Bird Technologies 429-83H-01 Series-Manual - Manual (Page 28)

TX RX Systems Inc. Manual 7-9439-6 09/03/09 Page 20
Caution: During this test on-air sig-
nals will NOT pass through to the
station receivers.
1) The signal generator and SINAD meter (or bit
error rate meter if appropriate) should be con-
nected to the system as shown in Figure 18.
2) Be sure the signal generator is setup for a 3
KHz deviation with a 1000 Hz tone (analog) or
proper pattern for BER testing.
3) From the default display, use the ARROW but-
tons to scroll to the TEST menu choice then
press the ENTER button to bring up the test sub
menu’s.
4) Use the ARROW buttons to scroll over to the
TERMINATE LNA “A (or) B” menu choice
(depending on which amplifier is currently
active) and press the ENTER button to switch
the amplifiers input from the antenna to the
load. The “TEST TTA OFFLINE” message will
appear. The RF signal path through the tower
top box will be interrupted and on-air signals will
not be passed to the station receivers.
5) Adjust the signal strength from the signal gener-
ator until the 12 dB SINAD or required BER
point is acquired. This determines the systems
static sensitivity without the presence of site
noise. This value should be recorded in the
MCU’s memory for future use.
It is very important that sensitivity
always be measured to a recog-
nized benchmark such as bit rate
error (BER) or SINAD. Do not use
your ear or other subjective tech-
niques.
6) Press the front panel CANCEL button. This will
switch the amplifier input back to the antenna
and will return you to the default display.
If left unattended, after about 9
minutes the input of the active
amplifier will automatically switch
back to the antenna and on-air sig-
nals will again pass through to the
station receivers.
7) From the default display, use the ARROW but-
tons to scroll to the SENSITIVITY menu choice
then press the ENTER button.
NOTE
NOTE
Actual Sensitivity is calculated using the following formula:
Actual Sensitivity (dBm) = IS (dBm) + TC (dB) + TP (dB)
Where:
is the Injected Signal Level
is the Test Cable Loss
is the Test Port Loss IS
TC
TP
LEV
LO
LO
Example:
If the Test Cable for the system is 200 ft. long with a loss of 3.6 dB per 100 ft., then the Test
Cable Loss will be 7.2 dB. The Test Port Loss is Fixed at 45 dB. If the Injected Signal acquires
BER or SINAD at a level of -71.8 dBm, then the Actual Sensitivity would be -124 dBm.
LEV LO LO
Figure 17: Calculating actual sensitivity (both static and effective).