1. Frequency Bands For Wireless Systems

Existing wireless microphone systems transmit and receive on a specific radio frequency, called the operating frequency. Individual radio frequencies are found in frequency "bands" which are
specific ranges of frequencies. Use of radio frequencies in the United States is regulated by the FCC (Federal Communication Commission). The FCC has designated certain bands of frequencies and certain frequencies in those bands for use by wireless microphones, as well
as by other services. In the US, the frequencies used for wireless audio systems may be grouped into four general bands or ranges: low-band VHF (49-108 MHz), high-band VHF (169-216 MHz), low-band UHF (450-698 MHz) and high-band UHF (900-952 MHz). VHF stands for "Very High Frequency," UHF stands for "Ultra High Frequency." (See Figure 3-1.)



The FCC further determines who can operate in each band and who has priority if more than one user is operating. "Primary" users include licensed broadcasters (radio and television) and commercial communications services (2-way radio, pagers, and cellular telephones). Wireless microphone operators are always considered to be "secondary" users. In general, priority is given to primary users: secondary users may not interfere with primary users, and secondary users may be subject to interference from primary users. On the subject of licensing, it should be noted that
while manufacturers must be licensed by the FCC to sell wireless equipment, it is the responsibility of the operator to observe FCC regulations regarding their actual use. We will briefly describe each band and its advantages and disadvantages for wireless microphone system operation, based on the designated users of the band, the physical characteristics of the band, and the regulatory limitations of the band