"Aliens Lose in Switch to Digital TV"
Television signals as well as FM radio and radar have served as humans probing into deep space ever since World War II. A lot of people don't believe its possible for extraterrestrials to pick up on television, whether it be analog or digital, because the broadcasts would fade away long before they reached even the nearest star because every doubling of distance causes a four-fold reduction in intensity. But the massive switch to DTV has many others believing signals aliens used to be able to pick up will be replaced with smoother DTV. Radio technology is very sensitive though, and with large antennas it is possible to detect faint radio static from distant corners of the universe. Radio static from analog television is a lot of energy concentrated in a small range of frequencies which create spikes; aliens could find this emission and although they wouldn't have TV picture and sound they would know we were on the air.
However, DTV creates a smooth, low hiss, and television broadcast no longer emits a spike in frequencies that are detectable light-years away. On the other hand, the most powerful signals from our planet are radar transmissions such as the Arecibo telescope, which can be detected with a similarly sized antenna nearly one thousand light-years away. All in all, although its possible aliens will be cut off from being able to detect television broadcasts from earth, other frequencies will still be out there to catch their attention.
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