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  #1  
Old November 4th 04, 07:58 PM
Ed
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Default Radio Transmissions

Can someone refresh my memory on wave interference? I've been out of
school too long to remember any details.

As I recall, at least all similar waves interfer with each other to some
degree. How similar in frequency and type do those waves have to be to
cause some interference? How does that afect what you would be able to
detect at one light year? Would those signals retain enough of their
original form to be easly detected?

We do know that we are still able to pick out the signals from our most
distant still working probes because of receiver improvements. However
that is a weak transmission, and it is the only signal in that area.

--
Ed

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  #2  
Old November 19th 04, 04:12 PM
Alfred A. Aburto Jr.
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Ed wrote:
Can someone refresh my memory on wave interference? I've been out of
school too long to remember any details.

As I recall, at least all similar waves interfer with each other to some
degree. How similar in frequency and type do those waves have to be to
cause some interference?


I think your first sentence pretty much sums it up ...

Technically I guess it would depend on items such as signal to noise
ratios, signal coherence, and correlation coefficients, but there is no
need to get in to all that ...

How does that afect what you would be able to
detect at one light year? Would those signals retain enough of their
original form to be easly detected?


The more frequencies you have the more information you can store of course.

On the other hand given an equal amount of power a signal at one
frequency will be detectable to much greater range than a signal
with the same power spread out over a bunch of frequencies ...

Some trade offs (assumptions) have to be made ...


We do know that we are still able to pick out the signals from our most
distant still working probes because of receiver improvements. However
that is a weak transmission, and it is the only signal in that area.


Yes, and since one knows what the signal is exactly (the transmitted
waveform) then one can tune the reciever to optimize the detection of
that signal alone ("matched filters" for example) .... a signal with
unknown properties is much more difficult to detect ... of course if it
has alot of power then regardless of other things, one will detect it
probably (one has to look too --- if one doesn't look then it won't be
detected of course) ...
Al
 




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