Bird Technologies 429-83H-01 Series-Manual - Manual (Page 34)

TX RX Systems Inc. Manual 7-9439-6 09/03/09 Page 26
common component such as a transmission line or
antenna is damaged.
LIGHTNING & LIGHTNING ARRESTERS
The tower box uses three lightning arresters: one
on the antenna port, one for the main transmission
line and one for the test line. Although no practical
amount of protection can prevent catastrophic fail-
ure as the result of a direct hit, the lightning arrest-
ers are very effective in preventing damage from
nearby strikes and smaller direct hits. Lightning
arresters do not last forever and can eventually fail,
especially after a direct hit. A damaged arrester
can cause low gain with known-good A and B
amplifiers. An arrester with lightning damage will
exhibit increased insertion loss, poor return loss
and may appear as a DC short on the main or test
lines.
VANDALISM
Damage to the TTA caused by hunters or target-
shooters in remote locations is not uncommon.
Penetrating bullets may open or short transmission
lines. Operating voltages are applied to the tower
top box by the main transmission line. In addition,
the main transmission line carries RF, so serious
damage to this cable can prevent system opera-
tion. The system will operate normally if the test
transmission line becomes damaged but there will
be a loss of system testing and an alarm will be
continuously set.
AC Line Fuse (Model 429-83H-01-M)
A failure of the power supply will obviously shut the
tower amplifier down because of high signal loss
through the tower box and MCU. The power supply
is located on the MCU chassis and has a replace-
able 250 volt, 2 amp fuse for the AC line. The sup-
ply has a green status LED located next to the
connectors which illuminates when the supply is
turned on.
DISCONNECTED CABLES
If a faulty connection occurs in any segment of
either the main transmission cable, test cable, or
the CAT-5e cables the system responds with a
fault indication. In the case of the CAT-5e cables
the fault could occur in either the cable which runs
between the rear of the MCU and the bulkhead
lightning arrester or the cable which runs between
Loss of Sensitivity (Intermittent / Continuous)
Individual Receive Channel(s) affected All Receive Channels affected
Intermittent Continuous Intermittent Continuous
Measure Sensitivity Measure Sensitivity Measure Sensitivity Measure Sensitivity
Small to moderate loss of
sensitivity
Small to severe loss of
sensitivity
Small to moderate loss of
sensitivity
Small to severe loss of
sensitivity
Do spectrum analysis Do spectrum analysis Do spectrum analysis Do spectrum analysis
Two or more carriers > 35 dBm
when desense occurs
On-channel TX stuck on and
visible in spectrum.
One carrier > 35 dBm when
desense occurs then Carrier
Desense Interference likely.
Possible Alarm condition
Other-channel modulation
heard in FM system or dropouts
in digital system
Defective cable / connector /
Receiver
Carrier(s) < 35 dBm when
desense occurs then Transmit-
ter Noise Interference likely.
Check operation with amplifier
A and B. Failed amplifier gives
low sensitivity on 1 amplifier
only.
Intermodulation Interference
likely
If operation is the same on
amplifier A or B, Defective com-
mon component is likely
Table 9: Troubleshooting Guide for TTA systems with degraded performance. Shaded blocks indicate common possible cause.