ARLA/CLUSTER: Antena J para os 10m simples

[Durval Pinto]

Boas.
O colega Gomes, como vai funcionar no mínimo 10 x pior que o velhinho (passo em frente) qualquer cabo serve.
Quem não tem que fazer faz antenas J.
Pinto
CT1ANO
..


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From: cluster-bounces  radio-amador.net <cluster-bounces  radio-amador.net> on behalf of Gomes <ct1hix  sapo.pt>
Sent: Monday, August 5, 2019 12:28:02 PM
To: Resumo Noticioso ARLA/CLUSTER <cluster  radio-amador.net>
Subject: Re: ARLA/CLUSTER: Antena J para os 10m simples


Bom dia

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.

73, Gomes op: CT1HIX
https://ct1hix.net/

Às 11:14 de 05/08/19, João Costa > CT1FBF escreveu:



I'm trying to build a 1/2 wave "Coaxial J-Pole" antenna, similar to what is described here<http://members.upc.nl/a.vrijswijk/documents/42.html>:

[Coaxial                    J-Pole]

Such an antenna would be great for stringing up in a tree when operating remotely, no tuner needed.

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.

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.

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?

antenna-theory<https://ham.stackexchange.com/questions/tagged/antenna-theory> impedance<https://ham.stackexchange.com/questions/tagged/impedance> coaxial-cable<https://ham.stackexchange.com/questions/tagged/coaxial-cable>



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