Tuning an End Fed Half Wave for POTA

[@theoldhobbit3640]

Just found your channel, in particular the 49:1. These are the only EFHW antennas I use QRP/P as I do not need a tuner on the main 4 bands I would play on, my FT817ND copes very well with this antenna. I build my own lightweight 49:1's and often give them away to others who want them, otherwise they would just lay around and gather dust. Thank you for sharing.

[@aa3konthego]

I also have a KM4ACK EFHW for my QRP work. I've really come to enjoy this antenna for its get setup and go abilities. As long as the torroid is appropriate for the power level the only difference from one to the next is the physical size and amenities of the design like a built-in line winder.

[@craiger953]

Thanks for the video and for showing the coupler. Yesterday, I contacted the seller on ebay and ordered one. He shipped it within an hour of receiving the order and tracking indicates that I should have it tomorrow.

[@aa3konthego]

You're welcome! Yes, Walt from TennTennas is very responsive. I had a question about case plastic and he responded in less than a day.

[@craiger953]

@@aa3konthego Yes, I had several emails exchanged with Walt. He’s been licensed even longer than my 55 years. Question: What do you think about using a Harbor Freight 20’ push-up flagpole? Is it high enough for an EFHW? If I attached the antenna to the pole with a foot of rope, would the aluminum affect the tuning very much? Thanks.

[@aa3konthego]

@@craiger953 Hmmmmmmm... That is something I have not considered. Most of my portable installations of this antenna have been 20-30 feet up with stellar performance. However, the end point of the wire had always been in a tree. I have a rope and pully on my tower and an idea for a new video. At the least I'll have an answer for you by this evening.

[@craiger953]

@@aa3konthego The push up flag poles are cheap - $60 for the pole only and $91 including a drive-on mount. That’s a LOT CHEAPER than the carbon fiber push-ups. I didn’t mean for you to do more work, but maybe that’s another video for you. Thanks.

[@aa3konthego]

@@craiger953 Playing with radios and such is not work but passion. Ran some tests and the fast answer is; GO FOR IT. 40 to 10 stayed resonant with the far end of the wire and the matching box at the top of the tower. I'll have a video out showing what I did but won't be able to start editing before next weekend due to an obligation this week.

[@billlazzaro1401]

I just put up the antenna. My first contact was on 10 m: Victor Echo 6 Charlie Quebec in Calgary! Nice! Thank you. N2CF Cook on, Chef!

[@aa3konthego]

Great job!

[@billlazzaro1401]

I found your KZbin channel after the NDOG. I appreciate your insights on this antenna and tuning. Thanks for the golf cart ride. Bill, N2CF

[@billlazzaro1401]

BTW, I met Chet KE4VXC at the Round Barn today. We talked ham radio and Cast Iron.

[@aa3konthego]

My pleasure for the ride. Good to meet you!

[@G0ogs]

The pvc coating on the wire will have an effect on the element length as apposed to bare wire.

[@aa3konthego]

Correct. As I tuned with the insulation on the wire it is factored into the resultant length.

[@davesanders4381]

The feed point is at high voltage and you should have an insulator between your strain relief and the attach point on the mast.

[@aa3konthego]

I'll take a look at that. On a recent POTA expedition the SWR was hitting about 2. But it was the first time I used the large meter on the 7300. The auto tuner took car of the issue. But I want to experiment with the length some more.

[@BargainBasementHamRadio]

EFHW Antennas can be so convenient! Thanks for sharing. Also thanks for making me want to spend my $ to replace my old AA-30 with a new "zoom" model! Love that multiple SWR feature! 73!

[@aa3konthego]

Glad you liked the video. I have plans for a few other antenna videos. Unfortunately my day job gets in the way. Stay tuned.

[@BargainBasementHamRadio]

@@aa3konthego likewise! Be safe.

[@JxH]

11:20 The end of a Half-Wave is high impedance and thus high voltage and thus more sensitive to capacitance, so should (generally) be kept away from metal hardware, especially if the green support post is metal and grounded. It's worth sort-of visualizing the voltage and current nulls and peaks, and keeping track of where there are at various frequencies of interest; it reduces the invisible 'magic' of RF. "If RF was purple (visible), then it'd wouldn't be so mysterious." - me, years ago.

[@aa3konthego]

Agreed, most of the installations have had the feed point tied off to a tree or bush. I do notice some variations in SWR possibly based on how high off the ground it is. That's something I would like to quantify.

[@johnblouch3309]

I love your hat. Where did you get the custom made hat with call sign and name. Thank you for the video. It was fun.

[@aa3konthego]

Thank you for watching and commenting.! I got the hat from an customized apparel vendor at the Dayton Hamvention. You can search the web and Etsy for similar vendors.

[@jrmcdonald963]

Thanks for the step-by-step demo. Are you using a choke on your feed line?

[@aa3konthego]

I normally do But did not when tuning this antenna. One of these days I want to set the antenna up again the same way with my choke and see where the tuning falls. I use an Ultimax choke.

[@ExperienceKevsworld]

I have almost the exact same setup, except I made my 49:1. The swr is at or around 1.5:1 on 40,20,15, and 10m, but for some reason my rec/Tx is terrible. I have a lot of variables here at the house which may be causing interference; nevertheless, I plan on using it for my first pota activation using my IC-718.

[@aa3konthego]

How is your Rx/Tx terrible? Local noise?

[@ExperienceKevsworld]

@@aa3konthego I am convinced it's something here or close to my house.

[@aa3konthego]

@@ExperienceKevsworld Yes getting out to somewhere electrically quiet will help you narrow it down.

[@suttonmatthew]

Great video.

[@jackkb2txr833]

If was me i would remove the antenna wire because it is grounding off the fence with the eye bolt you are tide off at

[@aa3konthego]

I see your point. All of my field I stallions have been to an insulated support and I notice better SWR on 40m. I want to rerun this test using a non-metallic support and will report on that. Maybe use two zip ties to separate the wire from the eye bolt. Thank you for watching.

[@AlvinMcManus]

This is the video I was looking for. (Forget about those droids!) Thanks. I do have a comment; what do you have against heat shrink tubing? It's great for waterproofing and it adds a really finished appearance to DIY wire connections, including coax. Just wondering not judging... 73

[@aa3konthego]

I'm happy that this video is helping you. That is why I produce them! As for heat shrink, I have nothing against it. As this antenna is for temporary use and has never been up for longer than a week while camping, the thought of extra weatherproofing did not enter my mind.

[@davepiggin8997]

A stainless thimble would be a better fixing at the wire/UnUn end to save the wire being chaffed and potential breakage.

[@BikingHikingRadio]

Just found your video Mark. Good job. I have the TennTenna myself and it works well. I believe my EFHW is about the same length. How is the SWR on 30 meters for you (I know you love CW)? Hope we can do a POTA together sometime. 73 Scott.

[@aa3konthego]

I haven't tried it on 30m but will have to. And thank you for subscribing. Some more antenna videos coming.

[@bagginshates]

So you're not cutting the end in the tree, but you put an eyelet on the near end?

[@aa3konthego]

Correct. Because I crimped a stop (double ferrule) at the far end to create a loop for the insulator. At the transformer end I just stripped the insulation off and attached it to the transformer terminal. I shortened the wire there until I had a good match then crimped on a terminal for a better connection. Also crimped the double ferrule at that end.

[@aa3konthego]

I did run the wire through a quick link and a double ferrule at the transformer end and just let friction hold everything in place until I was done tuning. I hang the transformer from the quick link so the link takes all of the stress.

[@aa3konthego]

And just to confirm fuse you more 🤯 I've tuned a couple of QRP EFHW's where I trimmed the tree end of the wire. There I could untie the wire (26 AWG) from the insulator, cut and tie it back on. The end result is the same. If you need x feet of wire for resonance it doesn't matter which end you trim to get x feet.

[@Johnyrocket70]

You can fold the wire back instead of cutting it.

[@aa3konthego]

Having tuned a couple of additional EFHW's that seems to be an easier way. However I had already crimped the loop double ferrule at the end. I also used 14 guage wire and that is heavy. Didn't want the far end to come loose on me when pulling it up.

[@72chargerse72]

Dont cut the wire just fold it back thru the insulator and wrap it around the antenna. you may need it long again some day.

[@aa3konthego]

True though I tend to operate more phone than CW or digital. That being said the external still loads up well on the lower frequencies in each band.

[@denelson83]

You realize how awkward it is to measure antenna lengths in _feet_ for frequency bands given in _metres,_ right?

[@aa3konthego]

Fortunately I have a tape measure that is feet on one side and meters on the other. And If I'm working from frequency as the starting point, the conversion to needed length is one constant or another.

[@denelson83]

@@aa3konthego I just do everything in metres, as it is much easier and I grew up with the metric system. 73 VE7NDE

[@AlvinMcManus]

Ditto on the metric tape measure. I have both a 300ft surveyors fiberglass tape reel and a 30m fiberglass tape reel. Very handy having that metric tape. @@aa3konthego

[@no5x937]

Instead of cutting your wire to trim, try folding the wire back on itself to find the optimal length.

[@aa3konthego]

In hind sight, that and a split bolt and nut to hold things while I got the length established would probably have been easier. I built a KM4ACK EFHW and adjusted it from the far end.

[@yowsa52]

Folding back is not the same as cutting the wire. Cutting the wire changes resonance more dramatically. There is a formula for folding back wire floating about the ether somewhere. Maybe DX Commander had one

[@alexdokic5567]

Hi, thanks for posting this video, I am a big fan of the EFHW Antenna, I have my one in a sort of inverted V configuration, it's amazing how well they work, I don't have a counterpoise attached to the 49-1, as the coax will do the job if its long enough, I think the main tips are getting the centre as high as possible with the apex angle more than 90 degrees if configuration is an inverted V. I'm not sure what the angle of radiation looks like but I managed a contact to South Africa so not too bad for a wire Antenna that is easy to construct and deploy! 73 Alex M0KVA

[@aa3konthego]

Thank you for the comment! I did some quick tests with different lengths of coax on a KM4ACK QRP EFHW I just tuned and did see differences. Using my TennTennas EFHW with over 35 feet of coax, a choke and a little more coax has been impressive. SWR less than 1.5. The only real downside I see to a EFHW is the length. 60+ feet for 40 meters and 120+ feet for 80 meters. Going for an inverted V configuration helps but is still a lot of wire to manage.

[@revbikerbigd8664]

Don't cut just loop it back and tape it !

[@aa3konthego]

I basically did that with the far end of a QRP EFHW I built. But this one I was working at the transformer box so needed to eliminate the extra.