Find someone with a running TRS-80. Bring your favorite portable AM radio with you. Have your friend run a program, and while that's occurring, put your radio

Find someone with a running TRS-80. Bring your favorite portable AM radio with you. Have your friend run a program, and while that's occurring, put your radio next to the machine and start tuning it around. It won't take long before you find one of the (many) harmonics emitted by the computer.