secondary theoretically yields 56.25 to 1 which puts you right between 49:1 and 64:1). The feedpoint impedance of the EFHW antenna like all other antennas is dependent on how high the antenna is mounted above ground, and therefore there really is no one perfect ratio to use and that's why some folks use 49:1 and others use 64:1 (depending on the installation one might provide a slightly better match than the other). Just FYI, and 73 Don (wd8dsb)

[@DK5ONV]

@@wd8dsb Hello Don, thx for coming back to message. Yes right, all this makes sense what you mentioned. The Height from the Ground makes it happen or not. I run a home made 49:1 Transformer Balun + an Extension Coil 34µH. The feeding point is mostly very low..like 12-15inches from the Ground, vetical polarization as a portable setup. But this antenna works just so fine and is simple to install for a one man army in just no time. It weights nothing and doesn't ask for much of room in my back pack or RF Utility Baggage. Keep up good work & happy weekend from the German Frontier, sincerely your Friend Uncle Guenter

[@wd8dsb]

@@DK5ONV Hi Guenter, the EFHW really is a nice antenna when properly implemented. I also saw some data from W8JI that shows the feedpoint impedance of the EFHW is lower when operating it on the harmonic bands, so if you use the EFHW on the harmonic bands a 49:1 might be a better choice than a 64:1 transformer. As an example the 64:1 transformer might be a better pick if just using a 40 meter EFHW on the fundamental band (40 meters in this example) but if you intend to use it on the harmonic bands then the 49:1 transformer might be the best pick based on the W8JI data. Again, no right answer as it all depends on mounting height and if your operating the EFHW antenna on the fundamental or harmonic bands. Just FYI, Don (wd8dsb)

[@pratwurschtgulasch6662]

the other thing both these guys need to realize, it's not all about matching impedance, i can use a 50 ohm resistor as an antenna, perfect impedance match but doesn't radiate. When they are talking about the random wire, what are the constraints? Is 1 inch a random wire? It's not 1/2 wavelength so according to these guys a 1" random wire will work great provided the impedance is matched... nope.

[@bassangler73]

I think you are stretching things a little...lol

[@jerryuhte1284]

Center of the dipole is around 70 Ohms / not 200 !

[@Gordofor12]

A off-center fed dipole is 200. A regular dipole is 50-72 depending on if it's hung as a flat top or inverted V

[@TheNoCodeTech]

Hey, I know that guy sitting in the chair.

[@clems6989]

Would be good video if you could see the board...

[@usernamemykel]

But I DID see the board - maybe you need eyeglasses.

[@kingduckford]

I"m lazy, I'll just keep using center fed. Makes things stupid simple, easy and no problems.

[@pratwurschtgulasch6662]

the all about end fed antennas educational video says that electricity doesn't like to go around corners LOL

[@thomasmaughan4798]

Seems to be somewhat of a fad antenna. While he is sort of correct (and sometimes rather incorrect, I see the other guy trying to correct him a few times), he assumes rather a lot on the part of the listeners who might run home, connect just the center of a coax to a half wave antenna (how long is that, exactly?) and if such person is lucky NOT destroy his radio or get an RF burn as the "counterpoise" IS his feedline and human body at the south end of it. Emphasis on OPEN circuit at the end of a coax; IF the coax is 1/4 wavelength (mind the velocity factor!) it will transform open to short; thus open circuit at the antenna will reflect as a short circuit at the radio. But since some energy is radiating at the feed point, you won't reflect it back as a short circuit and if you are incredibly lucky it might even be around 50 ohms; but you are going to have RF along the entire length of the *outside* of the coax. How did it get there? Well, the entire INSIDE of the coax is a CAPACITOR with reference to the inner conductor. So you charge this capacitor on the positive cycle, it has nowhere to go since y'all decided to NOT connect the feed point shield to anything, so the coax shield itself becomes a radiator.

[@Midwest-FieldOps]

15:25

[@brian.7966]

great stuff, please move that guy standing to your right.

[@thomasmaughan4798]

End fed and random wire are NOt two separate things; end fed is a *special case* of random wire. As you tune the frequencies, your radom wire will BECOME an "end fed half wave" when the frequency you have chosen just happens to be a half wave. But it did not suddenly cease being a random wire. Maybe a Random Lucky Wire. Well, Random Unlucky Wire since it is difficult to feed a end-fed halfwave antenna.

[@rickeaston3228]

Does this guy think I can read the board,LOL.

[@MrDirkhead]

must be annoying others talking when you are explaining how antennas work. You would think they would move away, it's quite ignorant.

[@paulbyrne3328]

Sounds like someone is talking in the background. Thought it took away from a good presentation.

[@davewhite7679]

I think what you were hearing was the gas powered electric generator in the background. KZ9V

[@KB9VBRAntennas]

This was recorded at Field Day so there was a bit of background noise, including the generator. Not the perfect environment for recording a presentation.

[@Gordofor12]

And rain....lots and lots of rain.

[@richlovin2173]

Not too useful. Could not see his drawings.

[@michaelpoczynek]

I did find this interesting. Thank you very much for sharing this with us, it was quite informative. Have a great day. DE VY2MJ 73 😀