How many satellite phones were operating in Chechnya at the time? It's not like the handset was beam forming or performing fancy modulations to look like static.
In the right frequency--in publicly known frequencies--the handset would shine like a torch.
To clarify: if a satellite phone of a particular manufacturer uses a known set of frequencies and is talking to a specific satellite and you know the rough area where you are looking for phones from that manufacturer you can filter out the rest of the electromagnetic radiation and then all you are left with is instances of phones of that type (or other devices using the same set of frequencies).
It's not quite as easy as picking out a torch at night and to get accurate coordinates you will need to do some more measurements and some math but this is all definitely doable, especially if the call lasts for more than a few minutes if the device you use to scan for the phone is mobile (such as on a plane) because with every passing second your baseline is getting longer (and thus your accuracy).
https://en.wikipedia.org/wiki/Direction_finding
Radio amateurs do this sort of thing for sport, it's called fox hunting ( https://en.wikipedia.org/wiki/Transmitter_hunting ), and with experienced hunters it can be done pretty quickly if the target is stationary.
I've done some digging and this pretty important information (if true) was added unsourced in this edit:
https://en.wikipedia.org/w/index.php?title=Dzhokhar_Dudayev&...
It probably should be removed without any kind of reference to corroborate it, it's been more than 15 years since that edit has been made and there is zero evidence for this.
Probably but not _necessarily_ - if someone's vocal cadence was somehow visible in the encrypted modulation then that could be an identifier.
If that’s correct, it required decryption.
However, that Wikipedia page continues “Dudayev's phone signature and coordinates were also reportedly passed to the Russians by the NSA after U.S. President Bill Clinton's meeting with Russian President Boris Yeltsin”, so it may have been specifics of his phone (if so, what? Slight frequency and/or timing deviations that fingerprint a specific device?), not of his voice.