Re: [amsat-bb] GRRRRRRRRRRR!

["John / NS1Z" <ns1z@xxxxxxxx>]

But not likely to the extent one would experience by using the opposite
polarity, say LHCP to RHCP? I can envision the received (I think that is
what you meant to say) signal not being 'perfectly' circular in either pole,
as seen by my linear antenna. However, I cannot imagine that lack of perfect
circularity ever approaching a true linear polarity. This is where I should
think the greatest signal attenuation would occur. I know opposite polarity
isolation can be as great as 20 dB for linear (Vertical to Horizontal)
antennas. Anyone have info on LHCP to RHCP isolation? Is it identical? Why
do they use it on International satellites and Linear on Domestic?

Crikey! If we're not careful we're all gonna learn something!

I have been using linear antennas for the last 6-7 years. Changed when the
last "polarity switching relay" gave out on the circular antennas I had up.
These relays are always under-rated and short lived! I also noticed I didn't
experience the "whoop whoop" of the signal due to polarity rotation that
some operators seem to experience. This is, I imagine that's what causes
them to speak in those halting dialogs. 8-0=

Anyway, it works for me and I have found no compelling reason to spend more
for the circular. Again, based on my experiences. Your mileage may vary - I
get 42mpg with my Saturn SC2...........

----- Original Message -----
From: Jon Ogden <na9d@mindspring.com>
To: John / NS1Z <ns1z@arrl.net>; <amsat-bb@amsat.org>
Sent: Friday, March 02, 2001 12:06 AM
Subject: Re: [amsat-bb] GRRRRRRRRRRR!


> on 3/1/01 3:21 PM, John / NS1Z at ns1z@arrl.net wrote:
>
> > Hmmmmm!!??? Wouldn't you have to spin that Arrow antenna pretty fast to
> > achieve circular polarization? The best (?) approach is to use linear
> > polarization. Your signal is down 3 dB but the fade due to polarity
changes
> > is non-existant.....
>
> Not really correct, John.
>
> If the CP signal you receive is PERFECTLY circular, then yes, you'll only
be
> 3 dB down.  HOWEVER, most of the time your signal will be elliptically
> polarized one way or another.  That means that if your linear antenna is
> orthogonal to the main part of the ellipse, then you have much worse than
a
> 3 dB drop depending on the eccentricity (I think that's the right word) of
> the ellipse.
>
> So yes, you still could get fades with a linear antenna and you most
likely
> will.
>
> 73,
>
> Jon
> NA9D
>
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> Member:  ARRL, AMSAT, DXCC, NRA
>
> http://www.qsl.net/ke9na
>
> "A life lived in fear is a life half lived."
>

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