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Re: Looking for Helix info



>         I'm looking for info on the G3RUH helix. I have the original article
> but looking for the details, ie diameter of turns, spacing, etc
> ...Mike WA6ARA
>
Hi Mike,
The main feature of the G3RUH design was the way James tackled the problem of matching the
helix to 50 ohm co-ax. He did this with the 1/4" strip of shim brass soldered on to the
first quarter turn of the helix element. Apart from this his design followed the normal
design rules for a helix. Number of turns depends on the purpose ... 3 or so for a dish
feed of normal f/d ratios and as long as you can if the helix is the active antenna
itself, 20 - 30 turns being average for 2.4 GHz. The diameter of the wire, diameter of the
helix winding and spacing of the turns are all calculated depending on the frequency.
There are various programs around for doing this ... I'm sure you'll get some suggestions
on this list. I use a basic program I wrote myself many years ago. I can send you a copy
if you like but the formulae are simple and are in all the antenna handbooks.
73, Bill...vk3jt
Milawa
Australia



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