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Especially due to the simultaneous operation of analog and digital television transmitters, the spectrum that is now available for wireless microphones is severely limited in many countries.

 AnalogTV channel (8 MHz wide)
 Transmission frequency of an RF wireless microphone
                                                           (200 kHz wide)
 Digital TV channel (8 MHz wide)

Figure 4: Current use of the UHF range by analog and digital TV channels as well as by wireless audio transmission equipment

Furthermore, there is a growing international tendency to restrict the range of the UHF spectrum available for TV channels in favor of new services such as DVB-H (Digital Video Broadcasting - Handheld).  New regulations that facilitate the granting of non-regularly used frequencies to new primary users such as mobile communications service providers will further reduce the frequencies that can be technically used for audio transmission.

 New Services
 Transmission frequency of an RF wireless microphone
                                                           (200 kHz wide)
 Digital TV channel (8 MHz wide)

Figure 5: The future use of the UHF range by digital TV channels, wireless audio transmission and new services

It is clear that a further reduction in frequency resources for audio transmission is to be expected.

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