----- Original Message ----- From: "Douglas Phelps" dphelps1@ameritech.net To: "AMSAT BB" amsat-bb@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 questions are:
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 wavelength.
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.
Doug K9DLP _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb