Designing a Home Radio Telescope for 21 Cm Emission
arxiv.org
arxiv.org
I had it all packed up when moving out to the US (because my imagination told me that houses in the US were far larger than in the UK). The house I ended up buying (despite having a much larger back garden) didn't have the space to set it up again and remain married, so two decades later, it's still in that wooden case... I do, however, have an optical telescope set up (#2)
Back then, we didn't have easy access to SDR's, so there's a feed horn, a down-converter, and I had an external (standalone) WinRadio receiver to actually listen to the feed. That went into an audio card on a linux box, and the waterfall display was beautiful :)
#1: https://imgur.com/a/CDrEeII
#2: https://imgur.com/a/askar-130phq-scope-sb-myt-mount-26mp-cam...
I have an ignorant question ... can home/amateur radio astronomy ever produce layperson-appreciated "imagery"? Something easily understood like optical astronomy can produce? e.g. stitching together a sky scan for a particular emission or something?
With 2 antennas you can start playing around with beam forming. This will enable you to scan the sky from one position without moving the antenna. Then you can map the signal strength to a sky projection.
Have a look at the low-frequency antennas from LOFAR. They look like tents for chickens. A lot of them.
It sounds complex and yes.. it's also a bit complex. But still in the range of a project for the home lab.
Think of a single dish radio telescope as a one-pixel camera, where measuring the emission intensity at each point in the sky lets you build up a map. Typically, this is done with high resolution on the frequency axis, which is used to map Doppler shifts for spectral lines of Hydrogen, for example [1].
With a rooftop antenna, it's not likely to be a very sensitive map, though. You'll see the Sun, and its easy to see the Milky Way transit overhead, but other than that ...
A single dish/node can't really produce photograph-like imagery akin to an optical telescope, more often[1] you get something like in the setileague website hits [2].
[1] Where by "more often" I mean "once in a blue moon".
It's a bit more advanced though, the multiple antennas allows them to "steer" the antenna after the fact through signal processing.
[1]: https://chime-experiment.ca/en
[2]: https://en.wikipedia.org/wiki/Canadian_Hydrogen_Intensity_Ma...
My main goal is to detect the hydrogen line, or maybe some distant/noisy object (can amateurs pick up pulsars?). I also want to understand antennae much better, and maybe make a wire fractal antenna. I have a crazy idea about making a 3D fractal antenna-making bot from Lego or something! :D
(I'm not under any illusions about whether a fractal antenna is "better" but I just like the idea of them)
With multiple synchronized receivers you can build a passive radar.
Single reflections can easily be spotted by just staring at the spectrum (Doppler).
An easy start is always looking at VHF reflection of strong transmitters that are not creating a lot of noise (like FM stations). ILS or VORs stations are classics.
There are also a lot of meteor and space radars ( https://en.wikipedia.org/wiki/GRAVES_(system) ). Universities are super happy in publishing very very detailed (https://www.iap-kborn.de/en/research/department-radar-remote...) specs of their sky radars. And frequencies are well known for ages.
In theory, yes but it's supposed to be pretty tricky. Since it looks like you're up for making antennas, maybe this is for you:
https://britastro.org/wp-content/uploads/2021/03/SmallApertu...
Vela is the "brightest" pulsar but is only visible in the southern hemisphere. B0329+54 is the "brightest" in the northern hemisphere.
Optical astrophotography has stacking software. Radio astronomy has a counterpart in folding software.
The Purcell mentioned is the same one of NMR Nobel and E&M textbook fame.