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Audio Technologies

Audio Technologies. Waveform. The image of the oscillation Amplitude= the height or depth of the signal from the time baseline Frequency= number of wave crests that pass a fixed point in a given period of time Phase=half wavelength. Amplitude Modulation.

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Audio Technologies

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  1. Audio Technologies

  2. Waveform • The image of the oscillation • Amplitude=the height or depth of the signal from the time baseline • Frequency=number of wave crests that pass a fixed point in a given period of time • Phase=half wavelength

  3. Amplitude Modulation • amplitude modulation = varying the amplitude of a carrier to create an analog of the original signal; i.e., changing the heights of the signal in relation to the time baseline.

  4. Frequency Modulation • Frequency modulation= varying the frequency of a carrier to create an analog of the original signal

  5. Signal Propagation • AM and other short wave frequencies, two types of radio waves gets the signal over the horizon from the site of the antenna • Groundwaves • Skywaves: Kennelly-Heavyside layer (called skip). • FM and higher use direct waves

  6. AM Radio Channels • 117 channels in AM 535 to 1705 with AM signal 10 Khz wide. • The extra 10 were added in 1993 for moving existing stations (1705-535=1170 divided by 10=117 channels). • a station at 760 KHz transmits a signal from 755 Khz to 765 KHz with the carrier at 760).

  7. AM Channels • Class A stations 60 channels operate unlimited schedules on clear channels (10 to 50KW) • Class B stations 51 channels unlimited schedules on clear or regional channels (.25 to 50KW)

  8. AM Channels • Class C stations 6 local channels (1,000 watts to 250 watts) • Class D stations daytime, limited time or low powered. Directional night time (less that 250 watts). Not protected from interference and protect class A & B stations

  9. FM • FM has 100 channels from 88 Mhz to 108 Mhz [88.1 to 107.9 channels 201 to 300] • each channel is 200 KHz wide, which is why there are no even FM stations. • E.g., WUAL transmits at 91.5 MHz but its signal stretches from 91.4 to 91.6 MHz.

  10. FM Class A Channels • FM consists of 20 Class A channels (all zones). • Class A stations effective radiated power (ERP) up to 3,000 watts • antenna HAAT (Height above Average Terrain) of no more than 300 feet. These stations cover about 15 miles.

  11. FM Class B Channels • There are 60 Class B (zone I IA) stations that • transmit at 50,000 watts and • 500 feet HAAT. • Cover about 30 miles.

  12. FM Class C Stations • Class C stations (zones II) • transmit with up to 100,000 watts • HAAT of 2,000 feet. • This normally gives a coverage area of about 60 miles. There are 20 channels at the lowest part of the FM spectrum for nonprofit, noncommercial radio stations

  13. Noncommercial FM • There are 20 channels at the lowest part of the FM spectrum for nonprofit, noncommercial radio stations

  14. Ribbon Microphone

  15. Typical Ribbon Microphones • RCA BX 44 • RCA 77 DX

  16. Dynamic Microphone

  17. Typical Dynamic Microphones • Shure SM 57 and E-V 635A

  18. Condenser Microphone

  19. Lavalieres • RCA BK 12 A (dynamic) & Beyer Dynamic

  20. Omnidirectional

  21. Uni and Bidirectional

  22. Cardiod

  23. Tape Heads

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