Hello all!
So I heard a talkshow about the search for extra terrestrial intelligence.
One of the chief scientists, Dr. Seth Shostak mentioned how SETI antenna receivers "listen" to tens of millions of channels simultaneously.
Now, I always thought that you can only listen to one particular frequency at a time, like say in a radio.
For arguments sake, let's say we have a thousand RadioShack radios listening into 1000 different channels. It's doable.
But what makes me wonder is how do they listen to tens of millions of channels simultaneously? They definitely dont have tens of millions of RLC resonance circuits do they?

A) Can some one please explain the technology that lets a computer hear hundreds of millions of channels simultaneously?

B) How does an antenna tap into hundreds of millions of channels simultaneously?

Thanks for your reply in advance.

 

It's a matter of what they call a "channel" and how large a chunk of the spectrum they capture.

Let's take a more mundane example. The AM broadcast band (in the U.S.) is basically 535 kHz to 1605 kHz, for a bandwidth of a little over 1 MHz, which isn't very much. But there are LOTS of channels crammed into that space.

I can use a very simple circuit to simply capture an digitally store the entire band, basically treating it as a 1 MHz wide signal centered around 1 MHz (in rough numbers). I could then go back and analyze the captured data and pull out any particular channel I want. But I can do the same thing in real time using software using a variety of techniques, depending on what I want to focus on -- do I want to select a specific channel and listen to it (demodulate it), for instance, or do I want a visual display showing all of the channels at once and which channels have activity in them? Using a single program, I could write an app that users connect to and each user can select a different channel to listen to, all at the same time.