Radio Telescopes Horn In With GNU Radio

Who doesn’t like to look up at the night sky? But if you are into radio, there’s a whole different way to look using radio telescopes. [John Makous] spoke at the GNU Radio Conference about how he’s worked to make a radio telescope (PDF) that is practical for even younger students to build and operate.

The only real high tech part of this build is the low noise amplifier (LNA) and the project is in reach of a typical teacher who might not be an expert on electronics. It uses things like paint thinner cans and lumber. [John] also built some blocks in GNU Radio that made it easy for other teachers to process the data from a telescope. As he put it, “This is the kind of nerdy stuff I like to do.” We can relate.

The telescope is made to pick up the 21 cm band to detect neutral hydrogen from the Milky Way. It can map the hydrogen in the galaxy and also measure the rotational speed of the galaxy using Doppler shift. Not bad for an upcycled paint thinner can. These are cheap enough, you can even build a fleet of them.

This would be a great project for anyone interested in radio telescopes or space. However, it is particularly set up for classroom use. Students can flex their skills in math, engineering, programming, and — of course — astronomy and physics.

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Tiny Telescope For Simple Radio Astronomy

We are used to imagining radio telescopes as immense pieces of scientific apparatus, such as the Arecibo Observatory in Puerto Rico, or the Lovell telescope in the UK. It’s a surprise then that they can be constructed on a far more modest sale using off-the-shelf components, and it’s a path that [Gonçalo Nespral] has taken with his tiny radio telescope using a satellite dish. It’s on an azimuth-elevation mount using an Ikea lazy susan and a lead screw, and it has a satellite TV LNB at the hot end with a satellite finder as its detector.

So far he’s managed only to image the wall of his apartment, but that clearly shows the presence of the metal supporting structure within it. Taking it outdoors has however not been such a success. If we wanted to hazard a guess as to why this is the case, we’d wish to look at the bandwidth of that satellite finder. It’s designed to spot a signal from a TV broadcast bird over the whole band, and thus will have a bandwidth in the hundreds of MHz and a sensitivity that could at best be described as a bit deaf. We hope he’ll try a different path such as an RTL-SDR in the future, and we look forward to his results.

This isn’t the first simple radio telescope we’ve seen here, aside from at least one other LNB-based one we’ve also shown you a WiFi device.

Desktop Radio Telescope Images The WiFi Universe

It’s been a project filled with fits and starts, and it very nearly ended up as a “Fail of the Week” feature, but we’re happy to report that the [Thought Emporium]’s desktop WiFi radio telescope finally works. And it’s pretty darn cool.

If you’ve been following along with the build like we have, you’ll know that this stems from a previous, much larger radio telescope that [Justin] used to visualize the constellation of geosynchronous digital TV satellites. This time, he set his sights closer to home and built a system to visualize the 2.4-GHz WiFi band. A simple helical antenna rides on the stepper-driven azimuth-elevation scanner. A HackRF SDR and GNU Radio form the receiver, which just captures the received signal strength indicator (RSSI) value for each point as the antenna scans. The data is then massaged into colors representing the intensity of WiFi signals received and laid over an optical image of the scanned area. The first image clearly showed a couple of hotspots, including a previously unknown router. An outdoor scan revealed routers galore, although that took a little more wizardry to pull off.

The videos below recount the whole tale in detail; skip to part three for the payoff if you must, but at the cost of missing some valuable lessons and a few cool tips, like using flattened pieces of Schedule 40 pipe as a construction material. We hope to see more from the project soon, and wonder if this FPV racing drone tracker might offer some helpful hints for expansion.

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Paul Horowitz and the Search for Extra Terrestrial Intelligence

I recently had the opportunity to attend a lecture by Harvard Professor Paul Horowitz. It’s a name you likely recognize. He is best known for his iconic book the Art of Electronics which is often referred to not by its name but by the last names of the authors: “Horowitz and Hill”.

Beyond that, what do you know about Paul Horowitz? Paul is an electrical engineer and physicist and Paul has spent much of his storied career learning and practicing electronics for the purpose of finding intelligent extra terrestrial life.

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See Satellites with a Simple Radio Telescope

Have you got a spare Dish Network antenna lying about? They’re not too hard to come by, either curbside on bulk waste day or perhaps even on Freecycle. If you can lay hands on one, you might want to try this fun radio telescope build.

Now, don’t expect much from [Justin]’s minimalist build. After all, you’ll be starting with a rather small dish and an LNB for the Ku band, so you won’t be doing serious radio astronomy. In fact, the BOM doesn’t include a fancy receiver  – just a hacked satellite finder. The idea is to just get a reading of the relative “brightness” of a radio source without trying to demodulate the signal. To that end, the signal driving the piezo buzzer in the sat finder is fed into an Arduino through a preamp. The Arduino also controls stepper motors for the dish’s azimuth and elevation control, which lets it sweep the sky and build up a map of signal intensity. The result is a clear band of bright spots representing the geosynchronous satellites visible from [Justin]’s location in Brazil.

Modifications are definitely on the docket for [Justin], including better equipment that will allow him to image the galactic center. There may be some pointers for him in our coverage of a tiny SDR-based radio telescope, or from this custom receiver that can listen to Jupiter.

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Listen to the Sun, Saturn, and the Milky Way with Your Own Radio Telescope

Students from the Indian Institute of Science Education and Research combined a commercial satellite dish, a satellite finder and an Arduino, and produced a workable radio telescope. The satellite dish provides the LNB (low noise block) and the associated set-top box is used only for power.  Their LNB employs an aluminum foil shield to block extraneous signals.

In addition to the hardware, the team built Python software to analyze the data and show several practical applications. They used known geostationary satellites to calibrate the signal from the finder (digitized by the Arduino) to determine power per unit voltage. They also calculated the beam width (about 3.4 degrees) and used the sun for other calibration steps.

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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.