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International Space Station 437.800 MHz cross band FM repeater activated

194 points| mindcrime | 5 years ago |amsat-uk.org

64 comments

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[+] segfaultbuserr|5 years ago|reply
Fun fact: There is an APRS repeater on the ISS. You can use the ISS as a relay to the APRS network. And APRS has a cellular gateway, which means you can send SMS messages to mobile phones via the ISS.

* Sending SMS Messages Through the ISS

https://www.kj7nzl.net/blog/sending-sms-messages-through-iss...

[+] ianpenney|5 years ago|reply
It’s off right now. Plans are to add a second radio in the Russian segment later so they have two IORS modules running at the same time. Then they can operate both the repeater and digipeater.
[+] ianpenney|5 years ago|reply
It’s pretty strong. You can listen to Amateur operators using it if you go to websdr.org, find one of the handful of receiving stations that cover 437.8 MHz, and time it right. One of the neat things is that you’ll easily see the Doppler shift in the spectrum waterfall.
[+] mindcrime|5 years ago|reply
I caught a little bit of traffic earlier tonight on the downlink frequency, but I wasn't able to contact anybody myself. Possibly if I'd realized the ISS was in the vicinity and gone outside earlier I would have had a shot (I only have an HT radio at the moment), but by the time I got out there they were somewhere over the North Atlantic. The ISS, if you didn't realize, moves pretty fast.

Oh well, there's always next time.

[+] tomfanning|5 years ago|reply
Sounds like you're already on it, but anyone who is thinking of trying, (1) make sure you are correctly licensed, (2) make sure you only transmit while you can clearly hear the downlink, and (3) make sure you are listening to the downlink while transmitting (full duplex) to ensure you aren't stepping on other people.
[+] bigiain|5 years ago|reply
What sort of antenna would I need to listen in with a rtl-sdr? Would I have any chance with a simple home built 1/2 wave dipole?
[+] acqq|5 years ago|reply
> The ISS, if you didn't realize, moves pretty fast.

I waited a few times to see it, and it's always just a few minutes it's visible. It orbits low and makes the full cycle around the globe in only 90 minutes.

[+] sgt|5 years ago|reply
I tuned into 437.800 MHz here in South Africa - the ISS is probably a couple of thousand km's south of here now. As I tuned in, I got morse code for 5-6 seconds. Didn't record or pick up what it was. I wonder if it was the ISS or something else.
[+] paulirwin|5 years ago|reply
Could be station identification. Many repeaters identify their call with morse code periodically.
[+] sizzzzlerz|5 years ago|reply
A sat tracking program I have shows ISS passing almost directly overhead in about 40 minutes. How would the downlink frequency vary due to doppler shift as it transits from local horizon to local horizon?
[+] tomfanning|5 years ago|reply
Short answer - by one or two of the smallest steps on a typical handheld, starting above the nominal frequency and ending below it. A bit more than that for UHF downlinks.
[+] PaulHoule|5 years ago|reply
Nice to see. The smallsat phenomenon has done very little for hams so it is nice to see the ISS facilities upgraded, also i think it is funny they can afford to build ten copies of the repeater.
[+] madarco|5 years ago|reply
What is the use case of such repeater?
[+] arghwhat|5 years ago|reply
Radio amateur experimentation and communication.

That it is cross-band is just a detail that simplifies the repeater (single-band repeaters generally use humongous filters).