Eighty years ago this month, the March 1937 issue of Popular Science showed how to put together this receiver, which undoubtedly provided armchair copy of local broadcast stations. The author, Clark Maxwell, (not to be confused with James Clerk Maxwell of Maxwell’s Equations fame) explained that he had tried for several years to find a convenient but inconspicuous place for the radio in his living room. He decided to solve the problem once and for all by designing this set to hang on the arm of his favorite reading chair.
He billed the set as the “Arm-Chair Five,” due to the fact that it had five tubes inside. The radio itself consisted of three tubes, since one served as the rectifier. The fifth “tube” was actually a ballast to drop the voltage of the filament chain.
The circuit was a TRF, with one 6K7 serving as RF amplifier. A 6J7 and 25A6 served as audio amplifiers to drive a speaker.
The author used the set with a 25 foot indoor antenna, although he noted that an outdoor antenna could be used.
Since the chassis was “hot,” he stressed that under no circumstances should an external ground be used. The set was encased in a wooden box covered with fabric to match the chair.