A six tube tuned radio frequency (TRF) receiver employing 201A triodes. Only one tube is in place. Circuit has three radio frequency stages, a detector and two audio stages with transformer coupling.

Portland, Ore. — Researchers at Cornell University have created the world's smallest mechanical oscillator that is capable of being tuned electrically. The nanoelectromechanical system (NEMS), which ...

Five tube tuned radio frequency (TRF) receiver employing Meyers RAC-3 type tubes. Circuitry consists of two RAC-3 type tubes as untuned radio frequency amplifiers, a single 201A detector (missing) and ...

There was a time when only the richest ham radio operators could have a radio with a panadapter. Back in the day, this was basically a spectrum analyzer that monitored a broad slice of the ...