[amsat-bb] Re: HT supports full duplex satellite operation

Andrew Glasbrenner glasbrenner at mindspring.com
Tue Oct 20 10:20:17 PDT 2009

> I am thrilled with the news that AMSAT is moving forward with plans to build and launch a 1U cub sat with a U/V (Mode B) transponder. However, consistently hitting the uplink with HTs that tune no finer than 5 kHz will be a challenge. I learned that last winter when the ISS repeater was active in Mode B. When I used my FT-817 as a transmit radio and could use the main tuning dial to infinitely fine-tune the uplink, I had much better - and more consistent - success hitting the uplink than with my HT, which will only tune in 5 kHz steps.
It's all in the receiver design. The ISS D-700 isn't designed as a 
satellite receiver, and has a narrow front end.

Think of it this way. With 5 khz steps you are always within 2.5 khz of 
being "on frequency", right?

We operate the V/U FM satellites all the time without tuning the uplink, 
and that means we are up to 3 khz off, and everything works fine! So 2.5 
khz will be a piece of cake too, plus folks will hear the 2m downlink 
much easier.

73, Drew KO4MA

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