You can locate a ham radio operator by searching for the name or call sign in the Federal Communications Commission license register at ARRL.org. You can often locate foreign operators by searching on QRZ.com. You can find ham radio operators in your area by contacting a local radio club; these are listed on the American Radio Relay League website.
Amateur radio operators must register a valid mailing address with the Federal Communications Commission under part 97.23 of the FCC regulations. All amateur transmissions must be identified by a call sign in accordance with part 97.119. This allows anyone to find the location of any ham radio operator. Foreign operators have similar obligations under International Telecommunications Union regulations, so it is possible to locate them through an international contact bureau or their national communications regulatory body.
Radio hams are permitted to operate away from their home location, so you may not be able to locate the exact source of a particular transmission. In this case, you can find their location using radio direction finding equipment. Direction finding equipment uses an array of antennas in a differential or Doppler configuration to ascertain the distance and direction to a transmission source. Radio direction finding is a useful technique for identifying the cause of radio interference or locating the source of unlawful transmissions.