RE: Low-elevation skymapping at 2.45 Ghz
Do optical mirrors still work in the microwave regime? I have no idea. -TD
From: "Major Variola (ret)" <mv@cdc.gov> To: "cypherpunks@al-qaeda.net" <cypherpunks@al-qaeda.net> Subject: Low-elevation skymapping at 2.45 Ghz Date: Tue, 15 Jun 2004 15:09:26 -0700
Telescopes are sold for < $200 which include programmable positioning devices (2 axes obvioiusly). I suppose its just a reduction drive and the usual electro-mech-control stuff but it implies a high degree of angular resolution for cheap. Has anyone:
1. ever used the refractor type telescope tube as-is as a super-long pringles directional 802.11 antenna? In fact the front optics may not interfere...
2. ever used the electronically controlled mount on a steady platform and a highly directional antenna (dishes included) to really see what the world really looks like at 2.mumble Ghz passive with an 802.11 decoder? I mean, radio astronomers do detailed sky surveys all the time. Why restrict yourself to the sky?
(Yes, I realize our friends at Ft Meade have probably been using scanning-tunnelling-microscope type piezo-servo actuators to keep a steady gaze for some time..)
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On Wed, Jun 16, 2004 at 10:50:34AM -0400, Tyler Durden wrote:
Do optical mirrors still work in the microwave regime? I have no idea.
Aperture is tiny (and expensive, exponentially so). Visible wavelength vs. microwave is a complete overkill in terms of mirror precision (lambda/10..100). Depending on angular resolution you might want to check out a small parabolic sat dish (less wind load on the mount -- which better be not azimuthal -- use a stepper-driven equatorial platform). If you're just going to scan the horizont, it's just one degree of freedom. 2 1/2 if you wiggle a little up and down. Easy enough to improvise for cheap, especially if you do it with a monster dish, which isn't at all like a truss of a lightweight giant scope. -- Eugen* Leitl <a href="http://leitl.org">leitl</a> ______________________________________________________________ ICBM: 48.07078, 11.61144 http://www.leitl.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE http://moleculardevices.org http://nanomachines.net [demime 1.01d removed an attachment of type application/pgp-signature]
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