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.
The paper notes that some designs use the ubiquitous RTL-SDR, but this limits the bandwidth to about 3 MHz. The satellite finder detector is inherently broadband and the team claims a bandwidth for their scope of 1.1 GHz. Some designs (like the Itty Bitty) use a dual LNB to have both. If you are too lazy to build any hardware, you can still get into the radio telescope data crunching game.
If you want an introduction to radio astronomy, you might enjoy Dr. John Morgan’s lecture, in the video below.