Aside from the wok, which serves as the main reflector, you’ll need a bit of coaxial cable and some stiff copper wire to fashion a small dipole antenna ... 1420-MHz hydrogen line signal, which ...

That’s the electromagnetic spectral line of hydrogen ... a reasonable 21-cm rig can be had for about $200 or so, less the antenna. He promises a follow-up paper on homebrew 21-cm antennas ...

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 ... the hydrogen emission line is sometimes called the 21 ...

A 19.8 kW PV system is powering a telecommunications antenna at a French air control center. When it produces more energy than needed, the surplus is used to produce hydrogen which is then ...