{"id":367,"date":"2026-06-17T18:26:02","date_gmt":"2026-06-17T17:26:02","guid":{"rendered":"https:\/\/ei4hq.ie\/test\/?p=367"},"modified":"2026-06-18T13:25:42","modified_gmt":"2026-06-18T12:25:42","slug":"the-end-fed-half-wave-antenna","status":"publish","type":"post","link":"https:\/\/ei4hq.ie\/test\/2026\/06\/17\/the-end-fed-half-wave-antenna\/","title":{"rendered":"The End Fed Half Wave Antenna"},"content":{"rendered":"\n<p class=\"has-medium-font-size wp-block-paragraph\">My trusty 20M GP antenna, is a much-loved and proven favourite for operations away from the home QTH. Recent experience has made clear however that It&#8217;s not ideal for POTA, SOTA and other short term \/P activations. It&#8217;s relatively heavy at about 2kgs, and it takes about 15 minutes to set up. Of course, it&#8217;s also a single band antenna. That, above all else is a bit limiting.<\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">In my many forays into the world of antennas over the years, I&#8217;d occasionally come across the &#8220;<strong>E<\/strong>nd <strong>F<\/strong>ed <strong>H<\/strong>alf <strong>W<\/strong>ave&#8221; antenna &#8211; <strong>EFHW<\/strong> &#8211; but I didn&#8217;t pay much attention. I finally did take notice when I went looking for a POTA antenna that would perform some way efficiently, while also being light-weight, multi-band and easy to deploy.<\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">When I started looking for an alternative to the 20M GP, I quickly learned that the EFHW is a favourite among POTA and SOTA operators. Despite the wisdom of the herd, I was a bit skeptical of the claims being made for the EFHW. If I&#8217;m honest, it almost sounded too good to be true. Nonetheless, given how easy an EFHW is to make, I reckoned I&#8217;d nothing to lose by putting one together and trying it out.<\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">I&#8217;ll summarise making one first and then talk about my early experiences with using it after. Spoiler, I&#8217;m <em>very<\/em> impressed.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"768\" height=\"1024\" src=\"https:\/\/ei4hq.ie\/test\/wp-content\/uploads\/2026\/06\/C48F6CE1-C40F-44FB-956C-86B4D50BC873_1_105_c.jpeg\" alt=\"\" class=\"wp-image-322\" style=\"width:500px\" srcset=\"https:\/\/ei4hq.ie\/test\/wp-content\/uploads\/2026\/06\/C48F6CE1-C40F-44FB-956C-86B4D50BC873_1_105_c.jpeg 768w, https:\/\/ei4hq.ie\/test\/wp-content\/uploads\/2026\/06\/C48F6CE1-C40F-44FB-956C-86B4D50BC873_1_105_c-225x300.jpeg 225w\" sizes=\"auto, (max-width: 768px) 100vw, 768px\" \/><figcaption class=\"wp-element-caption\">The 5W 40M-10M EFHW antenna gets it&#8217;s first outing at IE-0246<\/figcaption><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">EFHW Basics:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">An EFHW antenna is a half wavelength long on the lowest band of operation. In other words, it&#8217;s a half wave dipole on that band.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Unlike the most common dipole variant however, an EFHW is not fed in the middle but instead it&#8217;s fed at one of the ends.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Feeding a dipole at one end and not in the middle, means a  much higher impedence at the feed point. To match an EFHW to a 50ohm transmitter, a 49:1 un-un is used at the feedpoint.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">An EFHW needs some sort of counterpoise or connection to earth. It doesn&#8217;t need very much at all &#8211; the wisdom is that a counterpoise a mere 0.05 wavelength long on the fundamental frequency, or a short stake into the ground, is sufficient. The antenna does need <em>something<\/em> however. If you don&#8217;t provide a counterpoise, it&#8217;ll make use of whatever it can find electrically e.g. the feedline coax shield. If there really is no counterpoise or earth available, then the antenna won&#8217;t work. It&#8217;s better to have an explicit counterpoise or earth connection as otherwise, you may find the antenna is  inconsistent from a tuning perspective in use, and it could result in &#8220;RF in the shack&#8221; issues at the rig. That&#8217;s not something you want, particularly if you&#8217;re running higher power.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">An EFHW will resonate on even and odd harmonics of it&#8217;s fundamental frequency. As such, it can be used as a multiband antenna.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">If using an EFHW as a multiband antenna, adding some capacitance at the feed point can help with resonance on the higher bands.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Because an EFHW is fed at one end, it&#8217;s an easy antenna to get up in the air, that&#8217;s a big part of its&#8217; attraction. An EFHW can be put up as a horizontal wire, as a vertical wire, as a sloper or as an upside down L. I&#8217;m intentionally not using the term &#8220;inverted L&#8221;, to avoid confusion with that antenna type. The EFHW if put up as an upside down L, looks physically like an inverted L but it works very differently. <\/li>\n<\/ul>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Design Criteria for my  EFHW Antenna:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">Max Transmit Power: 5W.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Bands: 40M, 20M, 15M and 10M.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Insulated radiating wire so it can be run directly over tree limbs, through bushes etc.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Compatible with my existing &#8220;\/T&#8221; and &#8220;\/P&#8221; equipment, so a PL-259 connector at the antenna feedpoint.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Lightweight and compact.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Weather proof.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Low profile &#8211; no bright orange wire or other &#8220;glizty&#8221; parts that might draw attention.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Parts List:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">A length of insulated wire for the antenna wire, that&#8217;s a half wavelength long on the lowest frequency you wish to operate on. I went for 40M, so I used circa 22 metres (67&#8242;) of wire. I used one strand of twin field telephone wire. That stuff is very strong, light and low profile. It&#8217;s also almost impossible to tangle up.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">A second length of wire for the counterpoise. Make that about 0.05 wavelength long on the lowest frequency you wish to operate on. For 40M, that&#8217;s 2 metres (3.3&#8242;). Alternativley, make a ground rod. I went with a ground rod made from a 250mm (10&#8243;) length of aluminium rod I had lying around. <\/li>\n\n\n\n<li class=\"has-medium-font-size\">Type 43 toroid(s). How many and how big they are will depend on how much power you wish to run. As I was only building for 5W, I used FT23-43 toroids. I might have gotten away with even smaller. I used two of them, glued together with superglue. At 5W, one toroid would almost certainly been enough but seeing as how I had two to hand, I decided to take a &#8220;belts &amp; braces&#8221; approach.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">A 100pF capacitor. This is optional but helps the antenna to resonate and in a useful place, on the higher bands i.e. 15M and 10M in the case of my antenna. Again as the antenna is only for QRP use, I was able to use a 50V rated capacitor from the junk box. For higher powers, you&#8217;ll want to use a higher rated capacitor.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">A suitable enclosure for the feedpoint connections. I used a black plastic box with a screw on lid measuring about 80mm (3&#8243;) x 40mm (1.5&#8243;) x 20mm (0.8&#8243;). Sometimes with ferrite based components, you want to avoid using a metal enclosure as it could alter the performance characteristics of that component. I don&#8217;t think this is one of those situations but I&#8217;m open to correction on that&#8230;<\/li>\n\n\n\n<li class=\"has-medium-font-size\">A panel mount SO239 for the coax connection.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">A means to connect the antenna wire and the counterpoise\/ground. I used M5 nuts &amp; bolts and suitable eyes soldered onto the antenna wire and counterpoise\/ground wire.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Making the Antenna:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">Cut the radiating wire a bit longer than calculated, to have a bit extra for tuning purposes. Cut the counterpoise and\/or make up the ground rod.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Drill required holes in the feedpoint box.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Mount the coax connector.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Wind the 49:1 un-un. This is the only bit that requires some care. Rather than repeat excellent guidance that&#8217;s already on the internet by other kind souls, take a look at e.g. <a href=\"https:\/\/mm0zif.radio\/current\/2024\/11\/the-marvelous-491-unun-what-it-is-and-how-to-build-one\/\" target=\"_blank\" rel=\"noreferrer noopener\">MM0ZIF&#8217;s instructions<\/a>, <a href=\"https:\/\/www.qsl.net\/nf4rc\/2020\/ResonantEndFedUnUnConstructionManual.pdf\" target=\"_blank\" rel=\"noreferrer noopener\">Gordon Gibby&#8217;s instructions<\/a> or <a href=\"https:\/\/km1ndy.com\/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna\/\" target=\"_blank\" rel=\"noreferrer noopener\">KM1NDY&#8217;s instructions<\/a> (thanks folks!).<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Connect the antenna wire to the secondary wire of the un-un, one end of the primary wire pair to the counterpoist\/ground and the remaining primary wire to the antenna feed point.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Solder the 100pF capacitor across the antenna feedpoint and the counterpoise\/ground point.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Box it up. Tune it up. Have fun!<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"768\" height=\"1024\" src=\"https:\/\/ei4hq.ie\/test\/wp-content\/uploads\/2026\/06\/E5ABDE4A-91FF-4E28-8595-977FFEEA1B3E_1_105_c.jpeg\" alt=\"\" class=\"wp-image-317\" style=\"width:500px\" srcset=\"https:\/\/ei4hq.ie\/test\/wp-content\/uploads\/2026\/06\/E5ABDE4A-91FF-4E28-8595-977FFEEA1B3E_1_105_c.jpeg 768w, https:\/\/ei4hq.ie\/test\/wp-content\/uploads\/2026\/06\/E5ABDE4A-91FF-4E28-8595-977FFEEA1B3E_1_105_c-225x300.jpeg 225w\" sizes=\"auto, (max-width: 768px) 100vw, 768px\" \/><figcaption class=\"wp-element-caption\">The EFHW from another angle, at IE-0246<\/figcaption><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">So, what&#8217;s the EFHW like in use? I humbly concede my arrogance &amp; stupidity in not accepting herd wisdom; the EFHW is a <em>wonderful<\/em> antenna for \/P activities of all sorts and is a surprisingly effective performer. Albeit I&#8217;ve only two POTA activiations with it to date <a href=\"https:\/\/ei4hq.ie\/test\/2026\/06\/12\/pota-activation-at-ie-0043\/\">IE-0043<\/a> and <a href=\"https:\/\/ei4hq.ie\/test\/2026\/06\/13\/pota-activation-at-ie-0246\/\">IE-0246<\/a>, it&#8217;s very apparent that this antenna is a keeper. The EFHW is one of those antennas that just wants to work.  It&#8217;s very tolerant of how it&#8217;s mounted and it takes mere moments to get it airborne. So far, I&#8217;ve used it only in an upside down L configuration. I&#8217;ll set it up vertically and horizontally in due course but I don&#8217;t expect any change in performance.<\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">I&#8217;m so impressed with the EFHW, that I&#8217;m building two more; a 100W 40M-10M version for &#8220;\/T&#8221; operations using 3 FT37-43 toroids for the 49:1 un-un, and a 200W 80-10M version for permanent installation at home as a secondary\/backup antenna. For that version I&#8217;ll be using 2 FT50-43 toroids for the un-un. <\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Once I&#8217;ve more use experience with all three EFHW antennas, I&#8217;ll update this post.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>My trusty 20M GP antenna, is a much-loved and proven favourite for operations away from the home QTH. Recent experience has made clear however that It&#8217;s not ideal for POTA, SOTA and other short term \/P activations. It&#8217;s relatively heavy at about 2kgs, and it takes about 15 minutes to set up. Of course, it&#8217;s [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":314,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,10,2,20],"tags":[],"class_list":["post-367","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-antennas","category-portable","category-equipment","category-pota-portable"],"_links":{"self":[{"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/posts\/367","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/comments?post=367"}],"version-history":[{"count":25,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/posts\/367\/revisions"}],"predecessor-version":[{"id":475,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/posts\/367\/revisions\/475"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/media\/314"}],"wp:attachment":[{"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/media?parent=367"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/categories?post=367"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ei4hq.ie\/test\/wp-json\/wp\/v2\/tags?post=367"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}