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RE: RE: Beginner Birds



What about a Mode B transponder?

-----Original Message-----
From: Estes Wayne-W10191 [mailto:W10191@motorola.com] 
Sent: Wednesday, July 23, 2003 5:53 PM
To: AMSAT
Subject: [amsat-bb] RE: Beginner Birds 


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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