According to a University of Massachusetts - Amherst press release:

"A radio telescope works just like your car radio," UMass Amherst astronomer Peter Schloerb explains. "There is an antenna to pick up the signals and when we tune over the frequency band we come across a nice strong signal at some points. These signals arise from the tumbling of molecules in giant clouds of gas and dust in the source galaxy. The main difference from a car radio, of course, is that our antenna is really, really big and our receiver is not only very sensitive but it also looks at all the frequencies at the same time. Finally, we record our signals in the computer rather than playing them on a speaker."

The Large Millimeter Telescope website offers more detail about the project.

Henry Romero / Reuters

The world's largest milimetric telescope (50 metres in diameter) is seen in the Sierra Negra Volcano, at an altitude of 15,000 ft., which lies between the states of Puebla and Veracruz June 20. The telescope, optimized for astronomical observations at millimeter wavelengths, is the result of a bi-national project between Mexico and the U.S., according to its website. The first observations were made at 3 mm on June 1, reported by Instituto Nacional de Astrofisica, Optica y Electronica (INAOE).

Henry Romero / Reuters

The world's largest milimetric telescope (50 metres in diameter) is seen in the Sierra Negra Volcano, at an altitude of 15,000 ft., which lies between the states of Puebla and Veracruz June 20. The telescope, optimized for astronomical observations at millimeter wavelengths, is the result of a bi-national project between Mexico and the U.S., according to its website. The first observations were made at 3 mm on June 1, reported by Instituto Nacional de Astrofisica, Optica y Electronica (INAOE).

Henry Romero / Reuters

INAOE's Director Alberto Carraminana speaks during an interview to Reuters television at the world's largest milimetric telescope (50 metres in diameter) at the Sierra Negra Volcano.