Bird Technologies 429-83H-01 Series-Manual - Manual (Page 9)

TX RX Systems Inc. Manual 7-9439-6 09/03/09 Page 1
GENERAL DESCRIPTION
Your TXRX Systems Inc. Tower Top Amplifier Sys-
tem provides the highest degree of reliability avail-
able in a Tower Top Amplifier (TTA). The system
uses quadrature-coupled amplifiers (also called
balanced amplifiers) to create a redundant ampli-
fier configuration in both the tower box and the
receiver multicoupling unit (MCU). Each quad-
amplifier provides two simultaneously used, essen-
tially parallel paths of amplification. Failure of one
of these paths of amplification results in an overall
gain reduction of only 6 dB.
The system also supplies automatic backup-ampli-
fier switching in the tower top box. Fault detection
circuitry continuously monitors the DC power oper-
ation of the primary quad-amplifier and automati-
cally switches to the identical secondary quad-
amplifier if conditions indicate a primary malfunc-
tion. If the secondary quad-amplifier malfunctions,
operation switches to whichever quad-amplifier is
still providing some gain due to operation of one of
its amplification paths. Fault detection circuitry also
provides at-a-glance status reporting, with front-
panel LED’s and an LCD display. The system
specifications for the tower top amplifier are listed
in Table 1.
Figure 1: Front view of the tower-top box (door removed for clarity).
Amplifier / Filter
Assembly
3-21548
Surge
Suppressor
8-21514
Door
Clamp
Surge
Suppressor
8-21183
Surge
Suppressor
8-21549
Tuning Screw
DO NOT ADJUST
Parameter Specification
Bandwidth 792 - 824 MHz
Noise Figure 2.9 dB typ, 3.5 dB max
3rd order IIP > 15.0 dBm
TTA Net Gain Fully settable by
electronic attenuator
Rejection 110 dB Min, 120 db Nom
@776 and 851 MHz
AC Current
(model 429-83H-01-M)
340 mA (typ) @120 VAC
DC Current
(model 429-83H-01-M-48)
780 mA (typ) @ 48 VDC
Table 1: System specifications.
13 dB TTA Net Gain and
maximum 6 dB transmission line loss assumed