>> >>>> The phone and the base station have to negotiate the spreading code
>>>> used for each session. If you can eavesdrop on that negotiation, you
>>>> _can_ predict the frequency hops, rendering it 'trivial' to track as a
>>>> third-party listener.
>>> Sure, except that the negotiation is typically performed by the base
>>> and handset via a wired connection OR at extremely low power (since it
>>> only happens when they're physically connected)
>> What happens if you turn the handset off, then back on, when it is
>> _out_ of the base?
> The claim about "negotiating the spreading code only when they're
> physically connected" is plainly false: if it were true, the
> multi-handset phones now so popular simply wouldn't work. After all,
> each handset has its own charging stand; only one of these is the > "base".
It really depends on the phone. I know this because in electronics class in highschool one of the students managed to clone one (and either handset worked independently with the same base, but if you placed either phone on the base, the other would stop functioning)
Not all sets work this way, but in general renegotiation isn't required to maintain security, as long as the original negotiation is performed securely chances of a spread spectrum phone being eavesdropped upon is extremely low.
Obviously not all phones operate the same way.