TX RX Systems 434B-83H-01-M-110/48, Инструкция по установке и эксплуатации

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7;5;6\VWHPV,QF Manual 7-9547-1 12/09/14 Page 22
TTA NET. The second amplifier, located on the
base control unit is used to overcome the losses
associated with distribution.
When the tower top amplifier system is installed
there are detailed adjustments and test procedures
which must be followed in order to insure optimum
performance of the system. The process includes:
Attenuation Settings
Spectrum Analysis
Operational Tests
Sensitivity with Load Connected
Sensitivity with Antenna Connected
Operational testing must be performed in a
methodical manner to provide the correct perfor-
mance evaluation and ensure that the information
obtained is correct. For each procedure it is impor-
tant that the data be recorded accurately and is
available anytime assistance is required or when
performance is in question. Before a receive sys-
tem problem is suspected, the appropriate opera-
tional tests must be performed. Before operational
tests for sensitivity can be verified, the programma-
ble attenuation settings and spectrum analysis
must be performed. If these are not correct, the
sensitivity and degradation may appear out of toler-
ance.
ATTENUATION SETTINGS
The system contains programmable attenuators for
optimizing the TTA NET and adjusting the receiver
multicoupler distribution. Both of these attenuators
must be adjusted as part of the system installation.
The attenuation adjustments allow the system to
maintain maximum protection of the receivers,
while obtaining the best sensitivity possible.
TTA NET Gain
TTA NET is defined as the net gain between the
input of the tower top LNA and the input of the sta-
tion receiver. The amount of programmable attenu-
ation that your system requires in order to reach an
ideal amount of TTA NET Gain will vary depending
on the length of your main transmission line and
the loss of the short (pig-tail) cable between the
base control unit and the radio.
Setting the Attenuators
The system has two programmable attenuators
including the TTA NET Gain Attenuator and the
Distribution Attenuator. These attenuators need to
be adjusted such that the gain from the input of the
tower top LNA to the input of the station receiver
equates to
15 dB
.
The TTA NET Gain Attenuator is preset at the fac-
tory for 6.0 dB and the Distribution Attenuator is
factory preset to 4.0 dB. These settings are appro-
priate for 0 dB of Main Line Loss and 1 dB of Pig-
tail Loss.
Table 5
indicates how to set the attenua-
tors for any other case.
Attenuator changes are done through software
interface via the menu select keys. Your setting will
be stored in system memory until you change it
again even if the equipment is powered down. To
adjust the value perform the following steps.
1) Press the DOWN ARROW button on the front
panel to scroll through the menu choices until
you reach the ATTENUATORS menu.
Figure 13
: Alarm terminals. Normally open and normally closed terminals are available.
Alarm
Terminals