[amsat-bb] RH or LH ??

[Hasan al-Basri]

Excellent Post, Jim and brings back some wonderful memories.
73, N0AN
Hasan


On Wed, Mar 25, 2020 at 9:08 AM James Jipping via AMSAT-BB <
amsat-bb at amsat.org> wrote:

> Good Morning!  Just reviewing some past email and the topic of which
> polarization "RH or LH ?" showed up.
>
> It must have been close to a solar activity maximum that I started my
> satellite adventure.  Faraday rotation was in full swing (or should I
> say "rotation").  It was a phenomenon we all experienced and had to deal
> with.
>
> My first antenna project included a polarization switch  and I have
> always had one on my satellite antennas.  My arrow linear polarized
> antenna has one  (my arm/wrist rotation device).  I would like to advise
> that if you can manage it (financially or creatively -- "in the good old
> days it was creatively")  to include some way of changing the
> polarization plane or direction of both the transmitted and received wave.
>
> ALL signals WILL experience some amount of polarization depending on the
> strength of the earth's magnetic field strength IN THE PATH of the
> signal from station to satellite (and vice/versa).  The total rotation
> effect is constantly changing.  And do not forget the effect that the
> earth's ionosphere has on polarization.  As we know, the ion density of
> the ionosphere, is constantly changing.  Right now that effect is at
> it's minimum as the sun's sunspot activity is at it's minimum.  IT WILL
> change and the effect will really begin to be noticed.
>
> Please remember that the entire effect is proportional the total
> magnetic and ion densities, so the rotation is not going to be 90
> degrees or 180 degrees.  We will not always get RH OR LH, vertical OR
> horizontal.  If the right conditions exist a RH signal could actually
> turn into a linear signal.
>
> Another factor to consider is the degree of rotation is proportional to
> the square of the wavelength. The effect is noticed at UHF frequencies,
> so for the many satellites whose uplink is UHF there is an effect but as
> we go to higher frequencies rotation effects become less a problem.
> Imagine the fun we had with mode A satellites in the beginning. All 10
> meter down link and 2 meter up link and the Sun was doing it's sunspot
> thing.
>
> Well that's PHYSICS lesson for the day.  It's been a while that I could
> do that.
>
> My advice for the day ---  get a switch!  You are going to need it. I
> always find, even now, that a switch in polarization at the antenna is
> needed to maintain a good QSO.
>
> Have a good day, at home or where you have to be,
>
> Jim Jipping, W8MRR
> AMSAT # 5512
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
> expressed
> are solely those of the author, and do not reflect the official views of
> AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
>