[amsat-bb] ISS Contacts
AJ9N at aol.com
AJ9N at aol.com
Mon Apr 6 23:52:58 UTC 2015
ARISS school contacts are performed on confidential uplink frequencies and
all use the public downlink of 145.8 MHz. We incorporate multiple sets of
confidential uplink frequencies just in case the primary is experiencing
QRM. For obvious reasons, that is as much as I am going to tell you about
the uplinks. The public uplink frequencies that are posted are for general
We have had interference in the past that was accidental, some flat out
deliberate, and some that would be considered deliberate. In some parts of
the world, the 2m band is being illegally used by taxi cabs and who knows
what else. Over the course of the years, we have had to move our uplink
frequencies around due to the continued interference.
Don't forget that the ISS can hear a lot more than those of us on earth.
So what you may think is not a problem locally, could be a big time issue
for the crew. Your footprint radius may be 100 km or so; theirs is about
2400 km. They sort of have a really nice antenna height.
As for possible Field Day operation by the crew, that is anyone's guess.
We tell the crew the dates and times and it is up to them to decide whether
to participate or not. We can not make them participate. The only thing
we can suggest is to listen and if you hear the ISS on during FD, then go
for it. The same goes for just general listening. If you hear them, then
go for it. You do need to be aware of the FM capture effect and do make use
of Doppler correction. For the ARISS school contacts, we present a
proposed list of times for the schools to prioritize so that we can give them to
the ISS planners and hopefully have one get scheduled. Those times are in
the 08:00 to 19:30 UTC timeframe. So that will give you an idea of when
someone could possibly be on.
Hope this helps a bit. Just remember that ham radio is only a guest on
One of the ARISS mentors
In a message dated 4/6/2015 2:00:39 P.M. Pacific Daylight Time,
dan at post.com writes:
Info on frequencies here.
I think they also have a backup frequency that is not published. They
have had interference on both uplink and downlink in the past possibly
accidentally. The exact time of school contacts and normal downlink
frequency is usually very well advertised in the country where the
contact will take place.
Sometimes, including one recent contact in Italy they actually
re-attempted the contact at the next pass 90 minutes later as there
was interference. They try throw lots of power and gain on the uplink
in an attempt to drown out any accidental or low power interference.
On 06/04/2015, Daniel Estévez <daniel at destevez.net> wrote:
> El 06/04/15 a las 17:12, John Brier escribió:
>> fwiw, I do know not to interrupt during scheduled ARISS contacts. I
>> was telling someone else who responded to me that it was a good thing
>> they don't publish the uplink frequencies not only so people don't
>> intentionally try to take advantage of the situation, but also so
>> ignorant (and excitedly blind people like me) don't interfere.
> Sorry if this has been asked before, but are not the uplink frequencies
> 145.20 for region 1 and 144.49 for regions 2 and 3? Or do they use
> different uplink frequencies for scheduled contacts?
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