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Re: Polarization of HAMSAT downlink



Hi William, PE1RAH

I already anticipated to you that following my observations 
the polarization of downlink for HAMSAT is LHCP in 2 meters.

I am fortunate enough because I can switch between LHCP and 
RHCP in 2 meters but those using crossed yagi with only RHCP
i.e. the majority of us are suffering a penalty of more than 20 dB 
with HAMSAT because they don't have a linear polarization 
capability.

In addition they cannot lover the antennas and reverse the polarization
because RHCP is needed for the uplink/downlink of other satellites. 

Beginning with OSCAR-6 the standard polarization for AMSAT
was RHCP for the benefit of all according to the IEEE definitions

I cannot understand why AMSAT-India and ISRO made just the
opposite but I hope there is a good technical reason for it.

Best 73" de

i8CVS Domenico
          
----- Original Message ----- 
From: "William Leijenaar" <pe1rah@yahoo.com>
To: <amsat-bb@AMSAT.org>
Sent: Thursday, June 30, 2005 7:28 PM
Subject: [amsat-bb] Polarization of HAMSAT downlink


> Hi AMSATs,
> 
> I was away for a few days and arrived back home
> yesterday. When I checked my email I see an answer
> from ISRO on my question to confirm the polarization.
> 
> I think I remembered that it was said to be RHCP, but
> this is wrong... 
> 
> ISRO confirmed in the email to me that the downlink of
> HAMSAT is LHCP. They advise to use linear antennas to
> avoid fluctiations in downlink signal level due to
> polarization changes. The downlink is strong enough to
> overcome the 3dB losses you have with a linear antenna
> to an circular antenna.
> 
> About the uplink they didn't mention. I request them
> also to confirm about the downlink polarization.
> When I get the answer I will post it...
> 
> 73 
> William
> PE1RAH
> ---
> ----
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----
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