The SRF-39 is a portable AM/FM radio made by Sony. It uses a single AA battery, as its analog electronics draw very little current. It was one of the first radios to use the CXA1129 30-pin integrated circuit, which later was responsible for the SRF-59's sensitive and selective performance.
A variant of the SRF-39, the SRF-39FP, has a transparent case, designed to thwart contraband concealment. The radio often appears on the commissary lists of U.S. federal prisons, hence the "FP" suffix. Both are popular in the DXing community partly for their generous recessed area for the tuning thumbwheel, 0-10 log strip, and guard chain.