[amsat-bb] Re: Circular and elliptical polarization question.
domenico.i8cvs at tin.it
Wed Mar 12 14:34:27 PDT 2014
----- Original Message -----
From: "Douglas Phelps" <dphelps1 at ameritech.net>
To: "AMSAT BB" <amsat-bb at amsat.org>
Sent: Wednesday, March 12, 2014 2:10 AM
Subject: [amsat-bb] Circular and elliptical polarization question.
I read in 'The Satellite Handbook' that I can mount to linear yagis side by
side (and at right angles) and I will get elliptical polarization. My two
HI DOUG, K9DLP
IF THE ANTENNAS ARE AT RIGHT ANGLES YOU WILL GET CIRCULAR POLARIZATION AND
NOT ELLIPTICAL POLARIZATION.
1. Is their a formula or rule of thumb that will tell me how elliptical (or
non circular) the waveform will be as a factor of the separation between the
two antennas? (I would expect that the greater the separation the more
elliptical the waveform(farther from circular)).
CIRCULAR OR ELLIPTICAL POLARIZATION DO NOT DEPEND BY THE SEPARATION OF TWO
IDENTICAL ANTENNAS BUT MORE IS THE GAIN OF THE ANTENNAS AND MORE THE
SEPARATION YOU NEED.
2. I would think that the closer the better. I know when you mount two yagis
next to each other, in the same plane, there is a minimum separation
distance to prevent the antennas from affecting each other but with cross
polarization intending circular polarization, the closer the better. Does
this make sense?
NO ! CIRCULAR OR ELLIPTICAL POLARIZATION DEPENDS ONLY FROM THE POINT OF VIEW
THAT YOU LOOK AT THE LOBE RADIATED BY THE ANTENNA .
IN A SEPARATE EMAIL I HAVE SENT TO YOU THE ARTICLE "THE ADVANTAGES OF
CIRCULAR POLARIZATION" BY K4KJ THAT EXPLAINS THE ABOVE:
AS AN EXAMPLE, IF YOU STAND IN FRONT OF A FULL PHONOGRAPH RECORD DISK YOU
WILL LOOK A FULL CIRCLE (CIRCULAR POLARIZATION) BUT IF YOU ROTATE SLOWLY THE
DISK BY 90° YOU WILL LOOK AT FIRST AN ELLIPSE (ELLIPTICAL POLARIZATION) AND
THAN A STRAIGHT VERTICAL LINE (LINEAR VERTICAL POLARIZATION)
73" DE i8CVS DOMENICO
The reason I am asking is that I want to mount arrow antennas with the same
element sets at right angles and offset a quarter wavelength, with the
correct phasing harness and the WRAPS AZ/EL to create a portable auto
tracking satellite setup that can be disassembled and easily moved. Yes, I
know the VHF offset will be wrong for UHF but I intend to re-drill the UHF
antenna holes so that both the VHF and UHF will be offset a quarter
The matching system used by arrow does not allow the crossing of the same
wavelength antenna on the same boom.
I would appreciate and advice from those that are more competent with
antenna theory than myself.
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