[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

RE: Echo Antenna Polarity



A clarification on ECHO:   Signals coming from ECHO 
will be RHCP and sometimes LHCP on one transmitter
LHCP and sometimes RHCP on the other

Trying to receive with either a RHCP or LHCP
will require frequent switching to always find what
is best at any given geometry or transmitter.  And
there will be deep nulls if the wrong one is used
at the wrong time.

LINEAR will give up 3 dB under ideal conditions.
but will -not- see total fades and will always be
within 3 dB of optimal for all conditions on all
transmitters...     Bob


>>> "Rick Hambly (W2GPS)" <w2gps@cnssys.com> 7/5/04 1:16:03 AM >>>
Art,

Having both polarities available at your station would be ideal but is
not
necessary.  As Bob Bruninga pointed out earlier this evening, linear
polarization would work fine with only 3db degradation over the ideal.
In
the Northern mid-latitudes (the US 48 states) you will never be even
close
to looking down the bore sight anyway. 

Rick
W2GPS
AMSAT LM 2232


-----Original Message-----
From: KC6UQH [mailto:kc6uqh@cox.net] 
Sent: Monday, July 05, 2004 1:10 AM
To: Rick Hambly (W2GPS); 'Bill Ress'
Cc: amsat-bb@AMSAT.Org 
Subject: Re: [amsat-bb] Echo Antenna Polarity

Rick,
In the past with LEO's, the antenna pointing angle could sometimes 
require
both polarity's. This could happen every orbit or may remain stable
for
months dependent on the pointing angle of the antennas on the
spacecraft.
 As Echo has both polarities for isolation, am I correct in assuming
that
both polarities are necessary, will change with pointing angle, and
linear
antennas will not work if both transmitters are operating at the same
time?

Art, KC6UQH
----- Original Message -----
From: "Rick Hambly (W2GPS)" <w2gps@cnssys.com>
To: "'Bill Ress'" <diskdrives@ieee.org>
Cc: <amsat-bb@AMSAT.Org>
Sent: Sunday, July 04, 2004 2:32 PM
Subject: RE: [amsat-bb] Echo Antenna Polarity


> Bill,
>
>-------------CUT-------------



----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the
author.
Not an AMSAT member? Join now to support the amateur satellite
program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home