Perhaps I'm missing something, but it seems to me that if I were an alien civilization and wanted to send out a beacon, in as wide an angle as possible, across the vast reaches of space and overcome as much of the path losses as possible using the least energy I certainly wouldn't use a narrow band signal. Quite the contrary, I'd want to spread a low bandwidth information signal across the widest practical spectrum. Its much easier to increase process gain (the ratio of the baseband information signal to the final carrier bandwidth) than transmit power. While a narrow band signal from Arecibo's powerful transmitter/antenna combination can be detected at a distance of about 300 light years. It subtends a very small angle greatly reducing the likelyhood of contact. Switching to a spread spectrum approach could allow broadening the antenna pattern, and thereby its chances of detection, significantly without reducing its effective range. Notice how 63 dB (or over 2,000,000 fold effective increase in transmit power) of process gain enables handheld GPS receivers to pull in signals from satellites, sent using only a few watts of transmit power, without much of an antenna. If all this seems to make sense, then why are the SETI people apparently seaching the skies with lots of narrow band receivers? They don't seem to be employing any broadband correlator techniques, so spread signals will probably be missed. --Steve