Circa 1923, this so called pocket radio is the earliest version of a true portable radio that I know of. A 1-tube regenerative receiver using  1 UV-199 tube, battery requirements; 3-volt "A" battery (one of those extra long "D" cells) and 1-22.5 volt "B" battery. The antenna is a flat ribbon loop that's encompasses the entire outer inside of the radios electronics. Standard earphones are required for listening. One other requirement, a large, deep pocket, set measures 12.5X3X4" and weighs just over 3 lb without batteries.