Listen Technologies 863 MHz Portable Radio User Manual


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9
Design Guide
Key concepts in designing a portable FM system
As mentioned on page 5, multipath can occur with portable RF systems. The audio quality of the
transmission can decrease with the occurrence of multipath. Here are a few potential improvements that
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Eliminating Multipath
Squelch
Squelching the receiver will mute the audio output when the signal from the transmitter is turned off or
the signal is too weak to be received. Without squelch you would hear radio noise in your earphone with
no RF signal present. “Tightening” the squelch will turn the receiver off if it is chattering because of
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range between transmitter and Receiver.
Transmitter power level
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The lower the power setting, the less range the transmitter will broadcast. Decreasing the broadcast range
will force the receivers to remain closer to the transmitter. To maintain an RF signal, the higher power
settings will increase range between transmitter and receiver thus introducing a higher probability of
multipath.
Multiple Portable Systems
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Squelch
Much like a multipath situation, “tightening” the squelch on the receiver will mute the audio output when
the signal is too weak to be received. Tightening the squelch will help with force the receiver to squelch
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Transmitter power level
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power could help decrease the amount of interference if there are many frequencies being used in the
vicinity.
Spacing of channels
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channels further from each other.
DX/Local
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