Building a Half-Wave End-Fed Antenna For 6m, Part 1.
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- เผยแพร่เมื่อ 2 ต.ค. 2024
- Part 2: • Building a Half-Wave E...
Here I am building different impedance transformers to test on 50MHz using Alex VK2PRC's design and the classic 49:1 transformer. Cores tested are FT-140-43 and T106-2. The winner will earn a permanent spot mounted on my PRC-351 to use with a whip antenna.
Alex's video: • Video
Alex's 20m HWEF: • VK2PRC Half Wave End F...
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Interesting and educational video. You always have most informative videos and I enjoy them. Please keep them coming.
Thanks, will do!
Hi Gil, thanks for your videos! I built myself the EFHW with an FT114-61 core (2w:14w with a 68pF silver mica on the primary), used with a success on 10m and 6m (100W ssb). The SWR of the transformer (w/ the capacitor) itself is 1.3/18MHz, 1.0/21-28MHz, 1.3/50MHz here. The attached antenna wires cut into resonance do not change the SWRs. PS: no c/p used, a cap coupling via the coax works. Best 73 Igor de OM1ZZ
Great Video Gil.
The advantage of the halfwave end fed is that it does not require a ground plane and it has 3Db gain over a dipole. It also does not have the high radiation angle or multi lobes of the 5/8 or 3/4 wave antennas that still require a ground plane. Halfwave is very popular with wood sailboaters. Halfwave on a portable is a good choice.
Nice video Gil, cheers
Good job Gil. I have just started having a play with EFHW at HF using a 49:1 after extensive success with non-res EFLW and 9:1 with good tuner. Seen various rules of thumb for EFHW using 0.05 WL c/p which I guess can also be tagged to radio earth nut. Probably important QRO to avoid RFI bites. Low-ish power (say
All you need to know about efhw in single place
owenduffy.net/blog/?s=Efhw+transformer
SWR is not the only measure of efficiency, try to calculate the loss in the transformer.
15:09
vtenn.com/Blog/?p=1089
An EFHW is a full sized antenna but it's not a balanced antenna, like a dipole or a G5RV so that's where ( I believe ) the discussion about counterpoises comes from. Without a counterpoise, the shield of your coax will do the job of the counterpoise, but at QRP levels you probably won't notice that. Thanks for sharing the design for a 6m version, that would be great for portable use.
If it works ;-)
Hello Sir, Your videos are all very informative and interesting. I don`t use toroids for my end fed antennas as they can be very lossy at VHF without using special grades. Instead, I use a small coil and a preset capacitor arranged as a tank circuit with a tap a few turns up for the center of the coax. I have sent you an email, with diagrams and pictures, along with instructions. Just search for the word `coupler` on the subject line and you should find it. Very best regards from the UK. Hope to meet up on the air sometime!
Your videos are never too long, they're always too short!
Interesting expirement Gil, thanks for sharing. It will be interesting to see which transformer you decide on.
Hi Gil, for 6m the inductance is a bit high ... on 6m a jpole is handy ... if it must be a efhw Event. a fuchs-antenna (monoband) is a good alternative
73! DO2AK
On 50 MHz I would also try a J-pole Antenna with Koax. The Inductance ist to high. Very 73, Edwin DK2TY
The higher dip could be due to radiation from the feed line.
Without a counterpoise wire the coax feedline acts as the remainder of the antenna. What I hear people say is that because the EFHW is fed at a high impedance point the shield current is low and therefore not a problem. But this is not entirely true. The impedance at the feedpoint is high, so there the shield current on the coax is indeed low. But as you move further down the coax, towards 1/4 wave away from the feedpoint, the shield current gets higher, in the same way as the EFHW wire itself sees a higher current in the center (at 1/4 wave from the end).
When you like to add a CM choke in the feedline, the best way is to place it not at the 49:1 transformer but further down the coax where the impedance is lower and therefore the CM choke more effective.
Gil, You might want to check out the last video on the TRX Bench TH-cam channel. There he builds a matching tank circuit for the 6 m band without a using a torroid. Lots of math but informative. Cheers.
Will do, thanks!
@@RadioPrepper He also has an interesting series on the theory and building of CM chokes and baluns starting at video #100.
arkanızdaki 6 gen magneticloop icin bir video linki lutfen.
How about a J pole. It's a half wave with a quarter wave matching section. As for a counterpoise, Steve Elington on TH-cam has done a lot of work doing antenna current measurements with and without counterpoise, earthing etc with EFHW antennas. th-cam.com/video/MzfQybYMlUc/w-d-xo.html.
Also Sotabeams sell a Pico efhw kit and the web page explains that changing the toroid for a t50-10 type it will work on 6 metres.
Hi Gil
Your vids are always informative/educational/entertaining especially those on EFHW ants.
Because of my restricted environment, the EFHW has become my Go To Ant at my QTH bc it goes up/down with ease and keeps the Apartment Nazis at bay.
I'm very interested in 6M for both FM Repeater and SSB ops. Looking forward to your follow up vids on your 6M work.
My thoughts:
At 50 Mhz, vs 20Mhz, what are the magnetics/interwinding and compensation capacitances doing?
Also, would the Smith chart trace of a nanoVNA shed light on what a 3M bit of wire acts like with/without matching?
Your vids are quite valuable. I like/save each.
73 OM de KA1RUW
Probably, but I need to educate myself further to get to that level..
Hello Gil, thanks for all those DIY projects. Could you please share your toroid provider url ? I would like to build HWEF for the S-Pixie and the QCX. 40m and 20m.
73
It's Ebay!
top info video hammer cool top 73 de DE2TRF
Hi Gil, 73 PY2SNN Sebastião! Good job!
This is an alternative wire antenna. Not homebrew, but costs only 20 Euros. I have one. Drahtantenne für 6m Amateurfunk lambdahalbe.de/drahtantennen/6m-amateurfunk/index.html. Other wire monoband antennas from this guy have a slider on the matching stub (no transformer) for fine tuning the SWR. I don't hear much 6m activity, neither SSB nor FM, where I live. So the issue is only academic.
Nice thanks!
Must also add a comment on the link to VK2PRC - fantastic instructional video on the 49:1 balun tuned for 20 meters. Thank you for putting the link in, it transported me back to the days before antenna analysers and the guys who first introduced me to amateur radio. They were ex RAF and Royal Signals guys who really knew their stuff - it was like just yesterday and not 45 years ago. I've had to write to him and hope he picks up my email. 👍🏻👍🏻👍🏻 73 de M0AZE Mike
We all stand on the shoulders of giants...
17:37 Its interesting that some go with the 2 material and love it. Some go with the 31 43 and 61 material. The two auto tuners (that I have experience with, mfj and t-200) go with the 2 material . The differences are interesting and I can't say that I completely understand the differences. This is a very interesting video and the differences (which may be hard to measure) may be in the gain ? On to part two, and have you ever thought of perhaps a remote reading signal strength meter ? To show differences in signal strength ? I realize now this would be considered as an old video hah hah.
I have a field-strength meter now, but I used the FT-140-43 for something else...
Hi Gil, great video like always. But why not using a J-pole antenna? I don’t think you would try to use it as a multibandantenna, so there is no need for a probably on VHF lossy transformer.
Simply because I need a whip antenna for my military manpack and the J-pole while great wouldn't be as practical.
Radio Prepper You’re right, a J-pole would be about 4.5m long and not practical. I hope you will succeed to make a good transformer. I’m looking forward for part 2.
Radio Prepper use a plumbing union, maybe a few to shorten the J pole to fit into your pack
Fascinating stuff, I learned a lot and look forward to Part 2. Thanks.
Hi.
Czech military manpack radio Tesla RF10 had a nice wire end fed antenna, working in 50 MHz band. It had impedance transformer wound on small ferrite rod. Unfortunately, it was the qrp version. It should withstand 4W with the PRC351. I would not try to use it with the PRC352 amplifier.
73! SP6WJM
I have one! Unfortunately the radio does not work. I wish I could find another one.. I do have that antenna! Maybe I will try it with a PRC-351..
Thanks for the video Gil. One simple way to see if there is common mode current in the coax is simply touching it and/or moving it while looking at the VNA. If the curve changes just by touching or moving the coax you know you have common mode currents. From experience it’s almost always necessary to have a 1:1 balun / choke in almost any kind of antenna to eliminate cmc. In verticals with radials on the ground you can get away without it but .. losses..
Great info, thanks.
Hmmm an AR-6 Ringo vertical is an end fed half wave... yes/no/maybe????
It is a VERY popular antenna but seems to be unavailable from Cushcraft at this time. At about $130 US, many people are encouraged to try building something else especially since the Ringo cant be had now. I am researching efhw 6m verticals fed by a unun so I am here to watch your video to see your results about toroid core materials. Is a capacitor across the coaxial end necessary? 73 de w8nsi
ps: Okay 43 material for hf and 61 for vhf. No capacitor. Experiment time.
Great, sorry, I never heard of the Ringo.
Hope this link also gives some insight.
www.pi4vlb.nl/wp-content/uploads/2015/04/PA1SSB-Info-voor-het-maken-van-een-Monoband-en-multiband-end-fed-antenne.pdf
Is in dutch but think it will clear itself.
Lucht=air
Draad lengte = wire length
Aantal wikkelingen = number of wire turns (for the coil L)
Kern eg the toroid type if not air wound.
Tuning: mount a 3-3.3K resistor and tune with the rg58 (or alike) by cutting until close to swr.
If you might need to tune the antenna wire, just bend it back twisted.
Have a 20m version which works very well.
According to www.amidoncorp.com/ft-140-61/ it is the wrong material.
"61 Material and is designed for inductive applications up to 25 MHz"
What you need issomething like that T130-17
I think a well made Bazooka is the better antenna. Because it can handle more power output and has better bandwith. And there is no need for an transformer which produces a lot of losses and a lot of heat.
73´s DH1KJ
But I need a whip antenna on my military manpack...
Interesting stuff :-). Is the wattage that these are good for consistent if we always use 1mm wire ??
I would think so. A little bigger diameter for 240 size toroids probably..
Great experiments, Gil - thanks!
As always very cool video. Would love to see more about how the antenna wires are positioned during testing.
Just hanging... I will show more in the next video :-)
Just a suggestion: you might wish to keep a rubber mallet (with hard rubber head) in your Toyota for situations just like this wherein you drive a stake or an antenna mount into the ground. Very informative video. I have missed you on-line lately. It's that d@mned virus! 😒 AE5ZX
Gil thank you for the video ! Compare to à Dipôle ( 6m long!) without Transformer Why complícate the job with a EFHW for 50 MHz fréq. ?
A dipole for 6m is 3m long. As stated before, because I want a whip antenna on my military manpack.
Radio Prepper Ok cristal clearing, but in this case why not a 1/4 Wave vertical whip ?
thanks for your video... havent you tried using as a impedance transformer bifilar 300ohms wire the kind used many years ago for tv antenna? using that kind of a jpole... i have one that i use for 6m and it works great... you can even have it in doble half wave zepp to have more gain
Maybe I'll try thanks!
I am curious, did you do a followup video? I can't seem to find it.
Soon..
6m is so small.
Why not make a dipole?
No need for toroids or balun.
Because I need a whip antenna on my military manpack.
how abt a ef dipole kg6mn
Hey, I'm waiting for your sailing channel. How about an update?
Nice! Thank you for the educational video =) 73!
What type of resistor did you use to measure SWR?
Hi, carbon type, whatever I could find to amount to the correct value..
Merci Gil, j’ai hâte de voir la partie 2.
J'ai hâte de tester!
Yeah, what Denis said! Lmao
Ok. I know almost nothing about these type antennas.
What would happen if you run a Balun (1:1) after your transformer then to the coax to the antenna?
Antennas need some kind of counterpoise. An endfed use either the coax and/or metal support structures to distribute the missing half. In general it can be a noisy antenna due to using the outer of the feedline for RX & TX. I.E. it can pick up noise near the shack and radiate RF into the shack. I would definately make a groundplane for the antenna. It can be a quarter wave on the desired band. In this way you will radiate near the feedpoint, and you can use a choke or current balun, e.g. ferrite on coax near the feedpoint. Then you will have low common mode currents and least noise on RX.
The end-fed random wire yes, the end-fed half-wave not so much.
Toroids and transformers can have more losses on higher frequency. Complex permeability is a good hint here. One manufacturer recommended 61 material for 25MHz and below. Complex permeability means roughly that at some point inductance starts to behave more like a resistance. Then transformer will dissipate power. The higher the frequency, the smaller the inductance and more resistive it gets. This may not show up well on analyzer because a very small signal has very low magnetic field and losses increase a lot more with larger signal.
Material 43 is lossy at vhf too, even more than 61 probably. It is good material for chokes where resistive losses are ok or even wanted.
I'm not sure which material would be recommended for a transformer like that. Air cored would be the least lossy but they'd be very large at that low frequency.
73
-2 (iron powder) material has lower losses than ferrite materials at higher frequencies. For 50MHz it's a better choice than -61. The inductance per turn is certainly lower but that's fine, as you need less L at 50MHz anyway.
I'm curious to see how it works out in a real life test. Looking fwd to part 2.
I might try 6 material as well..
@@RadioPrepper Yes, also a good choice. -2 and -6 are not too far apart, with -6 for even higher frequencies. But the inductance of 2 or 6 are quite low. The T106 size has the highest inductance per turn (T80 or T130 are lower) but still quite low. You really need more than 2 turns primary. At 50MHz the ZL at 2 turns is only 16 Ohms. Which is in parallel with the 50 Ohm of the system. I would go for at least 5 turns (ZL = 90 Ohms). And a well tuned parallel cap to cancel out part of the L. Otherwise your transmitter will have a hard time driving this.
Do you know the website toroids dot info? See what happens if you fill in only one or two parameters, like # of turns and freq, then you see the impedance. Or frequency and impedance, to get # of turns.
I'll check it out thanks. I was going to use three turn primary, 21 total on the T106-2.
@@RadioPrepper Hmm, that would give you a primary of only 120nH (XL = 38 ohm @ 50MHz). With 82pF in parallel this might work.
Inspiring, thank you.
We'll see if it works...
I also found mono band end feds work better with 16 to 1 transformers. To get a rough idea of wire needed I divide 442 by the frequency to get feet needed and add a bit.
I bent the wire back and twist. Seems that if I cut the wire it is needed to be added later.
Only on 6m weirdly..
I was literally thinking about a 6m EFHW! Really, and not joking!!!
Great. I have to finish this asap!
Hi Gil, another great video, however, you lost me when you where talking about needing a transformer for a 1/2 wave antenna, I'm thinking something like this I bought from Amazon, www.amazon.com/gp/product/B07SSP7F7T/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 (I bought the 42" one) however, I don't see why you need the transformer. Can you please do another video where you explain this, or point me to one you have covered it before? Thanks
I wonder if there is any matching circuit at the base... It would be interesting to test the SWR..
@@RadioPrepper I'll test it in the next few days and post a url to the results.
That Tactical Antenna has a loading coil at the base.
You are right with a 1/2 wave dipole you do not need a matching transformer because you feed the coax to its center which is 50 Ohms Impedance, the 1/2 wave when fed at its end (EFHW) has a very high impedance 1000,s of Ohms, this is why the transformer is needed to bring the high Impedance down close to the 50 Ohms.
@@stevejones8665 Ah, got it now. The whole 1/2 wave threw me off, as I'm looking out at my CF 1/2 wave dipole, then turning an looking at my EFHW 2mtr antenna that is really 1/2 wave, with a loading coil on the bottom, and just SMH, saying to myself, "I know I'm not getting a really silly concept here"
I think those long HT antennas are a marketing gimmick counting on people's belief that longer is better. I suspect a high SWR and them counting on the radio's SWR protection circuit to kick in and reduce power to avoid drying the finals..
Great vid, as usual, missed you of late and I assume you’ve been busy. Thank you for the time, effort and editing to put these videos out on TH-cam for us to enjoy and learn from. 73 de M0AZE Mike 👍🏻👍🏻👍🏻
Much appreciated!
Hi Gill.. whats the velocity factor of that wire ? if it is steel it migh be quite high so your quater vave is going to be much shorter... I have also found some matching transformers have a natural resoant frequency.... try sweeping it unterminated
Thanks. Their site doesn't say, it's #534, 26g.
@@RadioPrepper Copper is going to have quite a high VF.. with the variation due to the insulation.... The steel I would expect to have higher resistance and therfore a low velocity factor. It could be as low as 50 in which case you are getting close to a wavelength... I have no idea how the copper and the skin affect afect the vf. It may end up the same as copper ??? It would be a good question to ask the wireman..I would love to find out. . It would also be good to know if there is a risk of it changing as you wind and unwind the antenna and potentialy crack the copper coating.. Have you considered feeding the antenna with a parallel tuned circuit ? This might be less "lossy" and you could make it adjustable in the field if you use an air spaced vareable capacitor.
I haven't tried since it works fine.. I suspect indeed that the VF would be much closer to copper...
Do I need a unun if I'm using a 1/2 wave or random wire just for receive? I'm using a sdr. Thx 73
th-cam.com/video/0zF7bDoqkG4/w-d-xo.html
To receive you don't have to but it helps...
Part: 2?
In the works yes...
Hi ~ what is the Gain of a EFHW ?
Slightly under that of a dipole.
Thnx
73 Gil , une petite réalisation bien sympathique , j'attend avec impatience la Partie 2 .
Nous verrons si ça marche!
Bonjour Radio Prepper, vos vidéos sont vraiment très intéressantes et éducatives, malheureusement mon anglais laisse vraiment a désirer et la traduction Google pas tjrs au top surtout avec des termes techniques.
La bonne idée, je sais que cela vous donnera beaucoup de travaille en supplément, serait de toutes les refaire en français, voir avec une voix Off
En espérant que mon idée retienne votre attention, merci et continuer à nous faire rêver
JP
J'en fais en Français mais malheureusement je n'ai pas le temps de les faire toutes..
@@RadioPrepper merci
Je me contenterai des vidéo en français
Merci pour votre réponse
Comme d'habitude Gil, tres bon mon ami.
Merci!
Excellent.....waiting for final result.
There might be more contenders too...
73' 51' 10:20 où trouver ce piquet support de mat ??
Sporting goods store, fishing aisle..
Bonjour Gil, je vous ai envoyé un petit mail afin de m'éclairer sur la bidouille d'une antenne, vous semblez être un chef dans ce domaine !!
Bonjour. Dès mon retour le 20...
What is the conversion from centimeters to inches and feet
You actually see end fed half wave antennas on VHF and UHF all the time. On cars and on repeaters. I don't know the details of how they match them.
Thanks, I'll look into that..