# Detecting transmission signal destinations

• antistar_

#### antistar_

This is a question for a piece of fiction I am writing.

If a some kind of transmission signal, say radio, microwave, or laser, was transmitted from a planet, could you detect where that signal was being directed to? Say, for example, you picked up a signal coming from another solar system, could you detect that it was being directed specifically at our own? This applies to current or potential near future technology.

Thanks for any help!

If if is directional and you detect it, then it is being directed at you.

What if it was the other way around. Say you picked up a signal being sent into space by the Chinese. Could you figure out where it was going?

If it is directional, you won't pick it up...

What you are asking is like asking what a laser pointer is pointed at if you can't see the dot or the beam.

There is no way to deterimine the shape of the origianal broadcast beam. You will only receive the miniscule protion which is intercepted by your antenna this cannot possibly provide any information about the power of the signal sent in the oppsite direction from earth.

So you are saying that if you intercepted a directional signal coming from Earth and being beamed out into space, that it would be impossible with the technology of today or the future, to determine in which direction it was being beamed?

It would be impossible to detect that the transmitted signal was directional. Sure you could detect the source, that is much different then knowledge of the shape of the original broadcast signal.

Hi, I reckon the problem you really want to solve is how was the directional beam intercepted. This is the difficult part. If it was intercepted by something eg a plane or satellite crossing through the beam through shear fluke then finding direction would be a question of how accurately the detector was keeping track of its own position.

Could a powerful directional beam be detected by scattering from the atmosphere? Also I remember something about radiowaves being bounced over the horison... Can the upper atmosphere reflect radiowaves back? In this case it might be difficult to guess the intended target

Well, let's just assume that it was picked up by a satellite by accident, and that the satellite's exact location was known. Would you then be able to figure out where it was being aimed?

just draw a line that passes through the signal source and the satelite and see where the line aims.

I am not understanding the question.

Are we trying to find the origin of said beam, or are we trying to determine if the original beam is directional. That is, was it beamed directly at the Earth or generally broadcast into a sphere surrounding the source.

What if it was the other way around. Say you picked up a signal being sent into space by the Chinese. Could you figure out where it was going?

Hi Integral, I was referring to this later post, not the original question.

Yeah, sorry. I was a bit vague with my original question.

What B.E.M. is saying is pretty much what I was thinking, but wasn't sure if it was actually scientifically sound.

Thanks for the help so far guys :).