EFHW Antenna VS Dipole - Field Strength Measured.
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- เผยแพร่เมื่อ 28 พ.ค. 2017
- Comparison between the EFHW and Dipole on 20 meters. Center support is a fiberglass mast. Test shows field strengths are identical.
Note: The swr on the EFHW was about 1.2:1, a bit higher than the dipole however it remained the same across the entire 20m band whereas the dipole was quiet narrow. This shows one more advantage of the EFHW. 73 - วิทยาศาสตร์และเทคโนโลยี
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Thanks for your clear, straightforward videos, Steve. It's really helpful for those of us who are new to antenna construction and design.
Amazing that the end fed and the dipole are performing the same! Thanks for the video! ;)
Just what a needed to know. I worked out that they should be the same, but seeing it actually demonstrated and with such care is perfect. Thank you for your thorough test
I know you made this a long time ago, but I just ran across it so it's new to me. Nice work, and thanks for taking the time to do this! I'm not sure you could have made it a more even, fair, real-world comparison.
Excellent test Steve, often wanted to try this comparison. Great video.
Nice video Steve. It should not surprise anyone familiar with the theory of EFHW antennas, but it is valuable to see it confirmed practically.
Thanks Steve for taking the time to A/B an end-fed dipole! XYL k6sew and I are going full-time RV'ing and I'm counting on an end-fed dipole for hf operation along with my Buddipole Vertical. 73/k6sdw
Thanks so much for doing this, I just posted a question in the efhw group and them came here and see you information...
Thanks for making and sharing this video Steve. Cheers and 73! de W3LAM
That Corsair II looks like a lovely radio!
Very well done technical comparison, congratulations!!l
I was just watching some other video these days and realized I should build a simple field strength meter to use for tests. Thank you for sharing this. I always thought a dipole is a bit better. In my location building a dipole is hard so EFHW is for me )). Now I stay relaxed as it doesn't seem to be any diferenfe. 73
Thanks for the video. Very nice QTH you have there.
EFHWs are my favorite QRP portable antennas and I never use a counterpoise with them. What little coax is used provides all the counterpoise needed. Fast and easy to setup and tear down, and they perform great. N6ALT
correctly, you should place a line isolator as close as possible to the UNUN to suppress the sheath currents and the resulting RFI interference, such an antenna then, instead of transmitting into a coaxial cable, requires a counterweight in the length of lambda 0.01-0.1. The ideal situation is when you are able to supply the EFHW with an appropriate counterweight in the form of an earthing system, but if this is not possible, a version with a counterweight is offered. Only such use is a correct understanding of the principle of operation on which this antenna is based.
Very good comparison indeed, End Fed Antennas work well in my very small garden, Far better than Dipoles ! Thanks mate 😀
Very nice video. I am a bit surprised. Thanks.
Great comparison . Thanks .
A neat test !!!
Nice. Thanks for your time.
Excellent job! Thank you. 73, K1RCE
Nice. Very helpful. Have found my efhw to be valuable with all the bands that I can use. Performance seems the same, though sometimes I wonder if it doesn’t quite hear as well. Maybe it is just me😀
Very helpful. Thanks very much.
I've never use a counterpoise on a end feed antenna and have QRP DXCC.
They are my main antenna both from the condo and in my ops from the national forest twice every month.
Lee, WA8QFE
btw, TNX for the HW9 rear panel, 72 es 73.
appreciate the video Steve, thanks ! 73 de M1ELB
Yes, several have complained about the "near field" signal but don't understand the whole point of this test.
Modeling software indicates that on the antenna's fundamental freq. the radiation patter is exactly the same no matter where it is fed therefore far field results don't reveal anything. All I was doing was demonstrating the efficiency of the transformer and feed system so wherever I go with another receiver won't matter. Besides, 10 wavelengths would put me in the neighbor's yard a block away. I've moved 40 miles away now so don't expect me to put this thing back up for another test just to prove the same thing over again.
My main antenna presently is a 80m horizontal loop at 100 ft high fed with home brew 600 ohm line. Works fine on all bands.
Very helpful thanks Steve sounds like you got some nice exercise too all that too and fro old mate. Never ever thought to set a distance transceiver as the field strength meter. I have considered trying some similar experiments walking in a distant circle with my small cw qrp rig and the cw beacon running on the antenna test rig at low power. need a big paddock for that job tho. Cheers from vk5cz ..
A Hallicrafters S76 with its giant meter would work nicely!
Interesting results. Nice video.
I made pretty much the same type of test comparing an OCF40 to my home brew EF40. The only difference is I used reverse
beacon.
KU3X
Yep, well its the same antenna fed at two different points. Interesting point that the end-fed configuration is more usable on other bands..
Good to know ! Thanks 73 de ve3hip in welland Ontario Canada 🇨🇦
I wonder if it is picking up any signal from the coax or just the antenna.
Good, now I know I'll be getting an efhw.
Hi Steve. I'm new to HF, and have been perseverating for a couple of weeks, as the snow slowly melts up here in Minnesota, over choosing and setting up a backyard QRP antenna to drive with my newly built qrp-labs 20 amd 40m QCX's. I've been bouncing back and forth between various antenna options on the qrpguys' website, and after much indecision I finally sprung for their multi-Z tuner with the idea that I could try different antenna configurations. Your video has given me excellent answers to most of my questions. Better still, with the multi-Z I can even replicate your experiment. Thank you for "making it real" for me.
I do have three related questions left, though, if you'll be kind enough to help me out. I hope the answers will help others:
1, Is there anything special about the 1/4-wave height of the center point of the inverted V, or does it just make a nice inverted V with end points on the fence at about 5 ft-ish high?
2. Would the radiation pattern be flatter if the whole thing were mounted higher? and
3. Would the radiation be improved in dipole configuration if it were fully horizontal? The reason for this last question is that I happen to have three trees in a straight line each 30 feet from the other, which would be a very convenient "tower system" for a 20m dipole.
Thanks again, and 73.
Julian, N4JO.
1. Radiation pattern is dependent on antenna height. At 1/4 wavelength high, the takeoff angle is high, 90 degrees being the peak. This is very bad for 20m but good for regional work on 80 and 40 meters. A 20m antenna should be 1/2 wavelength high or higher for decent DX performance.
2. Not necessarily improved but certainly different. The inverted vee is more omni directional than the dipole thus a slight loss of gain.
You would be better off with a true EFHW instead of a random length wire and that tuner since the EFHW is resonant and has less ground loss.
@@n4lq In that case I'll do a resonant half wave in the back yard and save the tuner for when I'm out exploring on the motorbike, and need to tune a random wire. Right now my goal is just to to get something out there so I can listen to some real CW while I try to learn it. A half wavelength at 20m is still over 30 feet, and I don't think I can get that height for a dipole, so it'll have to be a sloper or an inverted vee like you show in your video.
The impedance at the feedpoint is also lower for < 1/2 wavelength, isnt' it? Should one make any corrections for that, or doesn't it matter too much?
Thanks for the advice!
Thanks for the great video and for hustling in the heat. I'm rather late to the party concerning end fed antenna configuration. I have a Myantennas 80-10 and my shack is on the second floor with a feedline exiting at about 18 feet off the ground. I have a shack ground wire running from the shack floor inside the exterior wall to an 8 foot grounding rod. My plan has been to position the transformer box at 18 feet and run the antenna wire 130 feet through my trees. Do you think, if I ground the coax shielding to my ground wire this antenna will perform properly? I realize this isn't the typical deployment. Thanks for your thoughts, Steve KZ5MSE.
Your installation is very common. I have a friend with a similar one. That ground wire is only helpful for lightning protection. As far as RF is concerned, it's just another antenna and a rather long one at that. in fact it's 1/4 wavelength on 20 meters and will radiate like crazy if allowed to. So what you should do is install a common mode choke .05 wavelength from the transformer along the coax feeder. Preferably the section of coax between the transformer and choke should be outside if possible.
You are much better off building your own choke vs. buying one. Most store bought chokes are not adequate for what we need. This is simple. Just order 2 or 3 cores. These should be FT240 ferrite which are about 2.5" in diameter and 31 mix. Wind RG8x or RG58 around them as many turns as you can. You can put them in series along the coax. These will have an amazing effect on RFI and noise pickup. See K9YC for more detail. k9yc.com/2018Cookbook.pdf
Commercial chokes are very expensive and have tiny cores. DIY 73
@@n4lq Thanks so much Steve; I've watched your videos for years and have Finally subscribed. Much of your stuff has been over my head, but I'm catching up. ...For some reason I ordered a CMC 130S common mode choke along with the 80-10 endfed from Myantennas. I'm guessing that choke should do the job. Thanks again for your answer. Stay safe!
Excellent test. Before I pick one of these up, I will be using about 20 ft of 8x to the radio. Should I choke the coax at all? Or just make sure it's grounded
A ground connection at the box is best. Choke is optional if needed but not likely if the ground is decent.
@@n4lq Hi Steve, I just use a FT240-31 toroid core with 14 turns of coax as a choke and it's located 8 feet from the feedpoint on my 40 meter EFHW antenna (I'm basically using the first 8 feet of coax coming down from the feedpoint as the counterpoise). This works great and eliminates the need for a ground connection. Using the choke works especially well for portable operation as it's just part of the feedline but it's also what I do at my home QTH. The choke also works great for minimizing common mode noise on the feedline.
@@wd8dsb Indeed however you should ground the coax before it enters the shack anyway. This provides a DC path to earth for some protection.
Thanks!! Very good job! The one thing however they keep adressing in my area is that the EFHW is noisier than a dipole. Did you ever measure that difference ?
73, PA8M (Wim).
Usually noise pickup is due to installing the antenna too close to the house or noise pickup by the coax shield feeding back up to the antenna. This will be true of any antenna but many EFHW's are installed poorly because of lack of room. The antenna cannot tell noise from desired signal. If it's RF and it passes through the wire then it will be received.
I wonder what the bandwidth of the EFHW is compared to the dipole? More bandwidth also means more noise is hitting your radio’s receiver. A high q narrow bandwidth antenna acts like a preselector filter which rejects noise that is near to the edges of the bandwidth of the antenna.
Steve - do you have a nanoVNA to measure the bandwidth of each configuration?
Hi Wim, I've been testing my new 40 meter home brew EFHW antenna mounted 20 feet up in the air. My home brew transformer has a pretty high efficiency of slightly above 90% (tested using 100 watts). I'm using the first 8 feet of coax running vertically down from the transformer as the counterpoise, and then I have 14 turns of the coax wrapped on a FT240-31 toroid core as a choke. The antenna feedpoint is mounted 20 feet from my house. I have to say my EFHW antenna is definitely not noisy. During mid day my noise level is less than S1 on 40 meters on my old TS-180s. As others have mentioned people that complain their EFHW antenna is noisy probably have their antenna mounted too close to their house and/or are not using a choke on the coax which would allow common mode noise on the feedline to get back to the feedpoint of the antenna making their receive noisy. The choke also does a great job preventing RF on the outside of the feedline from getting into the shack. I highly recommend using a choke on the feedline similar to what I have done to make the EFHW system a very repeatable system. Without the choke I can see the SWR vary when I touch the feedline, but this does not happen when the choke is used. I'm very impressed with my 40 meter EFHW antenna.
Methinks the only real difference , you sort of glossed over is that with the dipole you did not have ( nor need ) any form of ground / counterpoise. With the EFHW, you had an 8' ground rod. Well that's a heck of a counterpoise and not one easily come by when packing. I'd be VERY interested in the exact same comparison, but this time done with a 14' ( your dipole leg length ) wire counterpoise just laying on the ground [ perhaps testing twice - once parallel to the antenna and once at 90 degrees to the antenna ]. A final test could be with no counterpoise / ground at all. Thanks for the video and for allowing my two cents. K7AOZ
Good point. I have already tested this and I can disconnect the ground wire to the rod and nothing changes one bit. It would make a difference if my coax was only a few feet long but with 75 feet laying on the ground the rod is mainly just for lightning protection and static discharge.
I routinely use an ef-40/20 with no ground or counterpoise. The coax is only about 3' or less. It generally slopes at 45 degrees or so up into a tree. This is my picnic table setup. I never felt any kind of disadvantage not using a ground or counterpoise. I rarely interfere with another KX3 set up at the same table when the antennas are positioned properly.
My assumption has been that while it is not a balanced antenna it is still a 1/2 wave antenna and therefore doesn't really need any kind of RF ground (I'm not talking lightning protection). Is this a bad assumption?
If the antenna were not cut for 40 meters (stub for 20 meters) - if it were a random wire - then I would definitely be using some sort of ground or counterpoise.
Always enjoy your videos Steve. They give me plenty to think about.
73 Kev K4VD
Thanks
I think a 3rd test of giving the same output to a Dummy load and checking FS would have confirmed that actually it's the antenna field strength you are measuring, and not something else (Feeder radiation, LOS). Please try that too.. nice attempt.
Isn’t this test for “near field” only? I don’t have a problem with the test and use end feds but just wonder how effective the difference might be 100 or 1000 miles away.
Use Reverse Beacon for that test.
Super work
But why antena is must?
Antena is a cable
But work is great.
Have a nice day for you.
I wish you had tuned to 10 meters and tried the same test. According to another of your videos the angle of radiation is lower using the End Fed method than the Dipole method. Thus the Field Strength meter should be slightly higher feeding the antenna End Fed. Any chance you could try this ? Thanks for your experimenting and videos !
That was about a year ago but yes, your're right about the patterns being different so it is difficult to reach any conclusion other than that there are no big power losses between the 2 feed types. 73
Have you ever made any EFHW transformers or played around with random length 9:1 ? What do you think about them ? 73’s
Hi Steve, nice test, but for my understanding, if you set the minimum RF-Gain from your TRX to S-7, than it can't get lower then S-7?
Best 74
Martin
That would be true on the typical JA rig but on the TenTec, the RF gain acts as a shunt. The lower you set it, the more signal is shunted to ground thus it will appear weaker. The meter will still respond normally no matter where you set the RFG but just not as high if it's turned down. The JA rigs control the RF gain by applying a fixed value of AGC voltage to the RF and IF stages thus acting similar to a squelch whereby the signal must reach a certain level before the meter will move.
Dear Stevie, thanks for answer and clearing that out. Well, I only have JA transcievers, thats the reason why a was asking. Like to see more test of your nice "end fed antenna system" Best regards from Bavaria as Mark
Also, the IC-7300 using the "shunt" method to reduce RF gain like the old TenTecs do. I have one here and when you reduce the RFG the meter still just goes toward zero instead of slamming to the right.
am commenting on this YT 6 yrs after this was posted,
I think it would be better if you did the test at a minimum of 10 wavelengths away and not right on top of the radiating antenna.
Been operating 10 through 20 meters these past months now that we are approaching the next sunspot peak,
noting I hear very few end fed antennas on the higher frequencies, which tells me that they may tune up and have a decent SWR, but that does not necessarily mean they have a decent low radiation angle which is so important for 14-30 MHz. (on 40 and 80 meters they are a great antenna for domestic work) ...
I run semi low power here 50 watts, and use a 40 meter delta loop, which performs OK on the harmonically related bands, 20,15 and 10 meters, the lobes have gain on the higher frequencies and at low radiation angle, the drawback is that the peak radiation pattern lobes are in terms of azimuth, and if the "DX station" is in that low angle Lobe, I can usually make the contact, if not then I don't work them (and most likely dont hear them very well.
One other comment is that having been through 6 sunspot peaks and chasing DX on the higher frequencies, I surely find this time around that there is now what seems to be a lot of "big gun/high power" stations out there.
Quite often they are running 1 KW or more, so if you are running 100 watts or less you're already at a disadvantage by almost 2 S units.
Bottom line for 10-20 meters concentrate on antennas that radiate at a low angle, ie, a 5/8 wave vertical.
My 10 cents...
Tip for the unwary: whilst this antenna type is probably OK, a true vertical anywhere near a wire fence is going to be untuned to a high degree.
You camera warps space :)
No surprise that the same piece of wire in the same place works the same. The main reason for poor performance of end-feds is lossy step-up transformers, which your evidently is not.
Nice Corsair 2
I understand a half wave ant can be fed at any point end or centre or even off centre and in theory perform similar. And as you say it might be advantage to feed at one end for convenience. However I have tried many times half wave end feeds with little success, probably user error but not because they don't work , they do ,but rx noise is always much worse than a well balanced centre fed , preferably a doublet with open wire that can also work on harmonics. So for me a true test is not only how well a ant tx but rx is even more important. Hope I am making sense .
There is no technical logic to the theory claiming the position of the feed point determines the amount of "noise". If "noise" is experienced then one needs to investigate and locate the source of the alleged "noise" and decide why one antenna can hear the "noise" and the other one cannot.
Let's say the "noise" is coming from Jupiter. The superior antenna can receive it and the inferior one cannot. Should we declare the superior antenna "NOISY"?
If the feed line happens to be running near a noise source , be it coax or ladder line, either type will develop common mode current on either the shield of the coax or the ladder line. These currents do not cancel on the ladder line because they are in phase thus the term "common mode". Either type of feed line can transport the noise into the receiver unless steps have been taken to mitigate it. With a coaxial cable fed dipole we put the common mode choke directly at the antenna's center feed point. This isolates the outer shield from the inner shield and prevents egress. We may also need a CMC at the receiver to further isolate this shield.
For "balanced" feeder, which is seldom actually balanced, there is no shield and the noise is fed to the shack's matching system. We can't put a choke around the ladder line so we need to convert it to an unbalanced system using either an antenna tuner of some kind and or a balun. After this we can attempt to choke the shield before it enters the receiver.
I have verified many times that the reason people experience noise pickup from their house wiring or cable TV is due to their feed line running near the source or the antenna actually crossing over the house. The end fed antennas get the blame because the antenna's feed point is often near the house, even under the eave or even laying on the roof. This is how reputations get started and it's a shame. Install a center fed dipole in the same manner and you would get similar results
As for Common Mode Chokes. With the EFHW we have determined that one should be installed .05 wavelengths (lowest band) from the transformer using a high impedance choke. This will provide the necessary return current for the transformer plus isolate the remaining coax from it. Please watch my video on how to construct one.
th-cam.com/video/UP6G7PYyZHg/w-d-xo.html
As for feeding a multi-band antenna with ladder line..... Just keep in mind that the impedance of a center fed half wave antenna will vary as the frequency is changed. While being as low as 25 ohms on the design frequency, depending upon height, it will be 5000 ohms on the harmonic. These wild excursions stress the feed line to the max and thus we need to use air insulated, widely spaced, open feeders to prevent excessive power loss. Then the antenna tuner is also pushed to it's limit attempting to match such a beast and losses can be quiet high.
With the EFHW, the end of the antenna will always have a high impedance on both the design and the harmonics. It will always be in the range of 1500 to about 3500 ohms. Compared with center feeding, the ratio of impedance change is much lower, 2:1 in this example while center feed will be 25:5000 or 200 to 1. The EFHW negates the need for super low loss open wire feed and presents a workable match to the 50 ohm coax by stepping down the end impedance by a 50:1 ratio.
The EFHW also has the advantage of being at DC ground potential via the transformer's winding. This provides a path for static electrical charges to bleed off and a degree of lightning protection if properly grounded.
73 N4LQ
@@n4lq Thanks for your comprehensive reply . I am in no doubt what you say is all true , and my amateur knowhow is limited as I said 'user error ' . I am more of a try this and see if it works type . And I have put some effort into end fed and travelling wire and half wave end feds all with limited success. Yet I can make a doublet out of speaker wire and T-rex tape (see my latest version video, don't laugh to much ,hi )and they just work every time with low noise and good results. I live in a rural area in Scotland with my nearest neighbour 400metres from me ,I have done a experiment with a top band doublet in my field and a 86metre sky loop nither you could describe as noisy but doublet wins in rx and sky loop wins 90% tx, any end fed never made it to to field , again that might all be down to user error, I know many hams have great success with them . Maybe I am just a center fed ham fan ? I am not hating on your experiments, I think you are doing a great job . Very 73 Rob MM0UDI.
@@robduncan599 Hi Rob, I use a home brew 40 meter EFHW antenna mounted 20 feet above ground and I use a choke on the feedline 8 feet from the feedpoint, and my EFHW antenna is very quiet. On 40 meters my S meter is S1 during mid day. My feedpoint is 20 feet away from my house. I measured my home brew 64 to 1 transformer efficiency at slightly greater than 90 percent using 100 watts. I really believe if you use a good choke on the feedline similar to what I have done you will find the EFHW antenna to not be any noisier than a dipole mounted in the same location.
@@wd8dsb ok tks for your input . I might give it another go ? My radio activity is casual user ,I am not a DX'er or contester . My current ant is 240 feet doublet at 15 metre ,10 metre vert , I plan a 40 vert gp, my double is a fabulous all round ant . I am a big doubt fan ,but like experimenting, so might give EFHW another go . 73 MM0UDI.
it looks like you should be experimenting with a half-wavelength wire, not the length of the λ / 4 wire in the 20-meter band as you did it, btw EFHW , 73
No... It was 1/2 wavelength
@@n4lq OK , Sorry my mistake hi , all the best
Yeah but that is nearfield radiation. How about farfield?
Same antenna, different feedpoint. Radiation near or far will be the same assuming equal efficiency if measured on the fundamental frequency. Farfield vs nearfield has nothing to do with this.
Please never use that camera stabilization again. It's nausea inducing.
wimp
@@n4lq I am just trying to help you. lol
What it means is nothing. You're not measuring the near field. Bad science, bad test. Very flawed. However I appreciate your attempt and enthusiasm, but totally futile.
I was beyond the near field, one wavelength. Also it doesn't matter for this test since we were just looking for efficiency, not pattern Billy Bob.
@@n4lq I guess my point is, no matter what antenna you connected, your results would have been similar. And pattern is very important if you're trying to compare efficiency. You have too many variables and unknowns, thereby rendering your results and conclusions worthless. Again, I appreciate your attempt but don't draw any concrete conclusions based on that experiment. Good for you for trying none the less. 73
The stations you’e trying to reach are not in the near field! For my portable antenna setups there are so many less than ideal variables the difference is probably negligible. This test is probably as detailed and relevant as an amateur needs as it reasonably indicates a faraway station will probably notice little to any difference in the readability of your signal coming from either antenna.