smith@wookie.dec.com (Willie Smith) (01/14/91)
Several people in the last few weeks have expressed an interest in remote
data communications with their mobile platforms. I've personally run
across the following options:
1) O'Neil Communications LAWN
This is a spread-spectrum 9600-baud full duplex box that runs in the 900
MHz ham band (allowed by a recent FCC rule change). I called them when the
box first came out and found that it had to run with a PeeCee, but they
were working on (or thinking about) a developer's package to allow
interfaces to other machines. I got a postcard in the mail a while back
informing me that the price had come down to $300/node and the speed had
improved. I called them this morning, and found the price is still $300,
the speed has been improved to 19.2K baud (dunno if that's full-duplex).
I've got some more info coming, or you can call them yourself at 1-800-624-
5296. I'm seriously considering this option myself, as it's pretty low
cost and seems to be plug-n-play.
[Update: I talked to Karen Harris, the rep for the Mass. area, and she
told me that it does 19.2K baud full duplex, goes 100-125 feet opstructed,
500 feet unobstructed, and has been known to do 1000 feet line-of-sight.
You can configure standalone repeaters as well to cover larger areas. The
developer's package has been put on hold, but they are thinking about
Eunuchs support...]
2) Ham radio gear. If you know anything about electronics and don't mind
spending a week or two studying operating procedures and frequency limits,
get a Technician-class license. The FCC has recently dropped the Morse
Code requirement for this class, and you get all priviledges above 30 MHz.
Then get a couple of radios and TNCs and run 1200 baud (or configure lots
of other options like 9600 baud, 56K baud, or even megabit links). The ham
radio option also allows you to transmit standard TV pictures, which can
solve the "How do I get video back from my model?" question at the same
time. I expect my teleoperated vehicle (Waldo for those of you who got my
documentation) to use packet and ATV.
3) Motorola R-Net
Motorola makes a "$300 package telemetry radio", 3x3x2 inches, 10 oz., 2-5
watts, but I haven't been able to get any information (much less a return
phone call) from them. I last tried to get ahold of a Bill Huhn in the
Radius division at (708) 576-7207. I'll let yuo know if I ever hear any
more. This one requires a license, but Motorola helps you do the
groundwork for it.
4) RC-232 adapters.
My name for putting RS-232 over a standard Radio-Control (R/C) link. While
the link normally passes Pulse Position Modulation signals, a little work
with a soldering iron gives you RS-232! So far I managed to send data at
2400 baud for a few moments (before my transmitter battery died), but
that's probably the limit, and long distances (I had the transmitter and
reciever on the same bench) may require lower baud rates. This would have
been pretty expensive ($200-300) if I hadn't had the parts lying around,
but the receiver is pretty small and light and only requires 5 volts. Let
me know if you want any more information. The main problem with this stuff
is the manufacturers won't release schematics, so you really have to know
what you are doing and be prepared to spend a lot of time playing. The
advantage is that it's license-free and has a range of a kilometer or so.
I'll post more info later when I have a chance to do some real testing.
Willie Smith
smith@sndpit.enet.dec.com
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