Jacques Richer Email to Info@

-- Forwarded message --
From: jricher <moc.rehcirj|rehcirj#moc.rehcirj|rehcirj>
Date: Sat, Jan 19, 2008 at 7:59 PM
Subject: Moving data out to kiosks
To: gro.egdirbycaretil|ofni#gro.egdirbycaretil|ofni

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Here's a blue sky idea for you:
In the 1960's and 1970's, various governments worked with and perfected
a technique called NVIS (Near Vertical Incidence Skywave/Scattering) for
creating reliable shortwave radio networks out to about 500 miles. If
you used shortwave transmitters pushing out something simple and cheap
to decode like AM with one sideband suppressed, and overlaid that with a
simple, robust digital signaling protocol, you could hit effectively all
your kiosks in one night.

The basic idea is this:

~ TRANSMIT SIDE
digital content -> digital encoder (software) -> compact disk audio ->
shortwave transmitter -> NVIS antenna

~ RECEIVE SIDE

beverage antenna -> simple (crystal controlled) receiver -> baseband DSP
- -> microcontroller -> SD card

The nice part about this is that all the RF technology is basically
1970s - so you don't have any funky surprises. The transmitter(s) can be
run someplace where power and technical services are fairly simple and
straightforward.

On the receive side, your DSP can be pretty braindead, since we're only
using a sample rate of 44 or 48khz. If you use something simple and
stupid like QAM with some kind of basic forward error correction, the
receiver can be a lot less technically sophisticated than the
transmitter. The receive antenna can be as simple as 50' of magnet wire
stapled to a fence - making it simple to set up, cheap, and easy to
maintain. I think you could set this up to be pretty highly automated —
stick the SD card in and turn the machine on at sundown, and pick up
your data in the morning. From a size perspective, I'm thinking a fat
cigarette pack with a few LEDs on it, but it's just an idea

~ Jacques Richer (N1ZZH)

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