8 ms·

International Space Station 437.800 MHz cross band FM repeater activated

194 points by mindcrime 6y ago

mindcrime 6y ago
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 6y ago
  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?
  - GekkePrutser 6y ago
    Yes I've received it on a portable even. For a satellite it's easy probably because they're so close (LEO) and have plenty of power too burn.
    - tomfanning 6y ago
      Yeah, it's a lightly modified Kenwood mobile VHF/UHF set typically used in a car. Model D710GA. Stock it's a 50W radio, though can be run at 5W. Cube sats have around the hundreds of milliwatts. So yes, much higher power than a cube sat.
      - mindcrime 6y ago
        Some more info on the equipment being used: https://www.jvckenwood.com/en/press/2020/03/press_200313_2.html https://www.jvckenwood.com/en/press/2020/03/press_200313_2.h...
      - deleted 6y ago
        [deleted]
  - mindcrime 6y ago
    I was able to hear some of the traffic using my Baofeng F8HP with a stock rubber ducky antenna, so you don't need much on the receive side. At least when the ISS is close to you. Not sure what the window is as far as how far removed it can be from directly overhead, and yet still be able to receive that signal with a small antenna like that. What it takes to hit the repeater I'm less sure. I've heard it can be done with an HT like mine, but I'm guessing that's only possible when it's directly overhead, or very near so. That said, I'd be happy to find out that I'm wrong about that.
  - signaturefish 6y ago
    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 6y ago
      Go for it! It really isn't hard, it just requires a small amount of application.
  - tmostak 6y ago
    Definitely can pick it up with a HT, just caught it for ~3 minutes in the Bay Area on a Baofeng HT with whip antenna, and even picked up the first part while I was still indoors. There was a lot of static although I could make out some of the sentences.
    - signaturefish 6y ago
      Wow, that's a stronger signal than I thought. Maybe I'll give it a go with a whip the next time the ISS passes over me.
  - tomfanning 6y ago
    For listening, a QFH antenna is ideal for LEO objects. It's typically made of copper pipe or the braid of stiff coax.
  - jimnotgym 6y ago
    Absolutely you will do well with a dipole.
- acqq 6y ago
  > 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.
  - Shacklz 6y ago
    For those curious when and where to look to see the ISS by eye only: https://james.darpinian.com/satellites/ https://james.darpinian.com/satellites/ The site is incredibly awesome and helped me see the ISS (and other satellites) quite a few times already!
    - Moru 6y ago
      Stellarium is great for this too.
  - sgt 6y ago
    I recommend the app ISS Spotter by Martin van Mierloo.
  - tomfanning 6y ago
    A 90 degree pass (overhead) is around 10 minutes. And obviously for radio, it doesn't need to be visible (reflecting sunlight), just ~above the horizon.
    - acqq 6y ago
      > A 90 degree pass (overhead) is around 10 minutes. Yes, that's approximately what I remember. The path of ISS is created with the goal that ISS doesn't fly over the same pieces of land or sea. Instead, it takes a lot of orbits before I can see it crossing exactly over my location, giving me around 10 minutes when that cross is ideal, otherwise, it's less, if the current path is close enough at all. Seeing is of course limited more than obtaining a radio signal, as to see ISS it has to fly above you at the time that the sun can reflect from it, and to have clear skies. One doesn't need that to catch just a radio signal, but the ISS path should still be such that it's close to your location, and the time during the FM signal can be received will still be short.
- tomfanning 6y ago
  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.
  - mlyle 6y ago
    > (3) make sure you are listening to the downlink while transmitting (full duplex) to ensure you aren't stepping on other people. If possible. Not everyone has fancy-pants cross-band full duplex capability. I know a couple HTs will do it now, but this is still a bit exotic. This is the strongest space amateur FM repeater ever; surely those of us who are better equipped can use SO-50, etc, without issue, and we shouldn't get too mad if there's a little less-than-ideal operation on something as newbie-friendly as this.
    - dx4100 6y ago
      My cheapest HT can do this. And my 20 year old radio can do it. So not sure about "exotic"
      - jimnotgym 6y ago
        What radios are they?
        nickysielicki 6y ago
        Kenwood's TH-D72, TH-V71A, and TM-D710G can do it. An incomplete list of full duplex vhf/uhf cross-band FM radios can be found in this reddit comment: https://www.reddit.com/r/amateurradio/comments/97jhik/getting_into_satellites_need_full_duplex_uhfvhf/e48mxpf/?context=3 https://www.reddit.com/r/amateurradio/comments/97jhik/gettin...
        jimnotgym 6y ago
madarco 6y ago
What is the use case of such repeater?
- arghwhat 6y ago
  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).
  - 082349872349872 6y ago
    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 6y ago
      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 microwatt making it from Oregon to Alaska (1650 miles).
  - prox 6y ago
    But if the ISS passes over in just a few minutes, is that useable?
    - arghwhat 6y ago
      You have a ~10 minute window every ~90 minutes IIRC. The HAM sport is mostly about establishing contacts of increasing difficulty, not about making boring, rock-solid reliable communication links. 10 minutes is plenty for that, and helps stop people trying to hog the thing as only one person can be received at a time. Outside experimentation (e.g. trying an antenna, transmitter or receiver design), the HAM radios on the ISS are also used for school-astronaut contacts.
PaulHoule 6y ago
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.
sgt 6y ago
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 6y ago
  Could be station identification. Many repeaters identify their call with morse code periodically.
  - arghwhat 6y ago
    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.)
geocrasher 6y ago
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
sizzzzlerz 6y ago
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?
- oliveshell 6y ago
  Good question. Some info on tuning for Doppler shift: https://www.qsl.net/ah6rh/am-radio/spacecomm/doppler-and-the-iss.html https://www.qsl.net/ah6rh/am-radio/spacecomm/doppler-and-the...
  - sizzzzlerz 6y ago
    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 6y ago
      The open source software gpredict can do this live for you.
- tomfanning 6y ago
  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.
segfaultbuserr 6y ago
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 6y ago
  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.
- jbj 6y ago
  Apparently there is a non profit that relays some of those messages via satellite: http://forums.othernet.is/t/aprs-outnet-on-outernet/2620 http://forums.othernet.is/t/aprs-outnet-on-outernet/2620
ianpenney 6y ago
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.
dano 6y ago
These radios are built by a retired Qualcomm engineer in La Mesa California https://www.cbs8.com/article/news/local/zevely-zone/la-mesa-man-building-space-radios-from-his-garage/509-445801a4-aaf2-419b-8758-f423d8333a04 https://www.cbs8.com/article/news/local/zevely-zone/la-mesa-...

194 points by mindcrime 6y ago

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 6y ago
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?
- GekkePrutser 6y ago
  Yes I've received it on a portable even. For a satellite it's easy probably because they're so close (LEO) and have plenty of power too burn.
  - tomfanning 6y ago
    Yeah, it's a lightly modified Kenwood mobile VHF/UHF set typically used in a car. Model D710GA. Stock it's a 50W radio, though can be run at 5W. Cube sats have around the hundreds of milliwatts. So yes, much higher power than a cube sat.
    - mindcrime 6y ago
      Some more info on the equipment being used: https://www.jvckenwood.com/en/press/2020/03/press_200313_2.html https://www.jvckenwood.com/en/press/2020/03/press_200313_2.h...
    - deleted 6y ago
      [deleted]
- mindcrime 6y ago
  I was able to hear some of the traffic using my Baofeng F8HP with a stock rubber ducky antenna, so you don't need much on the receive side. At least when the ISS is close to you. Not sure what the window is as far as how far removed it can be from directly overhead, and yet still be able to receive that signal with a small antenna like that. What it takes to hit the repeater I'm less sure. I've heard it can be done with an HT like mine, but I'm guessing that's only possible when it's directly overhead, or very near so. That said, I'd be happy to find out that I'm wrong about that.
- signaturefish 6y ago
  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 6y ago
    Go for it! It really isn't hard, it just requires a small amount of application.
- tmostak 6y ago
  Definitely can pick it up with a HT, just caught it for ~3 minutes in the Bay Area on a Baofeng HT with whip antenna, and even picked up the first part while I was still indoors. There was a lot of static although I could make out some of the sentences.
  - signaturefish 6y ago
    Wow, that's a stronger signal than I thought. Maybe I'll give it a go with a whip the next time the ISS passes over me.
- tomfanning 6y ago
  For listening, a QFH antenna is ideal for LEO objects. It's typically made of copper pipe or the braid of stiff coax.
- jimnotgym 6y ago
  Absolutely you will do well with a dipole.
acqq 6y ago
> 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.
- Shacklz 6y ago
  For those curious when and where to look to see the ISS by eye only: https://james.darpinian.com/satellites/ https://james.darpinian.com/satellites/ The site is incredibly awesome and helped me see the ISS (and other satellites) quite a few times already!
  - Moru 6y ago
    Stellarium is great for this too.
- sgt 6y ago
  I recommend the app ISS Spotter by Martin van Mierloo.
- tomfanning 6y ago
  A 90 degree pass (overhead) is around 10 minutes. And obviously for radio, it doesn't need to be visible (reflecting sunlight), just ~above the horizon.
  - acqq 6y ago
    > A 90 degree pass (overhead) is around 10 minutes. Yes, that's approximately what I remember. The path of ISS is created with the goal that ISS doesn't fly over the same pieces of land or sea. Instead, it takes a lot of orbits before I can see it crossing exactly over my location, giving me around 10 minutes when that cross is ideal, otherwise, it's less, if the current path is close enough at all. Seeing is of course limited more than obtaining a radio signal, as to see ISS it has to fly above you at the time that the sun can reflect from it, and to have clear skies. One doesn't need that to catch just a radio signal, but the ISS path should still be such that it's close to your location, and the time during the FM signal can be received will still be short.
tomfanning 6y ago
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.
- mlyle 6y ago
  > (3) make sure you are listening to the downlink while transmitting (full duplex) to ensure you aren't stepping on other people. If possible. Not everyone has fancy-pants cross-band full duplex capability. I know a couple HTs will do it now, but this is still a bit exotic. This is the strongest space amateur FM repeater ever; surely those of us who are better equipped can use SO-50, etc, without issue, and we shouldn't get too mad if there's a little less-than-ideal operation on something as newbie-friendly as this.
  - dx4100 6y ago
    My cheapest HT can do this. And my 20 year old radio can do it. So not sure about "exotic"
    - jimnotgym 6y ago
      What radios are they?
      - nickysielicki 6y ago
        Kenwood's TH-D72, TH-V71A, and TM-D710G can do it. An incomplete list of full duplex vhf/uhf cross-band FM radios can be found in this reddit comment: https://www.reddit.com/r/amateurradio/comments/97jhik/getting_into_satellites_need_full_duplex_uhfvhf/e48mxpf/?context=3 https://www.reddit.com/r/amateurradio/comments/97jhik/gettin...
        jimnotgym 6y ago

madarco 6y ago

What is the use case of such repeater?

arghwhat 6y ago
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).
- 082349872349872 6y ago
  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 6y ago
    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 microwatt making it from Oregon to Alaska (1650 miles).
- prox 6y ago
  But if the ISS passes over in just a few minutes, is that useable?
  - arghwhat 6y ago
    You have a ~10 minute window every ~90 minutes IIRC. The HAM sport is mostly about establishing contacts of increasing difficulty, not about making boring, rock-solid reliable communication links. 10 minutes is plenty for that, and helps stop people trying to hog the thing as only one person can be received at a time. Outside experimentation (e.g. trying an antenna, transmitter or receiver design), the HAM radios on the ISS are also used for school-astronaut contacts.

PaulHoule 6y ago

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.

sgt 6y ago

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 6y ago
Could be station identification. Many repeaters identify their call with morse code periodically.
- arghwhat 6y ago
  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.)

geocrasher 6y ago

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

sizzzzlerz 6y ago

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?

oliveshell 6y ago
Good question. Some info on tuning for Doppler shift: https://www.qsl.net/ah6rh/am-radio/spacecomm/doppler-and-the-iss.html https://www.qsl.net/ah6rh/am-radio/spacecomm/doppler-and-the...
- sizzzzlerz 6y ago
  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 6y ago
    The open source software gpredict can do this live for you.
tomfanning 6y ago
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.

segfaultbuserr 6y ago

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 6y ago
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.
jbj 6y ago
Apparently there is a non profit that relays some of those messages via satellite: http://forums.othernet.is/t/aprs-outnet-on-outernet/2620 http://forums.othernet.is/t/aprs-outnet-on-outernet/2620

ianpenney 6y ago

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.

dano 6y ago

These radios are built by a retired Qualcomm engineer in La Mesa California https://www.cbs8.com/article/news/local/zevely-zone/la-mesa-man-building-space-radios-from-his-garage/509-445801a4-aaf2-419b-8758-f423d8333a04 https://www.cbs8.com/article/news/local/zevely-zone/la-mesa-...