9 ms·

Receiving Starlink Beacons with a HackRF Supercluster

64 points by lightlyused 5y ago

jack_riminton 5y ago
Great! now can anyone explain what that means?
- jsjohnst 5y ago
  This guy chained 8 HackRF SDRs together with a bunch of other radio gear to see the beacons (radio impulses) from Starlink satellites.
exikyut 5y ago
The linked article is fairly light on details and doesn't quite emphasize the interestingness of some of the inline links. https://old.reddit.com/r/RTLSDR/comments/qtofau/starlink_satellites_beacons/ https://old.reddit.com/r/RTLSDR/comments/qtofau/starlink_sat... is particularly interesting and also contains a couple more links (scroll down) Also https://twitter.com/olegkutkov/status/1411124689414541313 https://twitter.com/olegkutkov/status/1411124689414541313 The author's blog https://olegkutkov.me/ https://olegkutkov.me/ definitely looks interesting as well (I don't see an article specifically about the OP topic yet, but there's a lot of other stuff)
dariusj18 5y ago
Things like this remind me how little I understand of electromagnetism and radio signals.
system2 5y ago
It is humbling to look at the pictures and read it carefully then don't even understand what the heck he accomplished by doing the bizarre contraption.
- R0b0t1 5y ago
  He's just receiving the signal. EDIT: My selective reading kicked in, if you check his twitter he's also doing something more modern.
  - tgsovlerkhgsel 5y ago
    The text says the 8 cards are connected to one antenna. To me it sounds like he's doing it because each card only gives him a fraction of the bandwidth he needs to cover. Edit: I don't understand why he needs that much bandwidth though - maybe he just happens to have the cluster, but I suspect he could get basically a 1/8 slice (full height, but only covering 1/8th of the width of the picture) with only one receiver.
    - jsjohnst 5y ago
      You definitely don’t need 160Mhz bandwidth. Based on other articles on the source blog, it’s something he had and the additional bandwidth let’s you track more spectrum at once.
syedkarim 5y ago
I don't believe that the HackRF cluster is required for receiving the beacons. After the 11 GHz signal is down converted by the LNB, an RTLSDR should be fine for reception. happysat77 on Reddit used a PlutoSDR, but an RTLSDR should be ok, since the down converted signal is around 1600 MHz. The bandwidth of the beacon is only 1 kHz or so. https://www.reddit.com/r/RTLSDR/comments/qtofau/comment/hkq24tx/ https://www.reddit.com/r/RTLSDR/comments/qtofau/comment/hkq2...
- petschge 5y ago
  You don't need a cluster of HackRFs to see a single beacon. But the combination of several HackRFs does give you larger instantaneous bandwidth and the ability to track an individual beacon over a wider range of Doppler shifts and hence for a longer time / part part of it's orbit. And the ability to see a whole bunch of beacons at once.
- 8bitsrule 5y ago
  Wow that's some snazzy dish hardware Oleg's using there. I guess he's planning on more than beacon-tracing. 11 GHz is about a 1" wavelength ... dish size?? https://twitter.com/olegkutkov/status/1459552936556732426 https://twitter.com/olegkutkov/status/1459552936556732426 https://twitter.com/olegkutkov/status/1422920308302958600 https://twitter.com/olegkutkov/status/1422920308302958600
nippoo 5y ago
This is really cool! For anyone looking to do a similar project, it's worth noting that HackRFs are pretty low-spec SDRs by current standards: a number of more recent models, such as the XRTX-CS, based on the Lime LMS7002M front-end, achieve far greater tuning bandwidth - you wouldn't have to build a cluster of them, and could get the same throughout for a lower price and complexity!
- kregasaurusrex 5y ago
  Very cool, I didn't know there were better models available than the HackRF & LimeSDR!
- jsjohnst 5y ago
  Do you happen to have a link for the "XRTX-CS". The only seemingly relevant link in Google leads to your HN post :) Edit: Seems you mean XTRX-CS[0]? [0] https://www.crowdsupply.com/fairwaves/xtrx https://www.crowdsupply.com/fairwaves/xtrx
teruakohatu 5y ago
Can the doppler shift be used to build a pseudo GPS? If so, with the number of Starlink satellites, how accurate could this theoretically be?
- JaimeThompson 5y ago
  Check out this link [1] "SpaceX satellite signals used like GPS to pinpoint location on Earth" [1] https://news.osu.edu/spacex-satellite-signals-used-like-gps-to-pinpoint-location-on-earth https://news.osu.edu/spacex-satellite-signals-used-like-gps-...
ncmncm 5y ago
Outrageously off-topic... but I bet if SpaceX put a camera under the satellite, customers would love getting real-time imagery of their house from the exact satellite listening to their Dishy McD. I gather you need a license to collect satellite imagery, which is weird. Or to broadcast it, or something. (But what if it is narrowcast, instead?) SpaceX could totally afford such a license. Speaking of broadcast, the Starlink terminals could be equipped to pick up and cache packets broadcast from a satellite, with a proxy server inside that can deliver cached content. That way, the satellite only needs to send one copy of its Earth View, or the running World Cup, or the new Marvel release, and everybody in the reception cone gets it from the one broadcast, saving bandwidth and system load all around. (Of course, something in the customer's player would need to know to use the proxy server to get video frames. But that is just software, therefore easy. Ish.)
- JaimeThompson 5y ago
  From a geopolitical standpoint that would cause SpaceX an incredible amount of trouble since they have to get government permission in every country they want to operate in. Lots of countries would not easily grant such permission without major strings attached.
  - ncmncm 5y ago
    It would be trivial for SpaceX to serve the images only where they are permitted. People in places where they are not could be shown other places they are allowed to see, instead. (Maybe with a caption inviting them to complain to their Dear Leader.)
    - JaimeThompson 5y ago
      It isn't about the serving, it is about the ability to take images. Countries are really picky about such things but have trouble controlling in a lot of cases because they have no mechanism to stop it. Allowing RF in / out of there areas of control gives them that mechanism.
      - 5y ago
grae_QED 5y ago
I love how whenever I read about radio stuff I feel like I'm reading something from r/VXJunkies.

64 points by lightlyused 5y ago

jack_riminton 5y ago

Great! now can anyone explain what that means?

jsjohnst 5y ago
This guy chained 8 HackRF SDRs together with a bunch of other radio gear to see the beacons (radio impulses) from Starlink satellites.

exikyut 5y ago

The linked article is fairly light on details and doesn't quite emphasize the interestingness of some of the inline links. https://old.reddit.com/r/RTLSDR/comments/qtofau/starlink_satellites_beacons/ https://old.reddit.com/r/RTLSDR/comments/qtofau/starlink_sat... is particularly interesting and also contains a couple more links (scroll down) Also https://twitter.com/olegkutkov/status/1411124689414541313 https://twitter.com/olegkutkov/status/1411124689414541313 The author's blog https://olegkutkov.me/ https://olegkutkov.me/ definitely looks interesting as well (I don't see an article specifically about the OP topic yet, but there's a lot of other stuff)

dariusj18 5y ago

Things like this remind me how little I understand of electromagnetism and radio signals.

system2 5y ago

It is humbling to look at the pictures and read it carefully then don't even understand what the heck he accomplished by doing the bizarre contraption.

R0b0t1 5y ago
He's just receiving the signal. EDIT: My selective reading kicked in, if you check his twitter he's also doing something more modern.
- tgsovlerkhgsel 5y ago
  The text says the 8 cards are connected to one antenna. To me it sounds like he's doing it because each card only gives him a fraction of the bandwidth he needs to cover. Edit: I don't understand why he needs that much bandwidth though - maybe he just happens to have the cluster, but I suspect he could get basically a 1/8 slice (full height, but only covering 1/8th of the width of the picture) with only one receiver.
  - jsjohnst 5y ago
    You definitely don’t need 160Mhz bandwidth. Based on other articles on the source blog, it’s something he had and the additional bandwidth let’s you track more spectrum at once.

syedkarim 5y ago

I don't believe that the HackRF cluster is required for receiving the beacons. After the 11 GHz signal is down converted by the LNB, an RTLSDR should be fine for reception. happysat77 on Reddit used a PlutoSDR, but an RTLSDR should be ok, since the down converted signal is around 1600 MHz. The bandwidth of the beacon is only 1 kHz or so. https://www.reddit.com/r/RTLSDR/comments/qtofau/comment/hkq24tx/ https://www.reddit.com/r/RTLSDR/comments/qtofau/comment/hkq2...

petschge 5y ago
You don't need a cluster of HackRFs to see a single beacon. But the combination of several HackRFs does give you larger instantaneous bandwidth and the ability to track an individual beacon over a wider range of Doppler shifts and hence for a longer time / part part of it's orbit. And the ability to see a whole bunch of beacons at once.
8bitsrule 5y ago
Wow that's some snazzy dish hardware Oleg's using there. I guess he's planning on more than beacon-tracing. 11 GHz is about a 1" wavelength ... dish size?? https://twitter.com/olegkutkov/status/1459552936556732426 https://twitter.com/olegkutkov/status/1459552936556732426 https://twitter.com/olegkutkov/status/1422920308302958600 https://twitter.com/olegkutkov/status/1422920308302958600

nippoo 5y ago

This is really cool! For anyone looking to do a similar project, it's worth noting that HackRFs are pretty low-spec SDRs by current standards: a number of more recent models, such as the XRTX-CS, based on the Lime LMS7002M front-end, achieve far greater tuning bandwidth - you wouldn't have to build a cluster of them, and could get the same throughout for a lower price and complexity!

kregasaurusrex 5y ago
Very cool, I didn't know there were better models available than the HackRF & LimeSDR!
jsjohnst 5y ago
Do you happen to have a link for the "XRTX-CS". The only seemingly relevant link in Google leads to your HN post :) Edit: Seems you mean XTRX-CS[0]? [0] https://www.crowdsupply.com/fairwaves/xtrx https://www.crowdsupply.com/fairwaves/xtrx

teruakohatu 5y ago

Can the doppler shift be used to build a pseudo GPS? If so, with the number of Starlink satellites, how accurate could this theoretically be?

JaimeThompson 5y ago
Check out this link [1] "SpaceX satellite signals used like GPS to pinpoint location on Earth" [1] https://news.osu.edu/spacex-satellite-signals-used-like-gps-to-pinpoint-location-on-earth https://news.osu.edu/spacex-satellite-signals-used-like-gps-...

ncmncm 5y ago

Outrageously off-topic... but I bet if SpaceX put a camera under the satellite, customers would love getting real-time imagery of their house from the exact satellite listening to their Dishy McD. I gather you need a license to collect satellite imagery, which is weird. Or to broadcast it, or something. (But what if it is narrowcast, instead?) SpaceX could totally afford such a license. Speaking of broadcast, the Starlink terminals could be equipped to pick up and cache packets broadcast from a satellite, with a proxy server inside that can deliver cached content. That way, the satellite only needs to send one copy of its Earth View, or the running World Cup, or the new Marvel release, and everybody in the reception cone gets it from the one broadcast, saving bandwidth and system load all around. (Of course, something in the customer's player would need to know to use the proxy server to get video frames. But that is just software, therefore easy. Ish.)

JaimeThompson 5y ago
From a geopolitical standpoint that would cause SpaceX an incredible amount of trouble since they have to get government permission in every country they want to operate in. Lots of countries would not easily grant such permission without major strings attached.
- ncmncm 5y ago
  It would be trivial for SpaceX to serve the images only where they are permitted. People in places where they are not could be shown other places they are allowed to see, instead. (Maybe with a caption inviting them to complain to their Dear Leader.)
  - JaimeThompson 5y ago
    It isn't about the serving, it is about the ability to take images. Countries are really picky about such things but have trouble controlling in a lot of cases because they have no mechanism to stop it. Allowing RF in / out of there areas of control gives them that mechanism.
    - 5y ago

grae_QED 5y ago

I love how whenever I read about radio stuff I feel like I'm reading something from r/VXJunkies.