Bird Technologies 429-83H-01 Series-Manual - Manual (Page 23)

TX RX Systems Inc. Manual 7-9439-6 09/03/09 Page 15
4) After setting the main line loss value press the
ENTER button to return back to the FEEDLINE
DATA menu. This will save your setting choice.
5) With the FEEDLINE DATA menu displayed
press the ENTER button to step down to the
MAIN LINE LOSS sub-menu. Press the UP
ARROW button to move to the TEST LINE
LOSS sub-menu.
6) Use the UP and DOWN ARROW buttons to set
the test line loss to the desired value. This stor-
age register works in a forward loop fashion,
starting at 0.0 and increasing to 9.9. A button
press after 9.9 returns the setting back to 0.
7) After setting the test line loss value press the
ENTER button to return back to the FEEDLINE
DATA menu. This will save your setting choice.
Then pressing the CANCEL button while at the
FEEDLINE DATA menu will return you to the
default display.
OPTIMIZING THE SYSTEM
In the TTA system the first stage of amplification is
in the tower top box which is used to overcome the
main line loss, develop the noise figure, and the
TTA Net Gain. The second amplifier, located on
the multicoupler deck (base unit), is used to over-
come 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 tol-
erance.
ATTENUATION SETTINGS
The system contains programmable attenuators for
optimizing both the TTA Net Gain and 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 Gain is defined as the net gain between
the input of the tower top LNA and the input of the
base LNA. The amount of programmable attenua-
tion 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.
The value of the TTA Net Gain programmable
attenuator can be adjusted either manually by the
customer or automatically by the microprocessor in
the MCU. The choice of manual or automatic is
determined by a menu choice in the Webpage
User Interface which is accessible via the MCU’s
LAN connector using a separate PC. For a com-
plete description of the Webpage User Interface
software refer to the TXRX Systems Inc. technical
manual 7-9440.
When automatic has been selected the message
“AUTO MODE” will be shown on the MCU front
panel display when you scroll down the menu
choices to the TTA Net Gain value, refer to the
menu selections chart shown in figure 7. Manual
changes to the attenuator value using the front
panel ARROW buttons are not allowed when in the
automatic mode.
Receiver Multicoupler Distribution
Receiver Multicoupler Distribution is defined as the
gain between the input of the base LNA and the
input of the station receiver. The receiver multicou-
pler distribution adjustment allows for proper com-
pensation of the MCU to receiver cable/distribution
losses and should ideally be set to unity. The
amount of attenuation that your system will require
in order to reach an ideal amount of receiver multi-
coupler distribution will vary depending on the
length of the cables from the multicoupler outputs
at the rear of the MCU to your receivers. Distribu-
tion attenuation is always adjusted manually using
the front panel ARROW buttons. There is no auto-