
International Space Station 437.800 MHz cross band FM repeater activated - mindcrime
https://amsat-uk.org/2020/09/02/iss-fm-repeater-activated/
======
segfaultbuserr
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...](https://www.kj7nzl.net/blog/sending-sms-messages-through-iss/)

~~~
ianpenney
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.

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ianpenney
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.

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mindcrime
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.

~~~
bigiain
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?

~~~
signaturefish
I believe you can hit it with an HT, although the Youtube videos I've seen of
doing it have been an HT with a hand-held Yagi cabled in in place of the usual
whip antenna. A resonant dipole would probably pick it up - as others have
said, the signal's fairly powerful.

Satellite comms is something I want to play with, personally, so I welcome
this news. Need to get my Foundation license (UK) before I can go two-way,
though.

~~~
jimnotgym
Go for it! It really isn't hard, it just requires a small amount of
application.

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sgt
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.

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paulirwin
Could be station identification. Many repeaters identify their call with morse
code periodically.

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arghwhat
To elaborate: It's a requirement that amateur radio stations periodically
identify themselves by the operator callsign during transmission. For unmanned
stations like repeaters this is usually accomplished with an automatic morse-
code transmission of its callsign.

The transmission occurs if the repeater has been activated, usually every 10
mins or so after a moment of silence, or after a longer period of silence,
whichever comes first.

(The repeater users still have to identify themselves with their own callsign
during use of a repeater.)

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geocrasher
I am personally quite excited about this and look forward to giving it a try.
A simple homemade antenna is all that's needed, and they're not expensive to
make:

[http://ve2zaz.net/Arrow_Ant/Arrow_Style_Ant.htm](http://ve2zaz.net/Arrow_Ant/Arrow_Style_Ant.htm)

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sizzzzlerz
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?

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oliveshell
Good question. Some info on tuning for Doppler shift:

[https://www.qsl.net/ah6rh/am-radio/spacecomm/doppler-and-
the...](https://www.qsl.net/ah6rh/am-radio/spacecomm/doppler-and-the-iss.html)

~~~
sizzzzlerz
Thank you, that was very informative. Seems like the calculations are pretty
straight forward. I need to see if I can create my own charts like that.

~~~
nickysielicki
The open source software gpredict can do this live for you.

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PaulHoule
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.

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madarco
What is the use case of such repeater?

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arghwhat
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).

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082349872349872
Is the highly non-stationary nature of the repeater an interesting part of the
experimentation?

[http://images.spaceref.com/news/2003/speedlimit.jpg](http://images.spaceref.com/news/2003/speedlimit.jpg)

~~~
arghwhat
Of course. You'll have to adjust for the Doppler shift (about 7kHz swing
during a pass IIRC), and depending on your antenna design you might have to do
precise tracking during the pass.

There are also sub-sports such as QRP that tries to perform communication
using very low power levels, which makes everything much more challenging,
including the already slightly tricky contact with the ISS. I believe the
current QRP record is 1.6 _billion_ miles-per-watt, with 1 _micro_ watt making
it from Oregon to Alaska (1650 miles).

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dano
These radios are built by a retired Qualcomm engineer in La Mesa California

[https://www.cbs8.com/article/news/local/zevely-zone/la-
mesa-...](https://www.cbs8.com/article/news/local/zevely-zone/la-mesa-man-
building-space-radios-from-his-
garage/509-445801a4-aaf2-419b-8758-f423d8333a04)

