The Tiny Radio Telescope

Radio telescopes are one of the more high-profile pieces of scientific apparatus. There is an excitement to stories of radio astronomers of old probing the mysteries of the Universe on winter nights in frigid cabins atop massive parabolas, even if nowadays their somewhat more fortunate successors do the same work from the comfort of their labs using telescopes that may be on the other side of the world.

You might think if you look at the Arecibo Observatory, Lovell Telescope, or other famous pieces of apparatus, that this is Big Science, out of reach for mere mortals such as yourself without billion-dollar research programs. Maybe [Paul Scott] and [Allen Versfeld]’s Tiny Radio Telescope project will change that view.

The NRAO published a radio telescope design a few years ago for use mainly as an educational tool, the Itty Bitty Telescope. It used a satellite TV dish and LNB feeding a signal meter as a simple telescope to detect the Sun, and black body radiation from the surrounding objects. It’s a simple design for kids to get their heads around, and [Scott] and [Allen] have set out to turn it into something more useful with an RTL-SDR instead of a signal meter and a motorised mount for automated observations.

This is one of those projects on Hackaday.io that moves slowly but you know will eventually deliver on its promise. With a 1m dish and a consumer LNB it’s never going to make a discovery that will rock the world, but that’s not the point. It may be science that the astrophysicists moved on from decades ago, but it’s still quite an achievement that the radio sky can be imaged using such mundane equipment.

We’ve featured backyard radio astronomy before a few times, from this UHF school science project to another satellite TV based telescope. Keep them coming!

A thank you to Southgate ARC for the prod.

39 thoughts on “The Tiny Radio Telescope

  1. I’m curious, could a large number of hobbyist telescopes like this be connected over the internet to produce something like a crowd-sourced VLA? I’m sure there are many important and complicated reasons why it wouldn’t work.

      1. At least part of that is possible with GPS, although a High accuracy clock would still be needed.
        And unfortunately you need to be pointing the same direction. I’d wondered about using the horizon to aim (IE have amateurs around the world donating information, and combining information that is in LOS / Over horizon) however attenuation and noise are likely impossible to overcome

        But you could call it the “Community of Ameteur Radioastonomers’ Baseline Incliding Everything” array

      2. >”exquisite timing”

        out of curiosity, about how exquisite is needed?(i dunno because idk about radio astronomy)? it’s possible to get ±10µs of UTC with a gps module attached to a raspi(zero) as an NTP server ( http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html ); converting system clock to TAI or JD seems like it’s pretty doable ( http://docs.astropy.org/en/stable/time/index.html?highlight=tai )

        I am really curious because it’d be pretty neat if it only cost ~$50 to get a time reference good enough for crowdsourced VLA radio astronomy style stuff, assuming such a thing is even possible/useful.

    1. I’ve also wondered if this could be done. You would need very precise timing. Could that be achieved using GPS receivers? It would take a lot of processor power. For this maybe observations could be scheduled in small chunks, recorded and then processed. It doesn’t have to be real time and continuous to be useful right?

    1. Translation… they have graduated upwards from this level of sophistication… though I wouldn’t be surprised if there’s still logging, collating and reanalysing of data from such simple setups for particular purposes.

  2. Wasn’t it a ham who started the field of “radio astronomy”? And much has been written about 18MHz as a place to hear Jupiter.

    There s lots that can be done, it doesn’t have to be at microwave. One probably has to do some reading, these are natural emissions so there won’t be intelligence to help identify something. And I gather some of what’s going on no include radar, an that’s out for most people, no license and power limits too small for the ones with a license.

    Lots of people are amateur astronomers, the fact that many will never find something doesn’t stop them. It’s no different with radio astronomy.

    Michael

    1. Well… kindof. There’s a reason radio astronomy typically operates in microwave: because the atmosphere’s transparent, the galaxy is quiet, and you can make radio receivers that are close to noiseless.

      So with less than $100 in equipment you can pretty much get close to sensitivity levels that’ll get you close to the microwave background levels.

      Jupiter at decameter frequencies is fairly unique, because it’s ridiculously loud – like, hundreds of kJy. With simple ham equipment, you’re pretty much only going to see solar system objects (which are cool in their own right, mind you). Seeing other stuff just requires ridiculously large telescopes and lots of beamforming at those frequencies.

    2. Radio astronomy was discovered “by accident’ by Karl Jansky at Bell Labs around 1930. He was tasked with finding the source of a persistent “hiss” on HF radio circuits, and so build a directional antenna on a carriage. What he discovered was that the “hiss” was coming from the galactic center. He published an article in 1933, and his work was largely ignored by the astrophysics community at the time.

      Then a few years later, a young engineer from Wheaton, Illinois, read Jansky’s article, and decided to build a radio telescope in his back-yard to further investigate. He eventually published a complete map of the sky at 150MHz, and pubished that. THAT act caused “real scientists” to pay attention, and radio astronomy quickly became a first-class branch of observational astronomy.

      When I was much younger, I had an opportunity to work with Grote Reber for the summer, investigating VLF radio astronomy. I declined. I was fool. Ran across his old VLF antennas at a site in Ashton, Ontario a few months back.

    1. > What would it take to gang up many of these to form a massive radio telescope array?

      Completely different equipment. They might incorporate dvb-t dongles, but with just sticking 100 dongles into 100 smart phones and hoping they will cooperate if you just combine their signals in the digital domain, you won’t get any benefit.

      For an array, you need coherent receivers. You can modify some DVB-T dongles to take in an external clock, but you’ll need very good clock distribution to make more than two of these devices somewhat coherent; the price tag on that would pretty much be orders of magnitudes above the cost of a DVB-T dongle, so that if you’re already investing in coherency equipment, you won’t be using terrible 8-bit noisy bandwidth-limited dongles any more. Yes, you can locally link multiple DVB-T devices, but you’ve got to realize that in any receiver array, the gain of adding more receivers reduces with the amount of receivers you already have; and if by adding more receivers you reduce the accuracy of how well these work together whilst not getting any further with your noise, then that’ll pretty soon set a stop to usefulness of building a multi-receiver device.

      There’s actually multiple projects building local and distributed receiver arrays for radioastronomy. To little surprise, once you do the math, the array gain can only still contribute to a growing “virtual” antenna size if the fourth, fifth, … nth receiver you add have a low noise figure. So, no, large arrays of DVB-T sticks will mathematically not happen.

      1. Shouldn’t it be possible to determine time accurately enough through consumer gps units? A stationary receiver may take some time to stabilize the time but isn’t that what folks are already doing here? http://www.lunar-occultations.com/iota/iotandx.htm

        What such an amateur array lacks in detail is certainly made up for in breadth , is it not? Perhaps enough detail to help aim the good ‘scopes on interesting bits of sky.

        1. Time, yes, maybe at least, but for coherency, you’ll mainly need oscillator (read: frequency) equivalence, on a larger time frame. Which means you need a GPS disciplined oscillator that disciplines something like a OCXO (oven-controlled oscillator); these things come in the upper 10² $ price range each.

  3. Just a thought. There are, to my mind, two kinds of TV satellite dishes — the little ones that are fairly modern, and the great whacking mesh ones from forever ago.

    I wonder what the effect would be, of taking one of the horns off a modern such dish, mounting it to a really old big one, and then attaching the Tiny Radio Telescope gear to it…? Would you get better anything, or would it just generally muck it all up?

    1. Some styles of those older ones, the mesh might be a little widely spaced to be a good reflector for the frequencies the new ones use. The C band I think had wavelengths down to 3.5cm, which means something with a finger hole sized mesh would reflect it. Whereas the Ku has wavelengths half that size and smaller, which might go through. There were some solid dishes of that type, but most I see around here are mesh to let the wind and water through a bit. … Also with the difficulty of getting FTA on Ku band any more, the C band have had a bit of a renaissance for what remains on there, so systems are becoming more “highly prized” rather than the “old junk” they were a few years ago. Still might find the odd one “Free if you take it down.” but you gotta beat all the new C band wannabes to it.

  4. I don’t know that you won’t find anything new or exciting with this, I mean we have the Hubble telescope in orbit but amateurs still find something new every now and then with a backyard telescope, more “eyeballs”, even small ones looking means more chances of seeing something interesting.

    1. The probability of an amateur radio telescope discovering anything “new” is significantly smaller than with optical telescopes. Not zero, but not encouragingly greater than zero.

      For optical telescopes, an amateur with a modest budget can purchase/build a substantial instrument. That isn’t generally true for radio telescopes, because the wavelengths differ by several orders of magnitude, which means that “substantial instrument” in the radio domain is a *huge* investment of both time and money.

      1. It is continually amazing what can be discovered by dedicated amateurs looking in areas where the professionals don’t bother. I am reminded that Forest Mims detected mistakes/problems with NASA satellite data with simple home made equipment and consistent record keeping…

        1. That’s what I was thinking, several million dollar instrument you aim it where high probability of payoff, they realistically cover only a narrow strip of sky. So lots of sky left to get lucky in.

        2. It’s not a matter of dedication and patience. It’s a physical matter of dish size. You need a very large dish to resolve smaller details. Very large as in Arecibo. Many folks just getting interested in radio astronomy believe they can achieve optical telescope quality images by scanning the sky and translating the radio power into a visual map. Radio waves coming from outside the solar system are weak and the wavelength of a radio signal compared to visible light is like comparing the height of a matchstick to the height of mount everest.

      2. That’s when you start to think of other ways to increase your effective array size. We do large-scale synchronous cosmic ray detection using GPS synchronized acquisition hardware. Perhaps a network of amateur radioastronomers could do something similar, and could then have a huge effective baseline.

  5. I lived in Collierville, TN for the first half of my life and there was this guy named Paul Wilson http://www.ok1kir.cz/gallery/2300/otherequip//2,3%20GHz%20W4HHK%205.5%20m%20dish.jpg who lived across the street from the High School I attended.

    Course growing up there were more rumors about it’s purpose than anything else. I’d see it every day and look up at his massive obelisk of geek he built in his yard. “Man, whatever that guy is into. He is in it deep”. Was too busy playing in the street in those days skateboarding to really bother finding out why. Now the old guy has passed away and missed a golden opportunity to meet him.

    Legend has it he built it before the Moon landings and would listen to the astronauts.

      1. A big job? Are you kidding? I suppose things could be different in TN but in my city in OH if you had something like that in your yard you would have people dropping in daily, offering to take it down for free just so they can sell the scrap metal. And.. you’d be a fool to let them without negotiating a cut for yourself. That’s a lot of metal!

        Although.. we do have an unusual ‘I think’ number of metal recycling businesses in the city. You see people driving around on trash day (and sometimes not trash day) in rusty old trucks with the beds held together by bungy chords with the rear filled with whatever scrap metal their drivers can find to the point that it billows over like a mushroom or a muffin top. Honestly I am surprised that the street signs and light metal light poles survive in this place.

        Anyway, my guess is that whoever owns the house is also some kind of radio or astronomy amateur and still uses the thing. I’m a little jealous. That’s what I would do. That or it’s still in his family and they keep it up as sort of a memorial to him.

        1. I think our motivation is metered by the seasons. It’s lethal hot in the Summer, can’t do it then. Spring and Fall are short so you’re too busy soaking it in doing as little as possible. Winter, well it ain’t an Ohio winter by any means but cold enough for us we can’t operate in the cold as we’re too busy buying the ingredients for French toast. It’s a real mess man.

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