| Topic: |
Science > Physics |
| User: |
"" |
| Date: |
17 Dec 2004 05:05:14 PM |
| Object: |
Coherent RF radiation (Old Man)? |
Got some quesions regarding RF radiation, which I know
nothing about. I earlier (not to this group) posted some
questions regarding the possibility of RF 'lasers'. At
the time I couldn't see it would be possible to create
an RF laser. The wavelengths of this radiation being so
long that I couldn't envision a 'cavity' large enough
to do this :( I was also told that thermal effects (noise)
would swamp any stimulated emissions at these 'long'
wavelengths.
But now I've been doing some reading on this, and apparently
it is possible, using 'phased arrays'. Supposedly these
use interference effects to direct RF radiation. Neat idea.
How tightly focused can these RF beams be made? I imagine
it's a function of the wavelength... but if EM radiation
really is a particle, one would think it would be possible
to focus things tighter. For example (an extreme example)
would it be possible to focus a 1 Hz wavelength any tighter
than it's wavelength (186,000 miles?)?
Just shows how incomplete our understanding of EM radiation
is, what with all these different models being used to
describe what's going on.
Any links or insights appreciated.
-Eric B
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| User: "Old Man" |
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| Title: Re: Coherent RF radiation (Old Man)? |
17 Dec 2004 09:56:38 PM |
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<boo@fractalfreak.com> wrote in message
news:1103321397.114673.198390@z14g2000cwz.googlegroups.com...
Got some quesions regarding RF radiation, which I know
nothing about. I earlier (not to this group) posted some
questions regarding the possibility of RF 'lasers'. At
the time I couldn't see it would be possible to create
an RF laser. The wavelengths of this radiation being so
long that I couldn't envision a 'cavity' large enough
to do this :( I was also told that thermal effects (noise)
would swamp any stimulated emissions at these 'long'
wavelengths.
But now I've been doing some reading on this, and apparently
it is possible, using 'phased arrays'. Supposedly these
use interference effects to direct RF radiation. Neat idea.
How tightly focused can these RF beams be made? I imagine
it's a function of the wavelength... but if EM radiation
really is a particle, one would think it would be possible
to focus things tighter. For example (an extreme example)
would it be possible to focus a 1 Hz wavelength any tighter
than it's wavelength (186,000 miles?)?
Just shows how incomplete our understanding of EM radiation
is, what with all these different models being used to
describe what's going on.
Any links or insights appreciated.
-Eric B
An ordinary RF dipole antenna, fed by a crystal driven RF
transmitter, emits coherent electromagnetic radiation which
is the primary characteristic of a LASER or MASER.
For an array of dipole antennas of overall dimensions, L x L,
rather than improving upon the divergence angle given by,
delta_theta ~ wavelength / L (radians),
careful phasing is required to meet it. You can't beat it.
[Old Man]
[Old Man]
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