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Re: psk31 on satellite question



PSK31 has to be within a few Hz to work.  But we solved
most of the +/- 9,000 Hz doppler (UHF) by operating the
uplink on 10m (+/- 600 Hz) and then bringing the downlink
down on FM so there is no downlink doppler on the tones
on PCSAT2, RAFT and ECHO...

A better way would be a pair of tethered cubesats, operating
as an "in-band-repeater.... Uplink on 28.120 and downlink
on 29.4 and with an inverting transponder, the Doppler would
only be about 20 Hz through the entire pass...  de WB4APR, Bob

>>> "William Leijenaar" <pe1rah@hotmail.com> 4/10/04 12:09:10 PM >>>
Hi AMSATs,

I am looking for some way to have a digital communication via satellite

under extreem conditions and without doppler tracking from the ground 
station side.

The modulation type like psk31 is very interresting, but the problem is
the 
doppler frequency tracking. I am not so familiar with psk31, but maybe

somebody knows if there is a system that automaticaly corrects the
doppler 
effect, so that the ground station can be on one fixed frequency...

Propably these systems are slow (it takes some time to lock)  maybe
somebody 
has info about that ?

Kind regards,

William PE1RAH
---

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