Manual 7-9415-1.4 Page 12
TX RX Systems Inc. 08/31/06
61-65-50 UserMan page 12 of 24
4) Referring to figure 4, connect the generator test
lead to one side of the signal distribution system
(external antenna) and the spectrum analyzer
lead to the other (internal distribution system)
and observe the signal level. The difference
between this observed level and 0 dBm is the
isolation between the sections. If the signal is
too weak to observe, the spectrum analyzer's
bandwidth may have to be narrowed and its
input attenuation reduced. Record the isolation
value.
The isolation value measured should
exceed the signal booster’s gain figure by at
least 15 dB.
It is wise to repeat the procedure listed above for
measuring antenna isolation with the signal gener-
ator set to frequencies at the passbands edges in
order to see if the isolation is remaining relatively
constant over the complete width of the passband.
Repeat the isolation measurements at the other
passband in bi-directional systems and use the
lesser of the two values to determine the maximum
gain setting.
Increase Isolation or decrease gain?
Modification of the signal distribution system is
required to increase isolation between the up and
downlink path. This will require significant changes
that may or may not be practical from a cost or
logistical standpoint. Gain reduction may be the
only alternative but this is easy to achieve with Sig-
nal Booster II. Gain for both the uplink and down-
link path can be set from 50 to 80 dB. Here are the
steps to follow.
1) Subtract 15 dB from the measured isolation
between uplink and downlink branches of the
antenna/signal distribution system. This is the
maximum usable gain level for both the uplink
and downlink path.
2) Accessing the user menu through the front
panel, set the gain of the uplink path to the level
determined in step 1. A detailed explanation of
how to negotiate the menu system is given on
page 14.
3) Repeat step 2 for the downlink path.
INTERNAL
SIGNAL DISTRIBUTION
SYSTEM
SPECTRUM
ANALYZER
EXTERNAL
ANTENNA
SIGNAL
GENERATOR
ZERO LOSS
REFERENCE
ISOLATION (dB)
Figure 4:
Typical test equipment interconnection for measuring antenna isolation.
