What would SETI pick up from Earth's signals?

[CaptainPanic]

Imagine a SETI program on a planet at 4 light years away (nearest star system from us). What can you pick up from earth?

 

We're broadcasting countless simultaneous things on the same frequencies (how many FM radio channels exist that broadcast on 92.4 FM (39000 hits in google), how many phones are in the same frequency, how many TV stations)? While these signals are located on different places on earth, and don't seem to interfere with each other here (because one source is much stronger than the other), at 4 light years, the different locations on earth are no longer of any significance, and all signals seem to originate from one source (the tiny dot called "Earth").

 

Would it be possible to single out a message, or would it all be signal noise due to the other signals on the same frequencies?

And how strong would the strongest signal be at such distance? Does our magnetosphere also disturb the signals?

 

I realize that some signals are more powerful than others.

 

Lots of questions that all came up when I posted a remark about another newly discovered planet. I was wondering if it's likely that SETI picks up any signal from such a planet even if it would be as advanced as Earth.

[prateek]

Even if signals come frm any intell life we dont know which freq they'll beam us. The signals will be widespaced, the kind lik SETI sends, so they will very very weak adding 2 effect the earth atmosphere and multiple signals at same freq.

[Megabrain]

Seti is rubbish, our deep space network can just about pick up signals from the voyagers, they transmit around 15watts of power at a distance of 10 billion miles, (15 light hours) scale this up and you require some 100million watts of power at the source (and remember this is all narrow beam...)

 

There are no transmitters on earth that trasmit that much power, typical high power uhf transmitters (which radiate all around) with only a small portion of this power going into space radiate a total of around 1 million watts of which about only 5kw (0.005%) can be considered 'beamed' towards a particular point in space. The antennas are designed to radiate around not up.

 

Seti is nothing like as sensitive as the Deep space network. Ask any Radio

Amatuer.

 

Nope, whoever the physycists are that advise SETI they are not radio engineers!