Issue link: https://digital.copcomm.com/i/714540
WIRELESS MICROPHONES A wireless microphone is nothing more than a small ra- dio frequency transmitter; and it has been around for a long time. The oldest example I've found is an "RCA RA- DIOMIKE" Type BTP-1A from about 1950. It weighed six pounds and had handles on both sides of the 11" high x 4 1⁄2" wide x 3 1⁄2" transmitter. Stated battery life was four hours but it took a strong person to hold that transmitter for that long a time! Those of us of a certain age remember—and not too fond- ly—the Vega systems from the 1960s. These units had a much smaller transistorized transmitter but the main problem was that the transmitter was not crystal con- trolled. The receiver had a strong Automatic Frequency Control (AFC) circuit to track the drifting transmitter. The problem was that the AFC would also respond to a stron- ger frequency and it was commonplace to hear police or taxi cab transmissions in the middle of an event. And while the worked, they never sounded very good. The next generation had crystal-controlled solid-state transmitters and used the 169 MHz–171 MHz VHF spec- trum allowed under FCC Rules Part 90.265. Eight chan- nels were specifi ed at 50 kHz bandwidth in a band shared by Bill Ruck, San Francisco Broadcast Engineer THE RADIO FREQUENCY SPECTRUM PUZZLE In order to understand what is happening with the UHF television band and how it has an impact on the use of this band for wireless microphones, one needs to take a look at several different aspects of the situation. PART 2 by Bill Ruck, San Francisco Broadcast Engineer THE RADIO FREQUENCY SPECTRUM PUZZLE In order to understand what is happening with the UHF television band and how it has an impact on the use of this band for wireless microphones, one needs to take a look at several different aspects of the situation. RCA RADIOMIKE Type BTP-1A