But the units that Ned uses, *as I recall*, cost ~$1k ea. They work by sending out a return pulse that is something like 200mhz less than the signal received. This prevents the sending unit from locking on. mike miller - renton,wa 91 200q > These things are all a crock, >> > > >Why don't you ask NedRitchie how much of a crock they are... ;-) >stealth mode... > >sean. >