"A detector that is only sensitive to this spectral region has the capability to operate in the daylight, even while pointing at the sun, and pick up little background radiation"
How much are UV receivers (note, not the same thing as a mere UV detector)? Gotta be kinda expensive, I would think (ie, in the 4-digit range), but I could be wrong. And preferably, it would be nice if it could run up to 11Meg/sec or so.
Seems to me if one wanted broadcast, operating in the 1550-nm range and then using good old EDFAs might work, if one had the right kind of omnidirectional IR 'antenna' (or whatever such a thing would be called). Then of course, the broadcast cost would be kind of expensive (say $5000), but the detectors could be cheap ($100 or less). The only drawback here is fog (1550nm doesn't go too good through fog, but rain and snow are apparently fine).
-TD
From: Steve Schear <[EMAIL PROTECTED]>
To: Thomas Shaddack <[EMAIL PROTECTED]>, cypherpunks <[EMAIL PROTECTED]>
Subject: Re: Idea: Sidestepping low-power broadcast regulations with infrared
Date: Mon, 17 Mar 2003 08:40:05 -0800
At 03:13 PM 3/17/2003 +0100, Thomas Shaddack wrote:Using a powerful high-frequency modulated infrared source (eg, a bank of LEDs) located on a highly visible place, it couldbe possible to facilitate local community broadcasts, effectively sidestepping all FCC regulations.
Better to ignore low power regs and challenge the FCC to demonstrate for each and every such station that their signal measurably interferes at receivers in another state with another station. Interference at receivers within the same state as the low power transmitters is not a valid constitutional basis for FCC regulation.
Regarding LED broadcasts, you should consider RF modulated mid-UV lamps. There is a wide swath of spectrum from 230 to 280 nanometers
created by the ozone layer. Little sun light in this frequency range, the only significant natural illumination source, reaches most parts of the earth. A detector that is only sensitive to this spectral region has the capability to operate in the daylight, even while pointing at the sun, and pick up little background radiation. A detector operating in this wavelength region need not be directional and will have an increased performance by orders of magnitude because of the reduction of the background noise. Furthermore, precise alignment of the transmitter and receiver is dispensed with since a detector does not have to operate in the line-of-sight but can function in a wide field-of-view mode to sense radiation scattered by the modulated UV signal.
Multi-watt transmitters can be constructed from inexpensive, commercially available, Ar-Hg discharge lamps. Data rates can easily exceed 100s kbps (megabit data rates have been reported). By selection of different Hg isotopes in the lamps multiple channel operation is possible. Reception using inexpensive, solid-state, sensors is assumed.
See U.S. Patent 4,493,114.
steve
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