How to build a home radio telescope to detect clouds of hydrogen in the Milky Way

If I ask you to picture a radio telescope, you probably imagine a large dish pointing to the sky, or even an array of dish antennas such as the Very Large Array. What you likely don't imagine is something that resembles a TV dish in your neighbor's backyard. With modern electronics, it is relatively easy to build your own radio telescope. To understand how it can be done, check out a recent paper by Jack Phelps posted to the arXiv preprint server.