SETI "Wow" signal--modulated or just a beacon?

[toadspittle]

Was the famous SETI “Wow” signal modulated at all (indicating that it might include some encoded info.) or was it simply a steady beacon?

[dylan_73]

From http://www.setileague.org/askdr/decodwow.htm

Let me emphasize that the “Wow!” sequence itself is not a message. What was received appeared to be a CW (unmodulated) signal. The numbers and letters in the much-reproduced computer printout are merely a time-series representation of the signal amplitude, as received at the Big Ear radio telescope.

[scr4]

Found some information here:

…the “Wow!” sequence itself is not a message. What was received appeared to be a CW (unmodulated) signal… From the “Wow!” signal’s temporal correspondence to the antenna pattern, we know that its source was moving with the background stars. From its Doppler shift signature (the local oscillator of the receiver was being chirped at a rate which corresponds to the Earth’s motion with respect to the Galactic center of rest) we can eliminate terrestrial interference, aircraft or spacecraft from consideration.

There’s also a spectrogram (Figure 2 from the above link). So basically it was a narrow bandwidth emission, like an artificial carrier wave or a radar transmitter, with no modulation.

I believe the “antenna pattern” argument means that the antenna was fixed, and the sky was drifting across its “beam” (field of view). As a source drifts into the field the signal becomes stronger, then it fades out again; you can measure the speed of the source by how fast the signal strength changes. “Chirping” means adjusting the frequency continuously.

[toadspittle]

I believe the “antenna pattern” argument means that the antenna was fixed, and the sky was drifting across its “beam” (field of view).

Yep. That part was explained rather well in space.com’s story today … just wasn’t clear on the nature of the signal itself. Thanks, both of you.

a radar transmitter

an excellent illustration–thanks.

Second question–I know that the signal was ridiculously powerful (30 times standard deviation, I believe they said…), but how much juice would have to be pumped into it to create such a transmission? (obviously would depend on distance, but since they’ve only pinned it down to “the direction of Sagittarius”, that would be tougher to detrmine) In short, for any reasonably distant star, would it be equivalent to the intentional Arecibo broadcast (presumably a high-powered signal intended to reach a cluster tens of thousands of light years away), or just ordinary leakage from other sources (ground-based radar, planetary telecom carrier waves, etc.)?