Channel 38 is reserved for this application.Frequency Lists for SHTF Survivalist Radio Communications and Preppers If you need 5 or more radio microphones, licenses will be required for the frequencies used outside channel 70. To avoid interference from intermodulation, ony 4 frequencies, which must be carefully selected can be used simultaneously within any one channel. To limit the possibility of interference and attain best audio quality, diversity receivers should be used. A separate receiver for each frequency will also be required. Unless switch to talk microphones are being used, each microphone used will need to be set at a different frequency. The user will need to to switch their hearing aid to the 'T' - Position to receive the audio. The signal is fed into the induction loop amplifier, the output device. It picks up the radio signal and converts it back into an electrical audio signal The receiver is a stationary type and is usually located close to the induction loop amplifier. FREEBAND FREQUENCIES TO AVOID FREEThe frequency is most likely to be between 863 - 864.99MHz, channel 70 as this is the only free band available to this application. The range will be any where between 30m and 300m depending on conditions. The strength and frequency of the radio signal is controlled by government regulation. The transmitter, which is built into the microphone, or worn as a body pack converts the audio into a radio signal and broadcasts it through an antennae. In this application, the input device is a radio microphone. The input device provides the audio signal to be transmitted. In this case, the radio microphones are used to replace wired microphones as they can be worn by the speaker allowing them the freedom to move around the stage as they talk. The neck loop is worn round the neck, it is basically a personal induction loop, the user will need to switch their hearing aid to the 'T' Position to receive the audio.įM System used to enhance the performance of an Induction loop system With headphones, a Hearing aid user may need to remove their hearing aid or keep the volume low to avoid feedback from the hearing aid (stop the hearing aid whistling). The output device will either be a set of headphones or a neck loop connected to the receiver. It picks up the radio signal and converts it back into an electrical audio signal. The receiver is worn by the user as a belt pack or on a lanyard. installed and typically close by to the audio input source. The transmitter converts the audio into a radio signal and broadcasts it through an antenna. In this application, the input may be from a wired microphone, TV, VCR, Computer, DVD player, mixing desk etc. An Enhanced FM Assistive Listening System With Multiple wireless microphones and other sourcesįM System used as an Assistive Listening System. FREEBAND FREQUENCIES TO AVOID PORTABLEA portable FM assistive listening system and Tour Guide.FM System used to enhance the performance of an Induction loop system.FM System used as an Assistive Listening System.Only high end radio mic systems can access this band Radio Microphones and other point to point audio links (Unusable from 2012) Shared with television also used for talkback systems as well as microphones Radio microphones (Also shared with radio astronomy) Shared with television, limited availability, used for temporary audio links as well as microphones Shared with television, limited availability, used for fixed audio links as well as microphones Shared with lots of talkback radio systems, (only high end radio mic systems can access this band) FREEBAND FREQUENCIES TO AVOID LICENSEWhere more than 4 frequencies are required, a license for channel 38 must be purchased. Due to intermodulation between frequencies, only 4 frequencies within the channel can be used simultaneously. It has a frequency range from 863MHz to 864.99MHz. The most interesting channel for assitive listening applications is channel 70 because it is free to use (unlicensed). Radio frequencies are grouped into ranges called channels.
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