Little larger than a tobacco tin, the pocket receiver pictured below is ideal for sports fans who want to hear the play-by-play broadcasts while watching a game or meet from the stands. The set employs a super-regenerative circuit, using a 958 tube that operates successfully on very low plate voltage. Around the cigar-box-wood case, a loop antenna is wound, consisting of thirty-five turns each side of center, with both sections wound in the same direction. Use No. 40 d.s.c. wire. The two 140-mmf. variable condensers, of the air-padder type, should be mounted with screws before the loop is wound. A brass bushing 1/4" in diameter and 3/8" long is soldered to the stub shaft of each condenser. A medium-size flash-light cell serves as an "A" battery, while the "B" is composed of four "fountain-pen" cells in series. The latter should last almost indefinitely as the drain is very small. Although the set is decidedly not a distance getter, since it has limited voltage and only a tiny directional loop, it should give good results up to fifty miles on the bands between 650 and 1260 kc.
You can stow this midget receiver in a coat pocket. Note the parts arrangement at the right. Cigar-box wood forms the cabinet, and a loop antenna is wrapped around it, while flash-light cells to power the set are carried in the base.
Wiring diagram also gives full parts specifications.
Follow this rear view of the set when placing the parts. Below, the crystal detector with cap removed.
SINGLE dial operates this novel one-tube battery radio; turning the set on when it is rotated to tune in stations and turning it off when moved to its minimum setting. This automatic switching is accomplished by coupling the condenser shaft to an inexpensive rheostat which has been altered by flowing solder over the winding as shown in the sketch. The circuit is easily wired.
A crystal detector is followed by a single stage of audio amplification. One 45-volt "B" battery provides the plate voltage and a single 1.5 volt dry cell serves the filament. Of the three antenna connections, Terminal A3 is the most selective, while A2 provides the greatest volume. Terminal A1 connects a trimmer condenser into the lead for a short antenna.
How the automatic switch is fashioned from a rheostat.