[sarex] Re: Future ISS amateur radio modes

Ransom, Kenneth G. (JSC-OC)[BAR] kenneth.g.ransom at nasa.gov
Wed May 2 10:20:53 PDT 2007

Looks like option 3 would work with the eventual 28, 145, 430 and 2400
MHz options planned for installation. That will provide 4 bands for 4
different modes.

Keep in mind that the primary goal is to support school contacts.
Keeping them on 2 meters greatly simplifies the task for a lot of first
timers working a space based radio station. Additional objectives must
fall in line with that goal.

Another difference is that the ISS is setup more like a club station
than a satellite. Future enhancements could convert it into a more
satellite-ish operation but we have a lot of those orbiting already.

Kenneth - N5VHO

-----Original Message-----
From: sarex-bounces at AMSAT.Org [mailto:sarex-bounces at AMSAT.Org] On Behalf
Of Robert Bruninga
Sent: Wednesday, May 02, 2007 11:07 AM
To: sarex at AMSAT.Org
Subject: [sarex] Re: Future ISS amateur radio modes

> 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 choices...

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 radars...

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

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.
Bob Bruninga

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