From: Phil Karn <karn@qualcomm.com>
Date: Mon, 7 Feb 94 21:36:43 PST
To: sdw@meaddata.com
Subject: Re: New remailer up
In-Reply-To: <9402041508.AA18037@jungle.meaddata.com>
Message-ID: <199402080532.VAA24768@servo.qualcomm.com>
MIME-Version: 1.0
Content-Type: text/plain


>You can get spread spectrum radio/data modems that do 256Kbits/sec
>(Cylink) and can go up to 30 Miles.  It is unlicensed in the US
>because it is limited to .8watts (I think).  I believe 10 miles is the
>limit with an omnidirectional antenna.  Spread spectrum should be
>pretty hard to triangulate on.  Remember that the technology came from
>unjammable military radios.

>I think you'd have to have a fairly sophisticated scanner to even pick
>it up.

Not quite. Very few, if any, Part 15 spread spectrum modems do automatic
transmitter power control, and as a result they generally run much more
power than necessary. That makes you much easier to spot. It also
pollutes the spectrum.

Even spread spectrum transmitters with tight power control (e.g, our
IS-95 cellular system) are easily detected (though not demodulated)
with simple AM scanners when you're close enough. Especially when the
mobile in question is a long way from the cell and transmitting near
full power as a result.

On the other hand, if you're not close, any particular mobile will be
drowned out by the several dozen others sharing the same channel.

Phil