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Re: Stacking Circular polarized Antennas?



Luc,

I will assume you are stacking two identical helical antennas to double the
gain (i.e. you have them at the proper stacking distance).  I am not sure
what you mean by "phased vertically".  I think you mean stacked one above
the other. If so then the polarity will remain circular when pointing
directly at the satellite if the phasing lines are equal length (in-phase).

Now if one helix is wound for RHCP and the other for LHCP you will end up
with linear poalrization in some plane depending on the relative phase of
the two antennas.  If exactly zero phase angle between the two helices then
you get vertical polarity.

Signals arriving off-axis from the helical antennas will be subject to
non-circularity (ellipticity) of the antenna pattern.  Or putting it
another way, transmitting radiation off-axis will be elliptical.  If the
helix antenna were mounted on the satelllite we would call this off-axis
angle the squint angle!

Ed - AL7EB

At 10:13 PM 1/5/2003 +0100, Luc Langehegermann wrote:
>Hello,
>
>A Question... Lets say I have 2 helix antennas, and stack them perfectly 
>phased vertically. Will the pattern get in this case Elliptacally? (It 
>should) So in one direction the radiation angle will get smaller. But does 
>this stacking effect axial ratio?
>
>Thanks in advance for any explanation. 73, Luc
>
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