Listen Technologies LT- 800-072 - Manual (Page 17)

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RF Reception
Setup InstructionsQuick Reference
Speci
fi cations
Package ContentsPackage Contents
RF Reception
The antenna for the LT-800 can be mounted directly on the unit if desired. However, you may
find that the unit will provide better performance when the antenna is located elsewhere. If you
plan to mount the antenna in a different location other than the top of the unit, you must use
cable and connectors rated at 50 ohms. Although cable used for cable TV installations looks
similar to this cable, it will not work with your Listen system.
If you need to run cable over a length greater than 50 feet for 216 MHz applications or greater
than 100 feet for 72 MHz applications or to maximize broadcast range, Listen recommends that
you use RG-8 cable rather than RG-58. RG-8 is a lower loss cable, meaning that more of your
signal will reach the antenna.
Long cable runs can result in signal degradation due to the “loss” characteristics of the cable.
When using RG-58 with a 72 MHz transmitter, there is an average* loss of 4 dB per 100 feet of
cable and at 216 MHz using RG-58 an average* loss of 8 dB per 100 feet of cable. (A 3dB loss
means half of your power has been lost.) However, it is better to suffer coaxial power loss than
to try to shoot your signal through obstacles! Obstacles, especially metal, can create drop-outs
or reflections of your signal that will result in poor listening conditions.
*NOTE: There are many varieties of 50 ohm, RG-58 and RG-8 cables. You may purchase a
cable that is better or worse than this value. Please check with the cable vendor or
manufacturer for exact specifications.
For proper and dependable operation, Listen receivers need to receive a strong and consistent
signal from the originating transmitter. Note that on portable receivers the headset wire is the
receiving antenna. The following strategies should be used maximize this signal:
When designing and installing your system, keep in mind that the location of both the
transmitting and receiving antennas is critical to maximize broadcast range.
Eliminate or minimize obstructions between the transmitting and receiving antenna.
Minimize the distance between the transmitting and receiving antennas.
Move transmitting and receiving antennas away from metal or conductive objects.
Place the transmitting antenna as high as possible.
Orient both transmitting and receiving antennas vertically.
Position the RF Power switch on the back of the LT-800 to full RF Power, unless lower power is
necessary (see page 9).
Keep coaxial cable from transmitter to antenna as short as possible.
CAUTION: When installing antennas, ensure the antenna is clear of power lines.
Coaxial cable, connectors, and optional antenna mounting kits are available from Listen. See
page 22-23, visit www.listentech.com or ask your dealer for details.
RF Reception Maximization Strategies
Coaxial Cable
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