[45910] in Cypherpunks
Re: FH radios
daemon@ATHENA.MIT.EDU (John Lull)
Mon Dec 25 11:15:33 1995
From: lull@acm.org (John Lull)
To: cypherpunks@toad.com
Date: Mon, 25 Dec 1995 16:06:55 GMT
In-Reply-To: <v01530512ad01d78bc507@[206.86.1.35]>
On Sat, 23 Dec 1995 08:20:28 -0800, Steven Weller wrote:
> Thus in a frequency-hopping radio you can push the retuning (read RF
> phase-locked loop) technology to its limit and build transmitters and
> receivers around them. These typically hop in the order of 100 times a
> second. The adversary has to find the uncorrelated signal very quickly
> indeed *and* have PLL technology at least as good as yours to recover
> anything from it. Finding the signal generally means listening to all
> frequencies at once, requiring huge amounts of hardware parallelism and/or
> realtime computing power. Once you throw ten or so radios onto the same
> band, it's no longer any use looking for the strongest signal, making that
> approach useless.
This is nowhere near the limit of the technology. 15 years ago, I was
working on PLLs that would stabilize within a couple degrees of final
phase within 3.5 microseconds. That permits you to do useful work at
100,000 hops per second.
