Your Own 11.2 GHz Radio Telescope

Modern life has its conveniences. Often, those conveniences lead to easier hacks. A great example of that is the rise of satellite television and the impact it has had on amateur radio telescopes. There was a time when building a dish and a suitable low noise amplifier was a big deal. Now they are commodity parts you can get anywhere.

The antenna in use is a 1.2-meter prime focus dish. Some TV dishes use an offset feed, but that makes it harder to aim for use in a radio telescope. In addition to off-the-shelf antenna and RF components, an AirSpy software-defined radio picks up the frequency-shifted output from the antenna. There is more about the software side of the build in a follow-up post. We liked that this was a pretty meaty example of using GNU Radio.

A little math predicts that the telescope will see about 1.45 degrees of sky in the half-power bandwidth. Since coax is very lossy at 11.2 GHz, a converter sits right at the feed point and shifts the incoming signal down to about 1.4 GHz. The signal then goes through a bandpass filter, an amplifier, and on to the AirSpy.

As radio telescopes go, 1.2 meters isn’t huge, though you can easily see the sun and the moon transit. The post says you should be able to hear the Milky Way, but that other stellar radio sources may be too faint for the modest equipment.

We see a lot more radio telescope projects these days. Even a relatively small set up can do some things.