A method and radio receiver for determining where at least one frequency hopping radio frequency transmitter is located with respect to a set range measured from a synchronized frequency hopping radio frequency receiver. Each frequency hopping radio frequency transmitter periodically transmits an...http://www.google.de/patents/US5722059?utm_source=gb-gplus-sharePatent US5722059 - Radio receiver for use in a radio tracking system and a method of operation thereof 
