<div dir="ltr"><span class=""><div class="gmail-votecell gmail-post-layout--left" style="margin:0px;padding:0px 15px 0px 0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,&quot;Helvetica Neue&quot;,Helvetica,sans-serif;font-size:13px;vertical-align:top;box-sizing:inherit;width:auto;color:rgb(36,39,41)"><div class="gmail-js-voting-container gmail-grid gmail-fd-column gmail-ai-stretch gmail-gs4 gmail-fc-black-200" style="padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;display:flex;color:rgb(187,192,196)"><div class="gmail-js-vote-count gmail-grid--cell gmail-fc-black-500 gmail-fs-title gmail-grid gmail-fd-column gmail-ai-center" style="margin:2px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;display:flex;font-size:1.61538rem;color:rgb(106,115,124)"><br><br></div></div></div><div class="gmail-postcell gmail-post-layout--right" style="margin:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:Arial,&quot;Helvetica Neue&quot;,Helvetica,sans-serif;font-size:13px;vertical-align:top;box-sizing:inherit;width:auto;min-width:0px;color:rgb(36,39,41)"><div class="gmail-post-text" style="margin:0px 0px 5px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:1.3;font-size:15px;vertical-align:baseline;box-sizing:inherit;width:676px"><p style="margin:0px 0px 1em;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">I&#39;m trying to build a 1/2 wave &quot;Coaxial J-Pole&quot; antenna, similar to what is described <a href="http://members.upc.nl/a.vrijswijk/documents/42.html" rel="nofollow noreferrer" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;color:rgb(44,87,119)">here</a>:</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both"><img src="https://i.stack.imgur.com/D2EMX.jpg" alt="Coaxial J-Pole" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; line-height: inherit; font-family: inherit; vertical-align: baseline; box-sizing: inherit; max-width: 100%;"></p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">Such an antenna would be great for stringing up in a tree when operating remotely, no tuner needed.</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">The trick is that I&#39;m trying to use 75Ω RG6 coax for the matching section (because it is relatively inexpensive and low-loss), but I want a 50Ω impedance at the feed point.</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">There are many single-stub matching network calculators, but almost all of them assume that the impedance of the matching network is the same as the feed point impedance. I know that such a matching network is possible because that is exactly what the traditional j-pole antenna is: a single-stub impedance transformer feeding a half-wave antenna, where the matching section impedance doesn&#39;t match the feed point impedance.</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;clear:both">Succinctly: How can I calculate the physical parameters of a single-stub impedance transformer when the matching section impedance doesn&#39;t match either the feed point impedance or the load impedance?</p></div><div class="gmail-post-taglist gmail-grid gmail-gs4 gmail-gsy gmail-fd-column" style="padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:in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