Hi all,

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 contacts.

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 the ISS.

73, Charlie AJ9N One of the ARISS mentors

In a message dated 4/6/2015 2:00:39 P.M. Pacific Daylight Time, dan@post.com writes: Info on frequencies here.

http://www.ariss.org/contact-the-iss.html

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@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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