Consider pulsars – stellar objects that flash light and radio waves into space with impressive regularity. Pulsars were briefly tagged with the moniker LGM (Little Green Men) upon their discovery in 1967. Of course, these little men didn’t have much to say. Regular pulses don’t convey any information—no more than the ticking of a clock. But the real kicker is something else: inefficiency. Pulsars flash over the entire spectrum. No matter where you tune your radio telescope, the pulsar can be heard. That’s bad design, because if the pulses were intended to convey some sort of message, it would be enormously more efficient (in terms of energy costs) to confine the signal to a very narrow band. Even the most efficient natural radio emitters, interstellar clouds of gas known as masers, are profligate. Their steady signals splash over hundreds of times more radio band than the type of transmissions sought by SETI.[see full article] (http://www.space.com/searchforlife/seti_intelligentdesign_051201.html)

What do you think?

If any intelligence out there would be transmitting a signal with the aim of it being detected by another intelligence, would they confine it to a very narrow band or would they try to cover all frequency bands?

I am inclined to think the latter. This simply because the more bands you cover the greater the chance of your signal being detected, I think. This, of course, has to be weighed in with signal power, but as long as it is detectable, power wouldn't matter.

So what is SETI looking for? An accidental "I Love Lucy" transmission which is the product of an efficiently designed transmitter? It seems not from the article.

Of course, the chances of them finding a detectable transmission at some single, "random" band is much less than them detecting one spread over a broad band of frequencies.

They are searching over the entire radio spectrum. They are looking within it at all specific narrow bands. As noted in your quote the efficiency is the justification for this approach.

It would also be worth quoting this brief concluding extract which neatly disposes of IDs foolish claims in relation to SETI.
In short, the champions of Intelligent Design make two mistakes when they claim that the SETI enterprise is logically similar to their own: First, they assume that we are looking for messages, and judging our discovery on the basis of message content, whether understood or not. In fact, we’re on the lookout for very simple signals. That’s mostly a technical misunderstanding. But their second assumption, derived from the first, that complexity would imply intelligence, is also wrong. We seek artificiality, which is an organized and optimized signal coming from an astronomical environment from which neither it nor anything like it is either expected or observed: Very modest complexity, found out of context. This is clearly nothing like looking at DNA’s chemical makeup and deducing the work of a supernatural biochemist.

They are searching over the entire radio spectrum. They are looking within it at all specific narrow bands. As noted in your quote the efficiency is the justification for this approach.Thanks for the insight. Perhaps I misread then... perhaps.

I gathered that - in the commencing quote - Shostak was referring to the efficiency of a transmitter designed by some extra-intelligence which would transmit over a very wide band of the electromagnetic spectrum as opposed to extreme narrow band transmission.

I wasn't reading it in the conext of the efficiency SETI's efforts to detect the signal, more in the context of efficiency regarding the efforts of the extra-intelligence to produce it.

Maybe Shostak needs to state what he was saying a bit more clearly cause I've reread it and I still get what I got before.