Listen Technologies LT-800-216, LT-800-072 manual Channel Selection, At 72MHz, At 216MHz

Channel Selection

Channel Selection

It is important to choose channels that are free from interference to achieve proper operation of your Listen equipment. This process is trial and error. Before turning on the transmitter, listen to the wide band channels on the receivers (lettered channels at 72 MHz and channels that start with a “2” for 216 MHz when using a Listen receiver). Listen to the audio through the headphone or via the speaker and choose a channel with the least amount of interference. Unless you are interfacing with an existing narrowband transmission system, always use a wide band channel.

If you are using multiple channels follow this process:

1.Same Space If you are using multiple transmitters in the same space, the highest number of channels that will work simultaneously is six at

72 MHz and three at 216 MHz. With all of the transmitters

off, listen for interference on all the wide band channels with a

Listen receiver. Using the frequency compatibility tables on pages 15-17, eliminate any channels that have noticeable interference. Now choose the channels with the widest channel spacing. It is recommended that adjacent channels be spaced at least 300k Hz apart. If there is no interference the following channels are recommended. For a 72 MHz system, use channels A, C, E, I, J and H. For a 216 MHz system, use channels 2A, 2K and 2V.

2.Distributed Spacing If you are using transmitters that are distributed over a large area, you can achieve more simultaneous broadcast channels. However, it is critical that your receiver(s) be located as close to its transmitter as possible. You can use adjacent channels (see frequency compatibility tables (on pages 15-17) in this case as long as the adjacent channel transmitter is at least 50% further away from the receiver than the original transmitter. Example: The transmitter for the receiver on channel E is 100 feet from the receiver. The adjacent channel transmitter on channel D should be at least 150 feet away.

It is highly recommended that after channel selection has been achieved, you lock the channel so that it cannot be changed by the user. To accomplish LOCK on the LT-800, press the “UP” button for 3 seconds. Repeat the process to unlock.

Notes in regard to using 72 MHz and 216 MHz systems:

1.72 MHz is a secondary frequency band. This means that other transmitters are licensed to use these frequencies. Thus, you may experience interference from paging transmitters and other types of transmissions. You will need to find a clear channel by listening to all the wide band channels.

2.216 MHz is a primary frequency band and no other types of transmissions are authorized to use it. Thus, you will find the highest probability of clear channels in this band. However, you may experience intermodulation of the TV Channel 13 aural carrier if there is a channel 13 transmitter in your area and you are close to the transmitter. If you cannot find a clear channel in 216 MHz band due to channel 13, it is recommended that you switch to

a 72 MHz system.

Wide Band Recommendation Listen recommends that you always use a wide band channel unless you need to be compatible with existing narrow band receivers from other manufacturers. Wide band channels have lower noise than their narrow band counterparts.

At 72MHz

The LT-800 at 72 MHz operates on 17 wide band channels and 40 narrow band channels.

•Letters= Wide Band Channels

(Example: E)

•Numbers= Narrow Band Channels

(Example: 32)

At 216MHz

The LT-800 at 216 MHz operates on 19 wide band channels and 38 nar- row band channels.

•“2” as left digit= Wide Band

Channel (Example: 2C)

•“1” and “3” as left digits= Narrow

Band Channels (Examples: 1A; 3R)

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