#344

Today's video features the ARRL EFHW Antenna Kit by HFKits.com, which is essentially a nice, weatherized 49:1 UNUN Transformer to convert the 2500-3000 ohm end-fed halfwave feedpoint impedance down to approximately 50 ohms. I review how to build/assemble the unit, and run a quick bench test.
The kit is available from the ARRL as well as HFKits. Here are a few links:
ARRL:
Sale page:
www.arrl.org/shop/End-Fed-Half...
Instructions:
www.arrl.org/end-fed-half-wave...
HFKits.com pages:
www.hfkits.com/build-instruct...
www.hfkits.com/product/end-fe...

[@bradbuck7891]

Bravo! Short video packed with relevant information without a bunch of nervous “uhs” and “ums”!

[@AlvinMcManus]

My kit just came today. It will be my first build as a ham. Thanks for the clear instructions. 👍👍

[@hamtrucker]

KK4LGL here I am just getting into building antennas. I see why the old guys say make your own. It really does help you to understand and become a better operator, especially a QRP operator.

[@barrykery1175]

That is a well designed kit. Even the mounting bracket for the core was thought out. I just checked their web page and they really have a lot of good information on their page. Great video, thanks for posting. Barry, KU3X

[@b33v3n0m]

Nice video. I just happened to look at the ARRL kit this morning and then I saw your video after watching something totally unrelated. Very nicely done, and for the price it would make a great second (or portable) antenna.

[@Wb8wfk]

I built one in the summer of 2021 and it works real good. Made good contacts using QRP 5 watts

[@t1d100]

Thanks for sharing. Not my area of interest, or expertise, but it is always fun to watch a build. Tip = You can g-r-e-a-t-l-y strengthen the anchor bolt point by just adding a backer plate. A large flat fender washer can work. Add a little epoxy under it. HTH.

[@kao354]

Looks good! Now we'll wait for real usage of this UnUn for an EFHW.

[@vincei4252]

Very nice! Happy Holidays, Alan. 73

[@johnbrandolini2915]

Great video! I bought one of these kits a while back because where we live we don't have room for a proper antenna. The kit has yet to be built since I had some questions about winding the toroid. Watching you wind the xfmr cleared them up. Thanks. de N1ABE 73>>

[@steinshaw2490]

Thanks for another great video. And thanks for sweeping all the bands as it answered a question I have. I had wanted to get this and add more wire so I could get down to the 160M range. Your scan show that provably would not have worked well. I suspect a counter poise may be able to change that but probably not. Thanks again de ki7cea 73

[@w2aew]

Yeah, you'd probably need to double up the turns on the transformer, or switch to a different core material such as 75 instead of the 43 type used here.

[@ke4est]

Great how to video! Have a great New Year!!!!

[@TheDrunkenMug]

Nice video, clear instructions and enjoyable ! 👍👏

[@TheCrunchbird]

Great video. Here in NE Florida I use an end fed half wave antenna cut for 80 meters configured as an inverted L. My home made 49:1 UNUN almost identical to the one in the video except I use two toroids glued together. It works from the low end of 80 to the top of the 10 meter band with an SWR low enough for my Icom 7300 to tune with it's internal tuner. Without the tuner the SWR is about 1.6 : 1 on 80 and 40 and about 1.9 : 1 on 20. For those who say that an end fed should be avoided I vehemently disagree. I consistently work Europe on 75 meter phone as well as on 40 SSB and CW with 100 Watts. Early on Christmas eve 2021 I worked E51JD Raratonga, Cook Islands in the South Pacific on the ANZA net on 20 meter SSB. I forgot that I had been testing with low power and was stunned when I looked down to see that I was working Jim with only 10 Watts !!! My UNUN is mounted on a pine tree about three feet from the ground. A 6 foot ground rod is hammered into the ground a few feet from the tree. The antenna runs about 50 feet up the pine tree before it goes horizontal to a second pine tree for a total length of 135 feet. The UNUN provides a direct DC connection to the ground rod which lowers static noise and provides superb lightening protection (essential here in Florida). I do not use any radials or a counterpoise, the coax provides that. By the way, I use a 100pF capacitor across the input, Dave N2SN.

[@NN3RP]

Great video which reinforces the documentation that exist on that website (HF Kits)...I had sent for a bundle of toroids (43) and will be making some of these 49:1 UNUN....Dave, what is the purpose of using two toroids? More power better performance? Both? Rafael / NN3RP

[@TheCrunchbird]

@@NN3RP Using more than one toroid decreases the losses and also allows you to transmit more power. Steve Ellington N4LQ explains it better than I can. Here is one of his videos: kzbin.info/www/bejne/qaXcaIWijbaigKs

[@NN3RP]

@@TheCrunchbird Thanks, David. I watched Steve's overview of the UNUN. He uses 3 toroids for full power!....This video and Steve's allow ones to fully understand the construction and hardware details; gluing toroids, eyehooks, plastic box, etc.. I am going to try the 3 toroid concept as I like QRO....others I will build for 1 toroid for my travelling purposes. 73s and hny 2022....Rafael / NN3RP

[@johnbauman4005]

Hi David! Studied your reply with interest as I have this kit and planning a similar install in my smallish back yard. Specifically, to what part of the unun did you attach the ground? Did you add a lightning arrestor at some point, and if so, where? Thank you for your help! Kind regards, John - KK7JBZ

[@TheCrunchbird]

@@johnbauman4005 John, I grounded the shield side of the coax to a six foot ground rod. This is a really good way to protect from a lightening strike as the antenna has a DC connection to ground right at the UNUN. It also eliminates static buildup. There is no need for a counterpoise as the antenna uses the coax for that. Some people insist on using one and adding a choke or an inductor to isolate the coax before the UNUN. I and many others have not done that. Both ways work just fine. Be careful not to wind any loops in the coax unless they are near the shack as the antenna uses the coax for its other half (unless you use a counterpoise). I have worked the world with 100 Watts and I have even held a QRP sideband QSO with several Australian stations from my QTH here in NE Florida running five Watts. My antenna is a half wave for 80 meters but for a smaller garden you can use a half wave for 40 meters and still work the harmonics. The antenna can be formed into an inverted V or even an odd shape and it will still provide great results. Good luck, Dave, N2SN in Hilliard Florida.

[@JoseSilveira-newhandleforYT]

Well done Alan! Happy Holidays :-)

[@SeAfasia]

Hi Alan very nice work as usual,next step is on the air,tls for posting ...stay safe 73 Dinos

[@DonDegidio]

Hi Alan, Nicely done build and good suggestion about mounting the capacitor with a switch to take it out of the circuit on the lower bands. Seasons Greetings to you and your family and you all stay safe. 73 WJ3U

[@BigRed1500LC]

Here is a little tip. Move the counterpoise terminal to the same side of the housing as the driven wire. Attach approx 6 to 8 feet of 450 ohm ladder line. Shorten your main line by the same amount and connect it to the main line of the 450 ohm ladder line. The other conductor of the ladder line terminates in mid air. You then have a built in counterpoise for portable or temporary use. BTW I would recommend you install the 100 pf cap in this configuration. This is a combination of the EFHW and Zeppelin antennas. You will usually find that this makes it totally useable on 6M as well.

[@johnbauman4005]

Hi Alan, Thank you for this neat tip. I would like to be able to get the 6m band and want to try this approach. To be sure I understand, one ladder line wire is attached to the antenna terminal and the other is attached to the counterpoise screw. At the other end the driven element is attached to the hot lead and the counterpoise wire is free. Is that correct? In order to put the counterpoise screw on same side as fed wire, the enameled copper wire has to be brought over the transformer. Can't that short the transformer coil? Should it be covered with tape to prevent that? For my 2nd floor setup I propose a short coax feed line be attached to a coax connector on my MFJ window pass-through panel which is ~10ft up. On the outside, the 49:1 unun will be fed by a 1-2ft piece of coax and hang on the side of the house from the mounting screw on the unun. The driven wire will be strung across the back yard to a couple 20ft fiberglass poles. The driven wire will also befitted with a homemade coil to access 80m as per kit directions. Since this a semi-permanent installation at my QTH, how would you recommend grounding it? Thank you for your insights! 73, John - KK7JBZ

[@W1RMD]

Looks like fun. I'd like to see an on air performance test in a future video. Thanks and 73's!

[@IZ0MTW]

I bought already two kits from them, impressed with quality vs price. Also they sell a nice quality wire for making wire antennas, with teflon inside, very good for long wire antenna. Thumbs up for them. Thanks for this useful video tutorial. 73

[@BlackHamRadioUniversity]

I made my own and purchased the materials from Home Depot , Lowes and the Toroid from Polomar. It cam out well and only cost me $45.00. Exact same parts/build 49:1 UnUn for endfed antenna.

[@hubercats]

Hi Alan - I just assembled this same kit from HF Kits. After completing the assembly I took another look at the orientation of the SO239 connector. I’m relieved to see that I installed the connector the same way you did with the square plate on the exterior of the box, which is opposite of what’s shown in the instructions. Having the plate on the interior seems to invite water penetration. I’m now building a choke kit from HF Kits and find the same issue. I’m going to go with my intuition and install the plates on the exterior. - Cheers - Jim (KK7CSC)

[@PercivalFakeman]

I built mine with two toroids with good results. Used it with a half wave at 40 Meters. Tunes all the hf bands including 6 meters, except for 10Mhz. Seems to be a good compromise for power handling, efficiency while still being matchable on the higher frequency hf bands.

[@jil2net]

Thank you! It's also would be great to see a real antenna testing with this balun!)

[@jawaidmughalmhsh7012]

Really very great work, God bless you. 73's and Best Regards. Jawaid. (Member of PARS)

[@DK5ONV]

Beautifully built.... 💯🎸🙋‍♂

[@joopterwijn]

Little bit late 😂 but you probably already had a nice 🎄Christmas….. but still… happy holidays and good year!

[@jsa310]

Great video! Thank you for sharing.

[@theafro]

That's a nice kit (and a decent job of building it!). I know what it took to build my own (smaller) one from scratch and that's a very neat solution. Although end-fed antennas are to be avoided if possible, they are fantastic for portable work, or for situations where options are limited. there's nothing quite like throwing a wire up a tree and working the world! so I'm a firm believer that all hams should have one of these and a couple of bits of wire in their shack for when the dipole/beam/magloop gets blown down in a gale and they want/need to get on the air! Thanks Alan! nice to see you back again!

[@alexdokic5567]

Working the world on an end - fed wire is magic, and must be tried as it is easy to make, not too bad on the eye, and has a low cost!!

[@theafro]

@John Cliff You can use a perfect antenna, if you happen to live in a perfect spot in a perfect world. yes, end-fed antennas are a terrible choice when you've got the option to use something else. but personally I quite like a very simple "chuck-it-up-a-tree" halfwave for when out roaming and i've got a half-hour spare to play radios. theoretically not the greatest, but for QRP mobile, it works just fine (uk-aus on 5w while having a picnic is good enough for me!)

[@robertcullipher3492]

Experience needs one piece of advice. When operating, it is best to have a common mode choke on the feed line at approximately .05 wavelengths from UnUn for the lowest band you use (80 or 40). This is best regardless of attached counterpoise.

[@w2aew]

Great piece of advice!

[@wd8dsb]

Yes, just use common mode choke 0.05 wavelengths down from the feed point on the lowest band and don’t use an external counterpoise (AA5TB was the first to propose a 0.05 length counterpoise as being adequate based on modeling, and I have also confirmed 0.05 wavelength is adequate based on modeling). The outside of the shield for the first 0.05 wavelengths of the coax is adequate counterpoise. Having the choke also does a great job keeping RF out of the shack. I use a 40 meter EFHW mounted horizontally using the 0.05 wavelength choke concept and could not be happier. My choke is 14 turns of RG58 on an FT240-31 toroid core and this choke is based on the work done by K9YC.

[@salebowsadventures293]

@@wd8dsb So your RG 58 is wound around a toroid? like the whole coax? or would RF chokes like snap on work also?

[@jeansalomon371]

super explication !! merci ..😉

[@EddieVfgi]

I have built many of these using different mixes, your job is Very nice, looks good. Many that you see are sloppy around the core, again, Nice

[@fullwaverecked]

Great video! Cheers!

[@fullwaverecked]

I need to Google 40 Meter, 20 Meeters, and 2 Waves... Again. Do us a short video on this Crazy Meter Stuff (CMS). It would be greatly appreciated. I finally did myself a big favor and stopped cold trying to figure out what impedance is. Ambiguity Tolerance works like a champ. Thank you for all you do for us out here in bazzaro world... Ehrrr, I ment You Tube World. Cheers from Uta!

[@SuburbanDon]

Nice. I have a similar setup I have yet to start with. I'd be interested to see how you set up the antenna and performance.

[@montygore]

Hi Alan. Good video. I found something that works great on my baluns. I ordered some silicome tubing with inside diameter the aize of the wire. Its high heat and hels keep the wire from shorting to torid. 73 W5DN

[@graybeardradio7778]

Alan, great content as always. You could put a S0-239 "T" between the coax and the input so you can add the 100pF when you need it for the upper bands. Also, I saw you get spotted on 40M CW last night, were you out testing the 49:1? Happy Holidays, 73 de KB7ZUT

[@w2aew]

No, I wasn't. I may try to test it out later this week though.

[@clems6989]

Alan I wish you do a video measuring the losses associated with these Transformers

[@trackerdan1]

Great build video -- quality content as usual. Couple of questions (since I've usually dealt with dipoles): The instructions don't mention much about the counterpoise. What sort of counterpoise would one start off with for this antenna (what is the counterpoise actually needed for)? Would the coax cable act as a counterpoise, and might there be stray high voltages in the shack as a result? Should I ground the coax at the entry point into the shack? Would this antenna produce a pattern similar to a dipole at the base resonant frequency? I think this would be a fun antenna to experiment with! Thank you and 73.

[@w2aew]

In general, the coax shield will form the counterpoise. Unlike a dipole where the feedpoint impedance is low, and thus a low-impedance counterpoise is needed, an EFHW feedpoint impedance is high, so the counterpoise can be high impedance also. Another commenter offered great advice - add a common mode choke to the feedline at about 0.05 wavelengths from the UNUN at the lowest frequency of operation. That'll generally be all the counterpoise you need with an EFHW.

[@johnbauman4005]

@@w2aew Hi, I plan to have only 2 feet or so of feedline outside the radio room/window pass-through with the unun attached to the side of the house and wire running out to a 37ft pole in the yard. There really isn't much feedline to "choke" or to act as a counterpoise. As a consequence I plan to create an 8ft ladder line counterpoise as suggested by one of the other commenters. In this set up would you still anticipate the need for a choke? I don't have 0.5 wavelength available. Thanks! Kind regards, John - KK7JBZ

[@iw0hex]

Very nice, well done ! Happy 2022. 73s Pasquale IW0HEX

[@jaywardjulian6163]

Great video, have a safe holidays and Happy New Year 2022 73 de KH2ZZ

[@paulhastings3109]

Been thinking about this from ARRL 73 KQ4CD

[@AL6S00740]

Lovely, i would like to know how can you test / check a choke if it dies what you expect it to be doing with a nanovna?

[@MacksCurley]

The inductance & capacitance of the antenna, the length of the counter poise and the length of the coaxial cable will determine the final swr reading. It would be great to see details of the final setup of the antenna. 73 M0JZR

[@w2aew]

Ideally, if it is cut as a half-wave length of wire and properly mounted, it *should* have an endfed impedance that is 2500-3000 ohms resistive. Of course, there are a lot of variables that can alter this...

[@MacksCurley]

@@w2aew Yip, that is why it would be great to see the final setup. Thanks for all the great videos and the reply Alan.

[@ralph9987]

Brilliant video as always. I have seen this version with the twisted double wire and then the version that is just tapped. Which version do you think is better?

[@geirha75]

Thanks for very nice instruction on building the end fed halfwave UNUN transformer. Any information on the capacitor? Did it improve the SWR?

[@jimedahl]

Can you do a video of how to measure the loss of the transformer? Maybe also stack two 43 and three 52 mix 2.4” cores?

[@HeimirThorSverrisson]

I've seen considerable loss in smaller versions of this design. A decent SWR against a set of resistors only tells a part of the story.

[@tav9755]

Thanks Alan, for another great video that helps me on planning for my first rig, if I pass the license exam. I will order one kit myself and see, what it can do for my situation. I am mainly interested in HF Bands and DX Connections. The trouble is: I live in an apartment and the only way to set up an antenna is on the attic and I will run a coax between my flat and the attic through an unused chimney. Would you expect sheath current along the coax? I will probably need a Antenna tuner? (I am planning for a Yaesu FT 891) - P.S. You are a great inspiration and your videos motivated me a lot in trying to make the european CEPT novice license. Keep on the excellent work. Hope to meet you on the bands some day

[@w2aew]

The coax shield becomes part of the counterpoise of the end-fed halfwave antenna, which is why you will want to include a common-mode choke on the coax. Practical advice says that placing this choke at 0.05 wavelengths down the coax is acceptable. The EFHW is typically a single-band antenna. Results when mounted in an attic will be a compromise. For multi-band use, you may have better luck with a twinlead fed dipole and a wide-range balanced-line tuner.

[@tav9755]

@@w2aew thanks for the quick reply. Will dig deeper into the twinlead fed dipole!

[@donaldshields2483]

You did a very good job building it how long of a wire did you use on the antenna how many feet thank you God bless

[@w2aew]

I used approximately 68' for a 40m EFHW, and trimmed to resonance

[@hubercats]

Hi Alan - Thanks for another helpful video. The device you built seems to provide impedance matching, at least. Does it also choke common mode current traveling down the outside of the feed line coax shield or would a separate choke on the outside of the feed line and proximal to the antenna feed point make sense? - Thanks! - Jim (KK7CSC)

[@w2aew]

It does not provide any common mode rejection. It's a good idea to add a common mode choke to the feedline, generally at about 0.05 wavelengths from the UNUN - that'll give a sufficient counterpoise.

[@BaldurNorddahl]

you can buy a kit for a common mode choke at the same place. It will look almost the same 🙂

[@elwood.downey]

Good stuff, thanks. Can you sweep again with the cap connected temporarily? I'd just like to see its effect.

[@w2aew]

Here it is - stays below 1.5:1 with a 3K resistive load for all bands betweeen 75m and 10m: www.qsl.net/w2aew/withcap.JPG

[@elwood.downey]

@@w2aew Looks good, thanks.

[@YoramRotbach]

Great video as always! Could you please explain the SWR curve from 80 to 10m? how I was expecting a flatter curve. Is that dependent on the specific core material or the way you've built the load?

[@w2aew]

The rise in SWR at low frequencies is likely a combination of the core material and number of turns resulting in inadequate inductance in the windings. The rise at the higher end is likely due to core material properties.

[@eoinm0nvk110]

Could you explain the theory behind the Capacitor?

[@PapasDino]

Nice work as usual Alan, thanks for sharing. Merry Xmas and HNY! 73 - Dino KLØS

[@dolandump]

Great video. I do have a little trouble understanding the theory behind crossing the core with the secondary winding. It's not the first time I've seen this, I can imagine there are reasons for it. I understand that it tends to decrease the parasitic capacitance of the winding. But I have trouble with the fact that it is wound in the opposite direction of the first section: the core is the same: is it correct "magnetically"? The flux goes in a certain direction in the toroidal core, if the second section of the secondary is wound in the opposite direction of the first one, doesn't this cancel (or decrease) the induced current in the secondary? Excuse my vague comments but I don't have the theory to understand these components.

[@w2aew]

If you look carefully, the direction of the windings isn't changing - the entire thing is wound with the wire coming up through the core and over the top, around the outside and repeat - even after the skip over to the other side of the core.

[@dolandump]

@@w2aew Indeed, I invent problems where there are none (it is inherent to my personality). You have just answered a question that I have encountered many times. Thank you very much for your help!

[@petarpetrov6388]

As far as I know, it is done this way to get the "exit point" of the transformer at the opposit site of the "entry point".

[@R2AUK]

Nice build, Alan. Personally, I've never had success with _multiband_ EFHWs with a transformer on a ferrite core, and I tried like 5 times with slightly different transformers (1:49 / 1:64, different core material, autotransformers / galvanically isolated). It seems that all the online reports on successful builds of such antennas don't use a 1:1 balun and use the feedline as a part of the antenna. Also, I measured the losses in the 49:1 transformer on an FT240-43 core and got about 1 dB or 20% of power which is huge (a 1:4 transformer in a City Windom has only 4% of losses). This being said, Fuchs antenna, City WIndoms and single-band EFHWs work just fine. I wonder what your experience is going to be like. 73s from Russia!

[@w2aew]

I was planning just using this as single band, changing the wire when I want to change bands. This will mainly be a portable/temporary antenna for when I operate in the field. I do have a Par Electronics tri-band endfed (which has a loading coil in the antenna wire), and it works great.

[@R2AUK]

​@@w2aew Well... for a single band you don't really need a 1:49 transformer. You can build a "vertical dipole", i.e. build half of the dipole from a wire and another half from a coax, put a 1:1 balun on the end of the coax. In other words, similarly to City Windom, but without a 1:4 transformed and with the feed point in the center. The effect will be the same, except no power will be wasted on heating the core 🤷‍♂️ Speaking of Par Electronics tri-band endfed, does it has a balun, or it uses the feedline as a part of the antenna? Did you measure the radiated power compared to other antennas in the same conditions? Multiband EFHWs work for sure, I've built one that "worked" myself. The problem is that efficiency is very low compared to pretty much any other antenna.

[@w2aew]

@@R2AUK For portable operating, I usually don't have enough room for a length of coax that is equal to the antenna length, so a City Windom config wouldn't be convenient for me. The Par unit has a matching box which I would imagine is a similar 49:1 transformer. I haven't opened it up since it is sealed. Most of my operating with this antenna is at QRP levels, and I have really good luck with it, so I don't agree that the efficiency is very low. I think it is nearly as good as a dipole.

[@R2AUK]

​@@w2aew Fair enough. From the practical point of view, it is indeed almost as good as a dipole. Luckily it's impossible to notice 1 dB , or even 3 dB difference OTA. And it will not matter if conditions are OK and your goal is to make a CW contact with a random OP (making SSB contacts when conditions are poor is another story...). I'm not trying to prove that you are using a wrong antenna or anything like that :D In this case, I'm interested in antenna theory, particularly if it's possible to make a "fair", say, 10/15/20/40m EFHW with sharp dips on the SWR plot (otherwise it indicates that it has more in common with a dummy load than with an antenna). To my knowledge, it doesn't work, despite what some online reports may tell. The reason is that on 2nd harmonic the commonly used 0.05 λ counterpose is not 0.05 λ anymore, and the end effect works only once. Electrically, the feed point gets moved closer to the center where the input impedance is far from 2450 Ohm and closer to ~500 Ohm. At least that's what my measurements told me. But in case you are interested in this area as well, I would appreciate a second opinion.

[@adrian_sp6def]

I often see that primary and secondary coil are twisted together. Why we do that? Will unun does not work without that twist?

[@mortimersnerd801]

...here's another tip... Assuming the core materials is a quality #43, such as sold by Amidon, build that thing with a larger diameter wire....#16 and reduce your I/R losses at the low Z point... particularly if you run more than 50 or 100 watts. My similar 49:1 with a 110pf capacitor on a 130' EFHW sloper gives me 1:1 on 7, 14, 21, and 24 mhz... 1.5:1 on the lower end of 80 but acceptable higher up, and 1.7:1 at 28.4. You have to do your measurements in an in situ environment. It's almost like a black art... My counterpoise is the coax shield on some LMR 400.. nothing else, no common current chokes and no funny coax lengths...This is pretty much the same as the way MYAntennas do things.. and yes they have it figured, so y don't have to reinvent the wheel here. VA7AA

[@fullwaverecked]

Alan. Since we are all so busy with life that we could puke... Let's all start a major project for bringing all the electronic "GOATS" onto one live stream. You, Paul, Dave, and Ringo... You know what I'm saying. Uncle Doug, etc. Five across and two deep. Like Hollywood squares. Let me know what you think, and I'll keep pulling from my end. Cheers! FW.

[@w2aew]

I'd be up for that.

[@fullwaverecked]

@@w2aewBut that would be cool. Ten of the top, one hour once a week live stream. Are you feelin it? And we could rotate five to keep it alive in the hive 🤟

[@needlethread4715]

can i use a smaller toroid for this build? exact same size and turns of magnetic wire but a smaller toroid?

[@Mojomo777]

May I ask a questions, how do we measure the efficiency of the UNUN, what can be done to improve the efficiently from the winding or better core material? I am running QRP and the ability to get as much as tx power to the antenna will be the ideal goal with limitation of power. Thank you in advance.

[@dalependleton6420]

Mount the stud for the counterpoise? An end fed antenna DOES NOT require any counterpoise. The stud you are installing is for EARTH grounding the antenna. This helps provide some lightning protection and also bleeds off static charges helping to make the receive with the antenna more quiet. ARRL folks you need to get your terms correct!!!

[@elconquistador932]

Quick Question, what gauge is the enameled wire in this kit? I've read that these windings are anywhere between 18 and 14 AWG. Thanks.

[@johnbauman4005]

Hi! Re a switch on the capacitor: I found a couple thousand switches when I searched miniature spst on off switch and an assortment of ratings for each of them. Can you suggest a specific switch or switch rating for this purpose. Very new at this. Really appreciate your videos. Subscribed! 73, John -KK7JBZ

[@hankhamner3671]

How do you verify that the impedance range of your actual EFHW antenna is approximately 2,450 ohms resistive (turns ratio squared x 50 ohms)? Is the reason your test SWR is not 1:1 is because of the reactance of the resistors combined with the non-linear reactance (mainly inductance reactance) of the transformer? Also, I am puzzled about the purpose of the primary capacitor and how the toriod mix ( 31, 43, 52, etc.) affects the impedance match and how to increase power handling capability of the transformer. I would appreciate you elaborating on these questions. I have learned a lot from your many fine videos.

[@rickeaston3228]

I would have liked to see the same test done but with a choke wound toroid or just a core at the input at the coax connector. The purpose would be to see if the coax shield has RF on a part of it. Sliding a toroid core down the coax toward the radio might show how much of the shield is working as the rest of the antenna. Is .05 wave length of the shield used?? If not, how much.

[@w2aew]

I'll include that as part of the antenna test when I do it.

[@ajderking]

Hi guys, Don't seem to get it to sing properly. Is the second ratio now six to eight or seven to seven. Twirled or straight first winding. Please advice.

[@paulkazjack]

Can only enamelled wire be used?

[@californiakayaker]

This is an excellent kit. I noticed at the web site (hf kits) mine started with the german language, was surprised. I clicked on the British flag and it went to english. One guy did a test for temp increases and he used his fingers to measure it. Not exactly smart. I'll try it with a high powered 3000 ohm resistor possibly, and a thermal infra red reading point and shoot thermometer. So many of these kits come out with small toroids, not good. I really like this one but I'll be building with my own toroid ect.

[@AlvinMcManus]

QUESTION?? Do I need a counterpoise if my feedline coax is over 25ft?? It will be closer to 55-60ft.

[@w2aew]

Generally with an EFHW, no.

[@hubercats]

Hi Alan - One more question follows: I have a coax crimping tool appropriate for SMA connectors, and I have LMR 240 and RG-58 coax. Would it be okay to replace the SO-239 connector with an SMA one or is such ill-advised? -Thanks again - Jim (KK7CSC)

[@w2aew]

You can switch to SMA - it is a better RF connector at higher frequencies, but not as physically robust (more easily damaged).

[@picwiz2]

Dear, is it really necessary a very high voltage capacitor if it is connected to the transformer primary? If everything is ok and the load seen by the tx is about 50 ohm, the voltage should be around 70 volts. I agree of course if it is on the secondary side but in many project there are high voltage capacitor on the primary. Why?

[@jorgerodriguez-wp6en]

Hello there sir. Excellent your video of Un-Un 49:1 A question. I have very small Amidon 50-43 toroids. They are really small. I want them only for a Un-Un receiving antenna (SWL). Do I have to put the capacitor 100pf too? .. Thanks for reply. 73 George

[@w2aew]

Probably not, it would likely make very little difference.

[@AboubakrA]

Hi Alan, thanks for the video, I had a question though, sorry if it's a stupid one, but why do we need the double wires for the first two turns and then single wires for the rest ?

[@w2aew]

The transformer has two windings - a 2-turn primary and a 14-turn secondary. This gives a winding ratio of 7:1 which results in the impedance ratio of 49:1.

[@AboubakrA]

@@w2aew ah ok so you double the wires for the primary to match the wire resistances somewhat, right ?

[@w2aew]

@@AboubakrA No. The double wire is just a convenient wrapping technique for the primary.

[@AboubakrA]

@@w2aew got it, thank you so much

[@stephaniestephanie1290]

It's a clearer video with clearer pics than arrl website direction. The different solder configuration from the ARRL directions confuses me. As primary here is pigtailed. But the other directions don't do a pigtail.

[@w2aew]

I mistakenly didn't leave enough wire, that's why I did the pigtail.

[@twong689]

It looks like your turns are spaced apart on the toroid. I have seen all the other products with tight spacing, especially keep the input windings away from the output is preferable.

[@w2aew]

Tight windings increase the interwinding capacitance, which I want to avoid.

[@twong689]

@@w2aew What about coupling from the primary to the secondary?

[@alvarogaitan2529]

fantastic video thanks 73 from kb2uew

[@ernestb.2377]

Did you needed counterpoise with this EFHW dipole? I am currently working on the similar kit but 100W, and will try to realize ca. 12m wire with coil, to do 10, 20 & 40m band.

[@w2aew]

Generally the coax shield will serve as the counterpoise. Some people find it helpful to put a toroidal choke part-way down the coax, but I haven't found it necessary in my case.

[@NGinuity]

Do you have a video explaining the math behind 49:1 and how you get that from a 2T:14T here? I also see others with 3T:24T in a Mix 43 configuration. That is eluding me and I can't presently find anything that explains it.

[@w2aew]

Both 2T:14T and 3T:24T are a 7 to 1 turns ratio. 24/3=14/2=7. The impedance ratio is the square of the turns ratio. 7*7=49

[@NGinuity]

@@w2aew Easy enough. Thank you! Is there any advantage of using more turns or less turns to get a ratio?

[@w2aew]

@@NGinuity More turns are generally used at lower frequencies to get the inductive reactance of the windings higher.

[@usernamemykel]

Would you be able to tell me what gauge wire was being used, and, if 28 gauge would work as well? Thank you! 73

[@w2aew]

I believe it as 16 gauge. 28 would work, but would have more ohmic loss.

[@usernamemykel]

@@w2aew Thank you

[@BlackHamRadioUniversity]

How long was your antenna wire? 66ft?

[@w2aew]

I don't recall precisely, but it was between 65' 6" and 66'.

[@joeb3300]

I built the same kit (sold by ARRL, for Field Day 2021) and have been very happy with it. It is currently my only HF antenna. I do believe that the "250 watt" rating is more marketing-inspired than real: running digital, with 50W, I saw some SWR changes (rises) during long transmissions. The toroid was probably getting hot. It was fine at 20 watts, where I normally operate when doing FT8. Even when using SSB/phone, I suspect 250 watts will risk damage to the transformer. Given how easy it was to construct, I bought some FairRite (brand) cores on-line and hardware from Home Depot - I'll try to build a version of the transformer with two cores in parallel.

[@youtubeaccount931]

What would be the characteristics on 7mhz with the capacitor installed?

[@w2aew]

Very similar. The capacitor really only affects the higher HF bands.

[@youtubeaccount931]

@@w2aew oh ok thanks! I'm building one for mostly 28mhz use

[@RobB_VK6ES]

May I make a request Allan. I have made a few baluns in the past but the subject of baluns, ununs and cmc's is a real minefield of good advise, anecdotal evidence and flat out misinformation. May I ask you do a video or 2 covering core size/mix and wire sizing for various frequencies and power levels. When is it a transformer when is it a cm choke. wire wound and coax wound variations. I have on the bench at the moment a 2 core ft240-43 1:1 balun that I am making for a 80/40/20 dipole. Is this likely enough to handle 1kW pep ?

[@SolarDrew]

What gauge wire is that on the toroid?

[@w2aew]

18 gauge, 1mm wire

[@okhamradio]

I built it, but it doesn’t work properly. I think cause is a wrong toroid 2000MH

[@MountainRaven1960]

What is the core material made from? Is it a FT240-43?

[@w2aew]

Yes, that is what is supplied in the kit.

[@scollyer.tuition]

What is the purpose of this device? Is it purely for impedance matching between the antenna and txer, or is there more to it than that? If so, is it not just a transformer? (I apologise in advance if I'm being clueless - I know next to nothing about RF electronics)

[@w2aew]

It is an impedance matching transformer for the special case of 1/2 wavelength long end-fed antennas. These types of antennas have a resistive input impedance that is 2500-3000 ohms or so. It therefore transforms the antenna feedpoint impedance down to 50 ohms to provide a good match for transmitter/coax feed.

[@scollyer.tuition]

@@w2aew Having tried to educate myself about baluns/ununs, if I understand correctly, they play two roles. 1) They perform antenna-txer impedance matching 2) They convert, if necessary, from an unbalanced txer to a balanced antenna. (or vice versa) However, there seems to be limited good quality technical info avaialble on the web (I can find plenty of confusing explanations, and old-timer's rules of thumb) with not much stuff that starts from a decent basis in physics or electronics. Is there any chance that you could do some videos on this topic, covering say antenna impedance and what it depends on, balanced and unbalanced antenna feeds, and how baluns/ununs are designed and principles of operation (there seem to be quite a few variants - voltage/current baluns etc). I'd be very interested to see this.

[@Aleziss]

4:07 uh, I would have thought the ground side on the primary would have been the single wire but you did the opposite... in my head, it's like you are shorting the end of the secondary winding to ground ?! but that is me not clearly understand how this is working because you sure do know what you are talking about ! And if you ever reply, can PTFE wire could be used instead of enameled wire ?

[@fullwaverecked]

Ok then. I gotta go talk to the five feral cats out back over dinner and see what they think... It kinda went from cool cats to smart cats... Cheers!

[@richarde735]

@01:10 nice marking gauge… where’s norm?

[@w2aew]

Got is autograph on a book or two in my woodworking library...

[@richarde735]

@@w2aew he’s gotta be getting old by now.

[@w2aew]

@@richarde735 Early 70s.

[@frequencywatchers]

Youi Shoulda Put The 100Pf Capacitor On A Switch And Test It With It On And Then off, Then We Would See Whats The Diference On SWR Metyer :)

[@krish-vu3ocg-565]

gauge of copper wire?

[@w2aew]

16

[@ltlt6117]

Hi What is the difference of balun or unun?

[@w2aew]

BALUN = Balanced to Unbalanced transformer UNUN = Unbalanced to Unbalanced transformer Balanced means that the two conductors have an equal but opposite voltage swing on them - like ladder line or the center feed of a dipole. Unbalanced means that one of the two conductors has little/no voltage change, and all of the voltage changes are on the other conductor - such as in coaxial cable.

[@ltlt6117]

@@w2aew baluns or ununs just will use in impedance matching? So what is 1:1 balun? It has a same ratio!

[@w2aew]

@@ltlt6117 A 1:1 BALUN is typically used to interface coax (unbalanced) to a balanced feed antenna such as a dipole or loop.

[@ltlt6117]

@@w2aew thank u so much for the complete answers.👍👍👍

[@Nobody-ld7mk]

While the EFHW transmits... I personally find it to be the best all band HF SWL antenna I've ever used in my 30 plus years of amateur radio. My build is 10 thru 40 meters transmit @ 68 feet of conductor (bare) and below 7 MHz the resistance at the rig drops to 10 ohms on the 75/80 meter band. Transformer offers improved signal to noise with minimal insertion losses. My arrangment uses a 30 foot aluminum mast as a counter-poise with a 1-M ohm 1 watt resistor across a home brew blitz bug to ground. AEW's "perfect score production" videos are a valuble contribution to the amateur radio community, sure take some of the head banging out of learning. Common Mode without doubt is an issue if you plan to transmit. Enjoyed the demo. "Cool Stuff" N0PLV~ Tnx... ( I did end up adding a 100 pf HV cap to complete the Pi-L primary side of the transformer on mine.)

[@w2aew]

I'll see how much common-mode is a problem with this antenna. I also use a Par Electronics EFHW for portable operating, and never had a common-mode problem with it.

[@tcarney57]

I've made a few of these 49-to-1 ununs from scratch, but it looks like the kit is nice because you don't have to round up all the parts yourself. I used 3kV caps in mine, suspecting there's going to be some high voltages. It's never been clear to me how the parallel capacitance effects the lower bands. I use these mostly for 40M, and you've left out the capacitor for use on the lower bands. What effect is there on those bands with the capacitor in-circuit? --73, Todd K7TFC

[@w2aew]

I temporarily added the cap and re-swept it: www.qsl.net/w2aew/withcap.JPG

[@tcarney57]

@@w2aew It looks like it brought the apparent SWR down from a low of 1.2 before to 1.02 with the cap added. It also looks like with the sharp dip at to the new low bottoming out at ~8300KHz that it might be close to 1.2 anyway at 40M. Of course that's with a purely-resistive "antenna," but it looks pretty good. Thanks for experimenting with that! --73, Todd K7TFC

[@tamaseduard5145]

👍🙏🙏🙏👍

[@rasputinputin8103]

It is a transformer. Not an UNUN. Three cores will allow you to use 1.5KW. 16 AWG is better than 18AWG. The capacitor should be100pF at 6KV (blue) rated, not 1KV (light brown), as is shown. If you use more than 200W, this core will saturate and will get very hot. Using two, or even, three cores will stop the core from saturating. The long wire has 2500:Ohms, so a 49:1 transformation will bring this to close to 50:Ohm. The wire should be cut 3.550:MHz. This will be 45.253m = 148.ft & 5.6 inch. This will now be resonant on all bands, except the WARC bands, where you will have to use the ATU. To work 160m band, remove the transformer and use the wire as a 1/4 on 160m (1942:MHz). You can switch in another 6m to go lower in the 160m band. Be very careful to use the counterpoise wisely, as it can be seen as a half-wave dipole with an offset fed. The coax should have at least 12 clip-on ferrites before the cable comes down to the radio shack. I use a Palstar-HF Auto that connect directly to the transformer. This is controlled remotely via the Palstar HF Auto-R (remote), via a 100ft a serial cable. There should also be another 12 clip-on ferrites at the radio end, and yet another 12 clip-on ferrites at the 16ft 6 inch from the 23ft ugly choke wound on a 5" diam plastic waste pipe, that connects directly to the Palstar or other ATU. Good to go.

[@1215Runnymede]

It’s an UNUN because you are matching an unbalanced coax to an unbalanced wire antenna. 73 de K6ROQ

[@w2aew]

Good info, thanks. I won't be using anything more than 100W, and mostly less than 10W, so the supplied 1kV cap will be fine. No room here for a 148' wire, so mine will be mainly used for 40 and 20m. I'll experiment with CMCs when I start playing with the antenna.

[@sammin5764]

🌟🌟🌹🌟🌟

[@ve3sif]

thanks for the video. I've using the HF Kits mini end fed in the field. And I just built a homebrew version for QRP: kzbin.info/www/bejne/hpa5e6F_mJ6qbrs workable SWR on 40, 20 and 15. 10 meters, not so much :( 73 Ron

[@hobbygaertner420]

Good kit except for one part: STOP THE SO239/PL59 Connectors! Just stop using them. Just use BNC or N Connectors. Seriously. in 2021, if you want to offer a PL or SO connector, just provide a cheap adapter to BNC or N

[@BaldurNorddahl]

That is exactly what I am doing. I got the same kit but I put the SO239 in the bin and installed an N-connector instead. Not that it matters at most HF band but I have standardized on one connector in my shack. I want freedom to use any of my cables on both HF and VHF/UHF.

[@WestCoastMole]

N Connectors do present lower loss at the upper end of spectrum (above 200MHz) but SO-239s work just fine at HF Frequencies and have an advantage over N Connectors in that they have a higher, yes HIGHER, voltage breakdown potential.

[@digitalradiohacker]

I own, and my job means I work with, a lot of UHF gear. Also, my gear is in constant flux, so nothing stays in place for long, with items being swapped about pretty regularly. As a result, all of my coax, antennas and other acessories have either been fitted with, or bought with N-type connectors. Wherever a radio or peice of test gear has some other connector, I use an adaptor. This has served me much better than trying to remember to bring or use a specific cable with certain connectors for a certain job. It's more of a convenience thing for me.

[@EUC_Senior]

That's a really expensive unun kit! You got a few dollars worth on parts and you need to all of the labor and this kit costs how much? I'm not the smartest person in the world but I think I will pass on this one!