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Re: AMSAT-BB Digest, Vol 3, Issue 239



Ron,

Been there, Done that.  I am using a Directive Systems Looper antenna for 
1.2 GHz.  With the setup I have, I chose a 6 foot long version with a 30 
degree beamwidth rather than the 12 foot long antenna.  It works quite well 
when AO-51 is put in L/U mode as was done several months back for channel B. 
You can check out my satellite antenna setup on QRZ.

I am using the IC-910 with the 1.2 GHz module.  Works great.  Figure about 
half of your output will ever reach the antenna.  I selected Belden 9913F7 
ultraflex cable which is ideal for my installation.  Keep the runs as short 
as possible.  Probably better, if it works for you, would be LMR-400 or 600 
or hardline.

For a given length CP Yagi, the gain of the antenna is going to increase as 
the frequency increases (more elements, etc) and beamwidth of the antenna is 
going to become more narrow.  So pointing the antenna accurately becomes a 
more significant  factor.  It's time to go out and buy the elevation rotor. 
You'll find that it is worth every penny you put into it.  A beamwidth of 30 
degrees on 1.2 GHz gives the half power points as 15 degrees either side of 
the antenna position.  You don't really want to be 15 degrees off.  You want 
to keep the satellite well within the main lobe of the antenna.  At 1.2 GHz, 
starting with 10 watts, figure half of that gets to the antenna.  You don't 
want to throw away half or all of what's left because the antenna isn't 
pointed at the satellite.  Elevation control will also reduce your power 
requirements on all of your uplinks.

Date: Sun, 11 May 2008 20:49:23 -0500
From: Ronald Nutter <rnutter@networkref.com>
Subject: [amsat-bb]  Suggestions for Mode L antenna
To: amsat-bb@amsat.org
Message-ID: <4827A223.6020304@networkref.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I am considering purchasing the 1.2 ghz module for my IC-910H.  For my
satellite work, I have my antennas angled at about 20 degrees since I
dont have an az/el rotor.  This setup worked reasonably well with Mode S
this weekend.  What are my chances to be able to work Mode L with this
kind of setup ?  Also, I would appreciate any suggestions for an antenna
that I could use.  With only 10 watts, I am not expecting a great signal
but I would hope to have at least a readable signal.  Also, would
appreciate any suggestions as to coax/feedline that I should look at
buying ?

Thanks,

Ron
KA4KYI

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