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CHART: Completely Hackable Amateur Radio Telescope

207 points by cenazoic 3y ago

JKCalhoun 3y ago
I find myself increasingly drawn to SDR. I only played with it a bit (got a cheap RTL-SDR and played around with some "waterfall" software). I wish the software was in fact a little slicker. For my brief toying with it, the apps felt like either Swiss Army knife apps with too many knobs, and/or had kind of janky UI. Radio astronomy seems like another cool use of SDR that could draw me back in to learn more about it.
jejeyyy77 3y ago
are there any example images showing what can be captured?
- owlmirror 3y ago
  You can find a picture of what the data you capture looks like in the "Taking Data" page in the tutorials. Unfortunately the "Analysis" page is "under construction". But you won't get photographs, like you would get from an optical telescope.
  - empyrrhicist 3y ago
    At least in principal it is indeed possible to process data from a collection of radio telescopes into images, and they often overlay the data on optical images to see regions of radio emission. Whether that's in the reach of amateur equipment is another story that I don't have insight into. It would certainly be cool if it were possible. Check out the Galaxies tab here: https://public.nrao.edu/gallery/ https://public.nrao.edu/gallery/
    - lawlessone 3y ago
      Do they work during the day or does the scattering and sunlight also make that impossible?
      - empyrrhicist 3y ago
        I'm not the right person to ask. I'm guessing the EM environment is too noisy, but who knows.
      - tomr_stargazer 3y ago
        Yes! Radio astronomy at most frequencies is totally feasible 24 hours a day, as long as you’re not pointing too close to the Sun. Source: I’m a radio astronomer.
  - jejeyyy77 3y ago
    ahh duh that makes sense.
- svijaykr1 3y ago
  I found a paper that was submitted recently to arxiv that has some more detail : https://arxiv.org/pdf/2307.11173.pdf https://arxiv.org/pdf/2307.11173.pdf
lawlessone 3y ago
I really like this , i have an orginal Pi and one of those cheap usb SDR's sitting around doing nothing.
thoop 3y ago
This is really cool. Could you build a few of these and make an interferometer? I remember reading that interferometers are usually all connected by physical cables with physical loops to make sure the incoming data is combined at exactly the right time. But are we at a point now where that can somehow be done intelligently in software? Or are these little RTL-SDR's not accurate enough to even begin trying that?
- ooterness 3y ago
  Broadly speaking, the main prerequisite to interferometry is to make sure all the RF circuits are phase-coherent, meaning that all the oscillators are operating in lockstep within some tolerance. The accuracy needs to be within about 1/10th of a period, give or take. I'm not sure the min/max frequency range for this system, but I saw 1.4 GHz in a screenshot, which would yield a tolerance of about 0.1 * (1 / 1.4 GHz) = 70 picoseconds. That is achievable with the right hardware, but unfortunately the RTL-SDR doesn't include an option to use an external clock reference. As a result, each dongle's ADC sample timing and RF synthesizer phase will constantly be wandering relative to the others. It's not a one-time calibration; it's an ongoing random walk that changes on a millisecond-by-millisecond basis. In theory you might be able to pull it off if you had a separate emitter in view of each antenna, calibrate each unit based on that signal, and then synchronize everything in software. But at some point it's easier to just use hardware that has an external clock input, and avoid the whole problem.
  - toomuchtodo 3y ago
    Can you use GPS as clock reference? https://www.gps.gov/applications/timing/ https://www.gps.gov/applications/timing/ https://ilrs.gsfc.nasa.gov/docs/timing/gpsrole.pdf https://ilrs.gsfc.nasa.gov/docs/timing/gpsrole.pdf
    - civilitty 3y ago
      Theoretically yes but using GPS time of flight to synchronize sensor triggers to within tens of picoseconds is so far outside of "amateur" that you might as well incorporate and start replying to DoD RFPs. When your math starts requiring relativistic physics, it's a lot easier and cheaper to just run some fiber.
deleted 3y ago
[deleted]
ale42 3y ago
My first understanding of the title: a telescope for amateur radio... I was wondering what it was supposed to be exactly ;-)
- vvoid 3y ago
  A stacked Yagi array. Seriously!
fukpaywalls2 3y ago
The youtube is about 4 years old. There does not seem to be much updates. Sounds like fun project overall.
snats 3y ago
What can you do with the data that you get? It seems like a really cool project but I feel that it has been a long time since they posted something and the analysis sections seems incomplete. I want to do one of this, but I want to know what is the data that I get and what cool stuff you can do.
- cchance 3y ago
  this exactly was super interested and then clicked and the page that shows what to actually do after getting data collected being blank feels like... ya this is a dead project where they couldnt explain wtf to do with it lol maybe not but thats how it came off
  - snats 3y ago
    I ended up going into a bit of a rabbit hole. I learned that there is this telescope you can use[1] and there is a small guide[2] in there to check out how to use it. It is a bit more information from that. [1] https://www.pictortelescope.com/observe https://www.pictortelescope.com/observe [2] https://www.pictortelescope.com/Observing_the_radio_sky_with_PICTOR.pdf https://www.pictortelescope.com/Observing_the_radio_sky_with...
peter_d_sherman 3y ago
Amazing what one can build out of Aluminum Foil...
dekhn 3y ago
Could you mount this on an alt-az platform and get radio image data? I'm not super interested in manual pointing and just looking at spectra.
bmitc 3y ago
Does anyone have any suggestions for what to do with amateur radio astronomy? I recently looked into this a bit and came to the conclusion that to do anything actually interesting would require rather substantial investment in a big dish and having a place in the middle of nowhere away from interference. I had a hard time getting a list of interesting things you could do with more modest investments. Looking into Radio Jove and the Itty Bitty Telescope seemed like they would just be educational projects that wouldn't yield fruitful, long-term projects. Most projects seemed like just listening/watching to the Sun and Jupiter for various emission pulses, which seems like it would get boring pretty quickly after the initial learning exercise. Although the more interesting of the two, radio astronomy, for the amateur, seemed like it wouldn't yield as interesting results as visible light astronomy.
- superkuh 3y ago
  1. Small apertures' one advantage is their being able to see a large amount of the sky at once. For any coherent aperture the larger it's span in a direction the smaller the beam pattern is in the perpendicular direction upon the sky. The bigger your collector the smaller your beamwidth the less you can see at once. Big dishes have small FOV and aren't good for monitoring the entire sky. There are ways of getting around this: physically scanning the big antenna, multi-apertures for receive across the focal plane, or by abandoning actual imaging and measuring the correlations between arrays of lower gain (smaller) apertures. But the best way (if the signal is loud enough) is just to have a smaller aperture. Real science monitoring for transient radio signals can and is being done with literally just using the feedhorn from a large dish by itself (with some precise clocks, expensive lna, receiver, and time stamping) to detect FRB (and other high power transients), https://arxiv.org/abs/2001.05077 https://arxiv.org/abs/2001.05077 STARE2: Detecting Fast Radio Bursts in the Milky Way Multiple stare2 type instruments distributed around the world are likely to do real radio astronomy in the near'ish future. This is amateur scale possible. In the "Completely Hackable Amateur Radio Telescope" they're using a pyramidal dish because it's easier to construct but for trying to contribute to "real" radio astronomy you'd want a choke ring feed horn or at the very least a conical horn. The idea is to minimize sidelobes which otherwise prevent you from knowing for sure the signal you received came from the direction the horn is pointing. 2. Another low hanging amateur accessible "real science" is actually doing something when you're receiving solar radio emissions. Calculate the velocity of a CME shock by the frequency drift as it travels upwards through decreasing magnetic field. Or even more audacious, use a hackrf (or ettus usrp b200 or something) to frequency hop at 8 GH/s over a few hundred MHz bandwidth and record the fine structure present at milli and microsecond timescales precent in many types of solar radio bursts. Things like spectrogram zebra patterns and fiber bursts and other unexplained highly coherent fine timescale patterns which still lack accepted physical explaination today. Particularly in that their very short timescales indicate the emission regions have to be only ~a handful of kilometers in scale but outshine the rest of the sun. Whatever "small" solar features are making these short intense radio emissions are open to even amateur interpretation at this point.
bheadmaster 3y ago
Good thing it is completely hackable. A slightly hackable amateur radio telescope would make a pretty shitty acronym.
nyankosensei 3y ago
The Society for Amateur Radio Astronomy lists some other interesting projects for beginners: https://radio-astronomy.org/getting-started https://radio-astronomy.org/getting-started
pfdietz 3y ago
If Grote Reber could do it in 1937, so can you!

207 points by cenazoic 3y ago

I find myself increasingly drawn to SDR. I only played with it a bit (got a cheap RTL-SDR and played around with some "waterfall" software). I wish the software was in fact a little slicker. For my brief toying with it, the apps felt like either Swiss Army knife apps with too many knobs, and/or had kind of janky UI. Radio astronomy seems like another cool use of SDR that could draw me back in to learn more about it.

jejeyyy77 3y ago

are there any example images showing what can be captured?

owlmirror 3y ago
You can find a picture of what the data you capture looks like in the "Taking Data" page in the tutorials. Unfortunately the "Analysis" page is "under construction". But you won't get photographs, like you would get from an optical telescope.
- empyrrhicist 3y ago
  At least in principal it is indeed possible to process data from a collection of radio telescopes into images, and they often overlay the data on optical images to see regions of radio emission. Whether that's in the reach of amateur equipment is another story that I don't have insight into. It would certainly be cool if it were possible. Check out the Galaxies tab here: https://public.nrao.edu/gallery/ https://public.nrao.edu/gallery/
  - lawlessone 3y ago
    Do they work during the day or does the scattering and sunlight also make that impossible?
    - empyrrhicist 3y ago
      I'm not the right person to ask. I'm guessing the EM environment is too noisy, but who knows.
    - tomr_stargazer 3y ago
      Yes! Radio astronomy at most frequencies is totally feasible 24 hours a day, as long as you’re not pointing too close to the Sun. Source: I’m a radio astronomer.
- jejeyyy77 3y ago
  ahh duh that makes sense.
svijaykr1 3y ago
I found a paper that was submitted recently to arxiv that has some more detail : https://arxiv.org/pdf/2307.11173.pdf https://arxiv.org/pdf/2307.11173.pdf

lawlessone 3y ago

I really like this , i have an orginal Pi and one of those cheap usb SDR's sitting around doing nothing.

thoop 3y ago

This is really cool. Could you build a few of these and make an interferometer? I remember reading that interferometers are usually all connected by physical cables with physical loops to make sure the incoming data is combined at exactly the right time. But are we at a point now where that can somehow be done intelligently in software? Or are these little RTL-SDR's not accurate enough to even begin trying that?

ooterness 3y ago
Broadly speaking, the main prerequisite to interferometry is to make sure all the RF circuits are phase-coherent, meaning that all the oscillators are operating in lockstep within some tolerance. The accuracy needs to be within about 1/10th of a period, give or take. I'm not sure the min/max frequency range for this system, but I saw 1.4 GHz in a screenshot, which would yield a tolerance of about 0.1 * (1 / 1.4 GHz) = 70 picoseconds. That is achievable with the right hardware, but unfortunately the RTL-SDR doesn't include an option to use an external clock reference. As a result, each dongle's ADC sample timing and RF synthesizer phase will constantly be wandering relative to the others. It's not a one-time calibration; it's an ongoing random walk that changes on a millisecond-by-millisecond basis. In theory you might be able to pull it off if you had a separate emitter in view of each antenna, calibrate each unit based on that signal, and then synchronize everything in software. But at some point it's easier to just use hardware that has an external clock input, and avoid the whole problem.
- toomuchtodo 3y ago
  Can you use GPS as clock reference? https://www.gps.gov/applications/timing/ https://www.gps.gov/applications/timing/ https://ilrs.gsfc.nasa.gov/docs/timing/gpsrole.pdf https://ilrs.gsfc.nasa.gov/docs/timing/gpsrole.pdf
  - civilitty 3y ago
    Theoretically yes but using GPS time of flight to synchronize sensor triggers to within tens of picoseconds is so far outside of "amateur" that you might as well incorporate and start replying to DoD RFPs. When your math starts requiring relativistic physics, it's a lot easier and cheaper to just run some fiber.

deleted 3y ago

[deleted]

ale42 3y ago

My first understanding of the title: a telescope for amateur radio... I was wondering what it was supposed to be exactly ;-)

vvoid 3y ago
A stacked Yagi array. Seriously!

fukpaywalls2 3y ago

The youtube is about 4 years old. There does not seem to be much updates. Sounds like fun project overall.

snats 3y ago

What can you do with the data that you get? It seems like a really cool project but I feel that it has been a long time since they posted something and the analysis sections seems incomplete. I want to do one of this, but I want to know what is the data that I get and what cool stuff you can do.

cchance 3y ago
this exactly was super interested and then clicked and the page that shows what to actually do after getting data collected being blank feels like... ya this is a dead project where they couldnt explain wtf to do with it lol maybe not but thats how it came off
- snats 3y ago
  I ended up going into a bit of a rabbit hole. I learned that there is this telescope you can use[1] and there is a small guide[2] in there to check out how to use it. It is a bit more information from that. [1] https://www.pictortelescope.com/observe https://www.pictortelescope.com/observe [2] https://www.pictortelescope.com/Observing_the_radio_sky_with_PICTOR.pdf https://www.pictortelescope.com/Observing_the_radio_sky_with...

peter_d_sherman 3y ago

Amazing what one can build out of Aluminum Foil...

dekhn 3y ago

Could you mount this on an alt-az platform and get radio image data? I'm not super interested in manual pointing and just looking at spectra.

bmitc 3y ago

Does anyone have any suggestions for what to do with amateur radio astronomy? I recently looked into this a bit and came to the conclusion that to do anything actually interesting would require rather substantial investment in a big dish and having a place in the middle of nowhere away from interference. I had a hard time getting a list of interesting things you could do with more modest investments. Looking into Radio Jove and the Itty Bitty Telescope seemed like they would just be educational projects that wouldn't yield fruitful, long-term projects. Most projects seemed like just listening/watching to the Sun and Jupiter for various emission pulses, which seems like it would get boring pretty quickly after the initial learning exercise. Although the more interesting of the two, radio astronomy, for the amateur, seemed like it wouldn't yield as interesting results as visible light astronomy.

superkuh 3y ago
1. Small apertures' one advantage is their being able to see a large amount of the sky at once. For any coherent aperture the larger it's span in a direction the smaller the beam pattern is in the perpendicular direction upon the sky. The bigger your collector the smaller your beamwidth the less you can see at once. Big dishes have small FOV and aren't good for monitoring the entire sky. There are ways of getting around this: physically scanning the big antenna, multi-apertures for receive across the focal plane, or by abandoning actual imaging and measuring the correlations between arrays of lower gain (smaller) apertures. But the best way (if the signal is loud enough) is just to have a smaller aperture. Real science monitoring for transient radio signals can and is being done with literally just using the feedhorn from a large dish by itself (with some precise clocks, expensive lna, receiver, and time stamping) to detect FRB (and other high power transients), https://arxiv.org/abs/2001.05077 https://arxiv.org/abs/2001.05077 STARE2: Detecting Fast Radio Bursts in the Milky Way Multiple stare2 type instruments distributed around the world are likely to do real radio astronomy in the near'ish future. This is amateur scale possible. In the "Completely Hackable Amateur Radio Telescope" they're using a pyramidal dish because it's easier to construct but for trying to contribute to "real" radio astronomy you'd want a choke ring feed horn or at the very least a conical horn. The idea is to minimize sidelobes which otherwise prevent you from knowing for sure the signal you received came from the direction the horn is pointing. 2. Another low hanging amateur accessible "real science" is actually doing something when you're receiving solar radio emissions. Calculate the velocity of a CME shock by the frequency drift as it travels upwards through decreasing magnetic field. Or even more audacious, use a hackrf (or ettus usrp b200 or something) to frequency hop at 8 GH/s over a few hundred MHz bandwidth and record the fine structure present at milli and microsecond timescales precent in many types of solar radio bursts. Things like spectrogram zebra patterns and fiber bursts and other unexplained highly coherent fine timescale patterns which still lack accepted physical explaination today. Particularly in that their very short timescales indicate the emission regions have to be only ~a handful of kilometers in scale but outshine the rest of the sun. Whatever "small" solar features are making these short intense radio emissions are open to even amateur interpretation at this point.

bheadmaster 3y ago

Good thing it is completely hackable. A slightly hackable amateur radio telescope would make a pretty shitty acronym.

nyankosensei 3y ago

The Society for Amateur Radio Astronomy lists some other interesting projects for beginners: https://radio-astronomy.org/getting-started https://radio-astronomy.org/getting-started

pfdietz 3y ago

If Grote Reber could do it in 1937, so can you!