User's Manual

61-89A-50-A18-G1-UserMan page 11 of 20
TX RX Systems Inc. Manual 7-9352 (version 4) 01/27/04 Page 11
to provide extended coverage. In most cases, a
signal booster with far less gain than the first is
required.
f) Improper installation or application of signal
splitters or directional couplers in the signal dis-
tribution system. This is usually the cause of too
low a signal level but deserves mentioning here.
Signal splitting needs to be done with constant
impedance signal splitters so that the proper
power splitting ratios and VSWR are main-
tained. Using tee connectors by themselves is
inviting trouble. Directional couplers must be
connected with regard to their directionality and
coupling levels or improper system signal levels
may result.
Procedure for Measuring Input Signal Levels
1) Set a spectrum analyzer for the center fre-
quency of one of the signal boosters pass-
bands.
2) Set the analyzers sweep width so that the entire
passband frequency range can be observed.
3) The analyzers input attenuator should be set in
order to observe input signal levels from
approximately -80 dBm to 0 dBm.
4) Connect the analyzer to the section of the sig-
nal distribution system that is going to serve as
the input (see
Figure 3
).
5) Record the power level (in dBm) of all carriers in
the passband frequency range that are signifi-
cantly greater than the noise floor displayed on
the analyzer.
6) To find the total power being applied the calcu-
lations listed below must be performed. The
conversion chart at the rear of the manual can
be used. Here are the steps:
a) Convert all values in dBm to Watts
b) Total the power for all carriers in Watts
c) Convert the total power in Watts to dBm
Example:
suppose we have a signal
booster with a maximum gain of 70
dB. After checking the input signal
levels, it was determined that there
are three signals that are signifi-
cantly greater than the noise floor displayed on the
analyzer. These signals have strengths of -45
dBm, -43 dBm and -41 dBm.
First we use the conversion chart at the end of this
manual to convert the power levels in dBm to watts
S p e c t r u m A n a l y z e r
R a d i o 1
R a d i o 2
S I G N A L D I S T R I B U T I O N S Y S T E M
Figure 3
: Typical test equipment setup for measuring input signal levels.