[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Turnstile antennas

I was think on homebrewing this antenna and putting it on the roof 
(Metal mobilehome) at a 1/4 wave length. I do have a clear area from 
east to south west, I have trees in other directions, but there are bare 

he uses it for ARDF.

I'll be using it for ISS, AO-27, and the FM birds.
I hope it works ok.

73 Shawn, N3ZWW

John wrote:

>							24 February 2005
>	N3ZWW de G3BVU/W1   BT
>At 01:59 2/24/05 -0500, you wrote:
>>Just wondering how good are Crossed-dipole (Turnstile antennas)
>	+++++++++++++++++++++++++++++++++++++++++++++++++++++++
>	Shawn,
>	First a note about the Turnstyle antenna.
>	A Turnstyle antenna consists of a pair of crossed dipoles PLUS a pair of
>reflector elements spaced about quarter wavelength below (behind) the
>driven pair. Without the reflectors, the pair of crossed dipoles are known
>simply as "crossed dipoles".
>	A Turnstyle antenna is an excellent antenna for LEO, Polar orbit,
>satellites. Like all antennas it should be installed "in the clear". I have
>used one for over a dozen years for receiving the 137MHz weather satellite
>image signals. I start receiving image data within a few seconds of the
>satellite crossing my AOS horizon and continue to receive image data until
>a second or two after LOS! No one can ask for more than that. Here in New
>England, I get image data from south of Cuba to North of Hudson Bay!
>	As noted above, the secret is to get the Turnstyle up above all local
>obsticles. Install it as high as you can.
>	An even "better" omni-directional antenna for LEO satellite work is the
>Quadrifilar Helix. This gives equal coverage to the Turnstyle and has the
>added advantage of maintaining its circular polarisation property over the
>total hemi-sphere, from horizon to horizon in all direction, and over all
>elevation angles.
>	The Turnstyle, as noted above, is good. However it is only circular
>polarised at the zenith (directly overhead). At the horizon it is linear,
>horizontal, polarised. It is elliptically polarised, of varying ratios, at
>all intermediate elevation angles.
>	Summary:
>	The Turnstyle is VERY GOOD, the Quad Helix is EXCELLENT.
>	73s,   de John  G3BVU/W1   amsat 439.
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org