Are SETI researchers looking for the wrong type of signal?
As described in the previous section, SETI researchers look for narrow-band signals, the type that are confined to a small (usually 1 Hz or less) spot on the dial. But if you have a cellular phone, you may be aware that a lot of communications on Earth are now done using a technique known as “spread spectrum.” The broadcast signal is dispersed over a wide range of frequencies. What if ET is also engaged in spread spectrum broadcasting? Would our searches pick up his call? That depends. If the signal is strong enough, it might still be detected with current SETI equipment, although weak broadcasts will be missed. There’s little doubt that in the future, with greatly increased computer capability, our search will encompass these other types of communications. Nonetheless, it’s good to keep in mind that any civilization will realize that narrow-band broadcasts are the most efficient in terms of producing a detectable signal at the receiving end. If they wish to get in touch or, for exampl
