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Boas.<br>
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O colega Gomes, como vai funcionar no mínimo 10 x pior que o velhinho (passo em frente) qualquer cabo serve.<br>
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Quem não tem que fazer faz antenas J.<br>
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Pinto<br>
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CT1ANO<br>
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..<br>
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Obter o <a href="https://aka.ms/ghei36">Outlook para Android</a></div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> cluster-bounces@radio-amador.net <cluster-bounces@radio-amador.net> on behalf of Gomes <ct1hix@sapo.pt><br>
<b>Sent:</b> Monday, August 5, 2019 12:28:02 PM<br>
<b>To:</b> Resumo Noticioso ARLA/CLUSTER <cluster@radio-amador.net><br>
<b>Subject:</b> Re: ARLA/CLUSTER: Antena J para os 10m simples</font>
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<p>Bom dia<br>
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<p>Acho piada a estes esquemas onde se usam cabos coaxiais... x cm, y comprimento mas nunca se refere o factor de velocidade do cabo usado e depois dá asneira.
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<pre class="moz-signature" cols="72">73, Gomes op: CT1HIX
<a class="moz-txt-link-freetext" href="https://ct1hix.net/">https://ct1hix.net/</a></pre>
<div class="moz-cite-prefix">Às 11:14 de 05/08/19, João Costa > CT1FBF escreveu:<br>
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I'm trying to build a 1/2 wave "Coaxial J-Pole" 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)" moz-do-not-send="true">here</a>:</p>
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<img alt="Coaxial
J-Pole" style="margin: 0px; padding: 0px; border: 0px;
font-style: inherit; font-variant: inherit;
font-weight: inherit; font-stretch: inherit;
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max-width: 100%;" moz-do-not-send="true" src="https://i.stack.imgur.com/D2EMX.jpg"></p>
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Such an antenna would be great for stringing up in a tree when operating remotely, no tuner needed.</p>
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The trick is that I'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>
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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't match the feed point impedance.</p>
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Succinctly: How can I calculate the physical parameters of a single-stub impedance transformer when the matching section impedance doesn't match either the feed point impedance or the load impedance?</p>
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