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RE: RE: Beginner Birds



Ok, scratch the Mode B, although I think the existing 2 meter station could
still be used if appropriate filtering (a cavity/duplexer or some such
method) is employed of the type used for terrestrial repeaters, which
receive on a single frequency just 600 kc's off from the transmit freq on a
typical installation, without desense.  And repeaters run higher power
levels than ISS does.  The only problem would be that we'd have to ship up a
new 2 meter station that would contain this filtering to ISS along with the
transponder.  

A 2 meter uplink would be easier, the cavity could be built into the uplink
receiver so that ISS's signal wouldn't desense the transponder.  

An advantage of having it inside ISS is that we wouldn't have to spend money
or weight on things such as solar cells, frames, motors, etc.  

Come on!  The technology exists!

73 de N8AU, Jim in Raymore, MO

-----Original Message-----
From: Estes Wayne-W10191 
Sent: Thursday, July 24, 2003 9:16 AM
To: Reicher, James
Subject: RE: [amsat-bb] RE: Beginner Birds 


A mode B transponder uses a 2 meter downlink that would interfere with the
existing 2m station that's used for packet, random voice contacts, and ARISS
contacts.

Wayne W9AE

-----Original Message-----
From: Reicher, James 
What about a Mode B transponder?

-----Original Message-----
From: Estes Wayne-W10191 

Robert Oler wrote:

This is where the relationship with NASA on ISS if it had any real value to 
hams would shine.  NASA should jump at the chance to put a Mode A 
transponder on the station.  Clear some hoops in terms of the paperwork 
involved, maybe even spring for some cash, and offer the launch.  With the 
new antennas the "radios/hardware" probably could even be "inside".


Wayne replies:

I like your idea of putting a ham transponder on ISS.  It would be
interesting to find out if such a payload is feasible in the foreseeable
future.

Unfortunately, a Mode A transponder on ISS probably wouldn't work well
because of interference from the 2m downlink of the ISS voice/packet
station.  As long as the ISS voice/packet/SSTV station is on 2 meters, a
transponder probably couldn't use that band for an uplink or a downlink.
When you take away 2 meters, no band pair is really attractive for a LEO
"easy sat" transponder.  The best thing that comes to mind is 435 MHz uplink
and 29 MHz downlink.  Then Doppler gets obnoxious (ISS moves really fast!),
and the transmitting equipment isn't as widely available in the third world.

A transponder on ISS may be "impossible" simply because it would render two
ham bands essentially "off limits" for any simplex operation.

Wayne Estes W9AE
Mundelein, IL, USA
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