[amsat-bb] Re: Inverted-V turnstile idea

[Matthias Bopp]

Hi Matt,

are you referring to a turnstile antenna like the one available from WIMO
here in Germany ?

Please see the following link: http://www.wimo.de/download/ta1.pdf

Best regards

Matthias

www.dd1us.de


-----Ursprüngliche Nachricht-----
Von: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] Im
Auftrag von Jonny 290
Gesendet: Freitag, 28. Februar 2014 20:50
An: amsat-bb at amsat.org
Betreff: [amsat-bb] Inverted-V turnstile idea

I had an idea pop in my head for a simple turnstile antenna, and am not
finding much info on what I want to do via Google searches I wanted to
bounce this off the list and see what people think.

My idea consists of three main points:

-Antenna elements being conventional (non-folded) inverted V dipoles, tuning
the length for resonance and angle to set at 50 ohms each
-1/4 wave 50 ohm phasing line between the sets of dipoles -Feed via DK7ZB
match using a 1/4 wave paralleled 2x75 ohm line section (37 ohms),
transforming the 25 ohms back up to right around 50 ohms for final feed

This approach would give the following advantages:

-Lower SWR than standard 75-ohm parallel turnstiles -Dipoles could be
individually tuned via direct 50 ohm feed during construction -DK7ZB match
is constructed out of inexpensive 75-ohm coax -Phasing line length would
only affect phase, instead of phase and impedance.

My main question, though is: With dipole elements canted down roughly 35
degrees from vertical (what I'm ballparking to get them down to 50 ohms), am
I going to see noticeably degraded performance, especially regarding the
polarization?

Thanks for any tips or discussion!

--Matt
KC4YLV
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