1906

AM broadcasting

• Reginald Fessenden’s first AM transmission
• in December 1900 used a carbon microphone in series
• with a rotary spark-gap transmitter
• producing ten thousand sparks per second,
• but the spark-gap transmitter was too noisy
• and too spread out over over the frequency band
• to carry clear voice transmissions,
• and the Branly or Marconi coherer
• was too crude to demodulate a voice frequency.
• So Fessenden began to work to improve
• both the transmitter and the receiver.
• He invented the process of heterodyning
• to modulate and demodulate an AM signal.
• He invented the hot wire barretter and various
• electrolytic detectors to rectify the received signal.
• He contracted with GE for the Alexanderson alternator
• to produce a high frequency radio carrier signal.

Wireless telephone

• We had Morse-code telegraphy
• by radio and by telegraph,
• and telephone networks dependent on wires.
• People did not have radios
• in their homes or in their cars.
• There were no radio broadcasts.
• So people thought of AM radio
• as a wireless telephone, not as
• a broadcast to the masses.

Dental receptionist

• Ethel Merman reported that Lucille Ball reported
• receiving radio broadcasts via temporary dental fillings
• in 1942, early in World War II.
• She was able to overhear a broadcast
• of an underground radio station from a Japanese spy
• and reported it at work to MGM security officials,
• resulting in the arrest of someone’s gardener.
• Was this a fabrication of a pair of comediennes
• or, in any case, is there a case for dental receptionists?