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Re: sts-93 contact

This frequency problem is a very old and touchy subject.
Many of the terrestrial bound people who have suggested frequencies for
Mir and ISS, prefer to suggest different channels for different parts of the

My point has always been, that the crews are too busy to keep looking at a
computer to know when they should change channels.  In space there are no
So why do we need to make Radio borders.
This is why we at MAREX-NA have always opposed using different public channels
for Mir
depending on where the space station is located.  The primary public channel for
Mir 145.985 FM simplex
was picked by myself specifically so the crew would not have to change channels.
And guess what,  it works world wide.  One channel, Simplex, Simple and no

The STS-93 mission is an example of a frequency selection plan, which did not
ISS will need to be on a stable frequency, you can not have the crew constantly
channels as they fly around the world at 17, 500 mph in 92 minutes.

New Topic:

ISS frequency challenge:

The proposed  channels for ISS are:
145.8000 down link primary
145.8125 down link backup
145.9900 down link backup

Note the odd-ball channel 145.8125, it is a 12.5k channel step.

The ISS uplinks proposed are:
144.4900 primary uplink
144.4700 backup uplink
144.4500 backup uplink

Now here is the challenge:
Try to program the down link channel 145.8125 into a memory channel
with ANY one of the Uplink channels.
As you will find, 99% of all Amateur Radio 2-meter radio made today
can not store that frequency combination into memory.

RX        TX
145.8125  144.450
145.8125  144.470
145.8125  144.490

Only a few radios which have two VFO can support this combination, however
most can not save the combination into a Memory location.

Good luck

"Bruce Paige" <kk5do@AMSAT.Org> on 08/04/99 05:37:28 PM

Please respond to kk5do@AMSAT.Org

To:   sarex@AMSAT.Org
cc:    (bcc: Miles Mann/PicTel)
Subject:  [sarex] sts-93 contact

we had the opportunity to talk to n5sub yesterday on the houston amsat net.
we asked how he made his contact with the shuttle when it seemed many of
us were unsuccessful.

turns out that for the pass over houston, he was transmitting on 144.49 (the
frequency for packet and voice over europe). that is where the shuttle crew
was listening, not on 144.45 or 144.47. seems they would turn the robot off
and forget to change the frequency. that is why they never heard anyone
return to them.

personally, i had not even thought that that would have happened or i would
have switched over to 144.49 myself and given it a try just for grins.

oh well, you never know.


Bruce Paige, KK5DO                         Internet: kk5do@amsat.org
Houston, Texas                                   or: kk5do@hal-pc.org
AMSAT Area Coordinator
ARRL Awards Manager (WAS, 5BWAS, VUCC), VE
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