Listen Technologies 863.050, User Manual

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15
Design Guide
Key Concepts in Designing a Stationary FM System
Multiple Channels
Guidelines for multiple channels in multiple and single spaces.
Example #1
A museum patron walks to an exhibit and needs to listen to one channel at a time.
In general, such systems work very well because of what is called “capture effect”. A Listen receiver will lock
onto or “capture” the strongest FM signal. If the receiver is near a dominating transmission signal, it will ignore
other interference – even if it is on the same channel. In theory, you can have an infi nite number of
transmitters operating in this scenario. However, to reduce the possibility of the receiver accidentally receiving
interfering transmissions, use the following guide lines:
• Reduce the transmission power on the rear of the LT-800 Stationary Transmitter to the lowest level possible.
• Get the transmitting antenna as close to the receivers as possible.
• Increase the squelch threshold on the receivers if necessary.
• Choose adjacent broadcast channels with the highest channels spacing. Try to get the channel spacing to
be at least 300 KHz apart.
• Receiver DX and Local –
DX Mode – Both strong and weak channels will be automatically tuned. This will increase the range of
the transmission.
Local mode – Only strong channels will be automatically tuned in.