TX RX Systems Inc. Manual 7-9487-3 05/05/11 Page 35
Hardware Problems
Two of the most common reasons for TTA alarms
are direct lightning strikes and vandalism. Even
though the system is designed with redundancy so
that likely-to-fail components have backups, it is
possible to shut the system down, especially if a
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 & B amplifi-
ers. 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 428B-83H-01-M/C-110)
A failure of the power supply will obviously shut the
tower amplifier down because of high signal loss
through the tower box and control unit. The power
supply is located on the control unit chassis and
has a replaceable 250 volt, 2 amp fuse for the AC
line. The supply has a green status LED located
next to the connectors which illuminates when the
supply is turned on.
PERIODIC MAINTENANCE
The following procedures can be followed as part
of a periodic maintenance program.
1) TX RX Systems Inc. recommends that tests for
establishing the performance level of the sys-
tem, as outlined in this manual, be performed
every six months.
2) Because it is possible that the current alarms
may not
detect a fault affecting RF gain, we rec-
ommend measuring system sensitivity every six
months and comparing this value against the
stored value.
3) A yearly inspection of the tower box is also rec-
ommended. The box features a hinged door,
which may be opened after loosening the lock-
ing clamps. Inspect and tighten any loose con-
nectors or other hardware. Make sure the
moisture relief openings are unobstructed and
remove any accumulated condensation. It is
important to tighten the door correctly after
inspection so that the door gasket seal is main-
tained.
4) All feedline connections should be inspected for
tightness and waterproofing integrity. Water
seeping into the transmission lines will cause
system degradation.
RECOMMENDED SPARE PARTS
It is recommended that one distribution amplifier
assembly (MCU systems) be kept on hand for
emergency repairs. The part number of the distri-
bution amplifier assembly is 3-21450.
OPTIONAL EQUIPMENT
Optional equipment can be purchased from TX RX
Systems Inc. in order to increase the performance
of your TTA system. These include a narrowband
filter as well as a multicoupler expansion deck. The
narrowband filter is designed to help limit the band-
width of the multicoupler unit. The multicoupler
expansion deck will increase the total multicoupler
outputs to 32 or 48. The multicoupler expansion
deck is only used with the MCU style system.
Multicoupler Expansion Deck
There are two different optional multicoupler
expansion decks available for the 428B TTA sys-
tem including a 16 to 32 channel expansion and a
16 to 48 channel expansion.
16 TO 32 CHANNEL EXPANSION
The 16 to 32 channel optional expansion (part# 75-
83H-428B) is shown in
Figure 32
and includes a
16-way divider mounted on a 19 inch deck. The 16-
way divider is designed to be connected to the
Содержание 428B-83H-01-C-110
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