page_title: Radio hat
section_title: Circuit description
hierarchical_section_title: Radio hat / Circuit description
caption_attribution_description: English: Radio-Electronics, June 1949, Volume 20, Number 9, From page 33. The two tube radio receiver cost $7.95 and was manufactured by the American Merri-Lei Corporation of Brooklyn, N.Y. The radio was powered by an external battery pack.
context_page_description: The radio hat was a portable radio built into a pith helmet that would bring in stations within a 20-mile radius. It was introduced in early 1949 for $7.95 as the "Man-from-Mars Radio Hat." Thanks to a successful publicity campaign, the radio hat was sold at stores from coast to coast in the United States.
  The radio hat was manufactured by American Merri-Lei Corporation of Brooklyn N.Y. The company was a leading supplier of party hats, noise makers and other novelty items. Its founder, Victor Hoeflich, had invented a machine to make paper Hawaiian leis while still in high-school, and by 1949 the company shipped millions of leis to Hawaii each year. An inventor and gadgeteer, Hoeflich continued to develop and even sell machinery that manufactured paper novelty items.
  Battery-operated portable radios had been available for many years, but Hoeflich hoped a radio with innovative packaging and a publicity campaign could be a runaway success. The transistor had just been invented, but was still an expensive laboratory curiosity; the first pocket transistor radio was still 5 years away.
context_section_description: Radios at this time usually were powered by the AC mains. They used vacuum tubes that had a 6 or 12 volt filament supply that heated the cathode; and a 100 to 300 volt anode (or B+) supply. The technological advances in World War II for mobile radios produced inexpensive low power vacuum tubes. The radio hat had an external battery pack that provided 1.5 volts for the filaments and the 22.5 volt B+ supply. These were much safer voltages for use in a hat, especially since the full plate voltage is dropped across the earphone. This technique was commonly used in many simple radios, some having ninety or more volts present across the head or earphones. The battery pack would power the radio for up to 20 hours.
  The radio received the AM broadcast band (540 kHz to 1600 kHz) and was tuned by a knob between the two tubes. (Table top or console radio receivers of the day used 5 or 6 tubes to provide better performance.)
caption: The circuit was on a flexible liner that fit inside the hat.
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