BIRD 428B-83H-01-C-110, Инструкция по установке и эксплуатации

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TX RX Systems Inc. Manual 7-9487-3 05/05/11 Page 34
1) From the TEST sub-menu display use the
ARROW button to scroll over to the UNTERM
LNA “A (or) B” menu choice and press the
ENTER button.
2) If you choose to un-terminate the input of the
active amplifier the system will return you to the
TEST sub-menu. This is the normal behavior of
the system, having the input of the active ampli-
fier un-terminated. If you choose to un-termi-
nate the input of the non-active amplifier then
the “Test TTA Offline” message will appear.
The RF signal path through the tower top box
will not be interrupted and on-air signals will
continue to be passed to the station receivers.
If left unattended, after about 9
minutes the system will switch out
of the test mode and back into the
normal mode of operation.
3) Pressing the CANCEL button returns you to the
default display.
SYSTEM TROUBLESHOOTING
System problems fall under these main categories:
1) Performance problems characterized by poor
receiver sensitivity and possibly accompanied
by activation of the alarm system. RF interfer-
ence or component problems can be the cause.
2) Hardware problems.
3) Power Supply.
Performance Degradation
Most performance difficulties manifest as an inter-
mittent or continuous loss of effective receive
channel sensitivity sometimes accompanied by
audible interference in FM systems or dropouts in
digital radios. Sensitivity loss on a continuous basis
is more likely to indicate a hardware problem which
may produce an alarm condition.
Table 9 is a trou-
bleshooting guide that is read from top to bottom to
narrow down the possible causes. The guide con-
tains both symptoms and suggested tests as out-
lined earlier in this manual. Both the measurement
of sensitivity and observation of the output spec-
trum are key tests along with the presence of any
alarm condition.
NOTE
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.