[sarex] Re: Future ISS amateur radio modes
bruninga at usna.edu
Wed May 2 09:06:40 PDT 2007
> Once the planned hardware is aboard and installed, having
> each system dedicated to a specific operation will minimize
> the need for mode changes and crew interaction.
But this can only be true if all systems operate with clear
isolation of all uplinks from all downlinks on separate bands.
It is impossible to have independent systems operating with
uplinks in the same band which may be used for downlinks.
Until ARISS commits to a permanent dedicated downlink band which
then guarantees other known bands for non-interfering uplink
bands, future planning is stymied by crew-required mode changes
and lack of independence of systems.
Current use of 2m for both uplink and downlink, prevents its use
by any other system for any other purpose without crew
intervention on every such use. There are really only three
1) make 2m the downlink band for simplicity of reception around
the world. Even the least advantaged country should be able to
at least borrow an ARISS UHF uplink radio for a school contact.
But it does require Doppler tuning in the blind on the uplink.
Tuning a radio +/10 KHz is not a hard skill to learn.
2) Make UHF the downlink band so that recipients can simply tune
the Doppler to best sound, and then uplink on 2m is fixed
frequency with no problems. Less interference with UHF
3) Continue status-quo, and use 2m for both uplink and downlink
for school contacts and either require crew intervention with
every mode change for use of 2 meters for anything else, or
require all other systems to not use 2m for anything, so they
can be independent of crew issues.
Until there is a permanent commitment to one of these three
possibilities, uplinks and downlinks can not be planned without
conflicts, and crew intervention is required in every mode
change on every system that might want to share 2m for anything.
Of 60+ amateur satellties, few (with more than one mode on
board) use monoband operation. There is a good reason for that.
Uplinks and downlinks are in different bands for operating
independence of modes. Just what we need on ISS.
Just a thought.
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