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Barrett 911 Automatic Antenna Tuner for Base Station Installations
Antenna
Various antenna configurations, such as vertical whips, long wires and loops, can
be used for base station installations, using the Barrett 911 automatic antenna
tuner. In general however the following points should be considered:-
The antenna should be mounted as far away as possible from buildings, trees,
vegetation and sources of electrical interference. If metallic masts or supports are
used, arrange insulators to ensure the antenna is spaced at least 2 metres from the
mast. Remember the radiating part of the antenna starts at the tuner. The location
of the bottom portion of the antenna is very important.
Horizontal wire antennas have maximum radiation broadside to the antenna when
the frequency is less than 1/4 wavelength. Radiation is at a minimum at the end
points of the antenna. Inverted "V" installation of horizontal antennas minimises the
directivity and is recommended for omni-directional coverage.
High voltages are present on the antenna system. The antenna tuner and antenna
should be located or protected so that there is no possibility of accidental contact.
Transceiver and Tuner Mounting
The transceiver should be mounted in a suitable position allowing easy operator
access. The antenna tuner should be mounted, preferably out of the weather, and
as close to the ground (earth) point as possible. The interconnect cable supplied
with the antenna tuner should be routed, away from other cables, back to the
transceiver and connected as indicated in the diagram. The maximum interconnect
cable should be less than 25 metres.
Ground (earth) System
The ground (earth) system is a key part of the overall antenna system and
consequently the system operation. An inadequate ground system is the primary
cause of poor performance and tuning problems. There is little point in installing
the antenna unless a good ground system can be provided. In areas of good
ground conductivity (i.e. ground always damp), an effective ground can be made
through a grounding rod. This should be approx. 3 metres in length and should be
installed as close to the tuner as possible. Several rods bonded together will
improve the ground contact. In some cases metal water pipes may be used as a
ground providing:-
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The water pipe is close to the tuner and the water pipe enters the ground
close to the tuner.
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There are no joints or couplings in the pipe that will increase the resistance
path to ground.
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The water pipe enters soil with good conductivity.
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A low resistance joint is made with the water pipe.
Frequently the ground conductivity will not be sufficient to provide a satisfactory
ground for the Barrett 911 tuner. This will almost certainly be the case in well
drained sandy soils or on rock. In these cases a counterpoise must be used as a
ground system. This will also be the case in rooftop installations where no existing
Содержание 2050
Страница 31: ...31 of 285 then press the key ...
Страница 66: ...66 of 285 then press the key type in your messages using the alpha numeric keys then press the key ...
Страница 91: ...91 of 285 use the Scroll keys to select Yes to erase the address book entry then press the key ...
Страница 93: ...93 of 285 enter the telephone number using the numeric keys up to 16 digits then press the key ...
Страница 99: ...99 of 285 then press key to save the new alias ...
Страница 110: ...110 of 285 Add an Entry press the key type in a new label using the Alpha keys then press the key ...
Страница 118: ...118 of 285 Upload pack See section Cloning programming from another transceiver ...
Страница 134: ...134 of 285 then press the key Change the Selcall format associated with the ID if required then press the key ...
Страница 172: ...172 of 285 If the operator attempts to change channels while linked the following screen is shown ...
Страница 175: ...175 of 285 If the operator attempts to change channels while linked the following screen is shown ...
Страница 186: ...186 of 285 Press the key and the first address that matches or the closest match the prefix entered is selected ...
Страница 189: ...189 of 285 Pressing the key displays the link status Or if you already have a link established ...
Страница 224: ...224 of 285 Fitting the 2050 Into the 2040 Manpack Adaptor Removing the Battery Cartridge ...