User's Manual

2. Preliminary Decisions
AMPS EAC-2100 Manual: (Draft, 02/01) Page 2-11
2.4.3 Measuring Signal Level and Isolation
To verify the correct placement and alignment of the antennas, it will be necessary to measure
the signal level from the donor cell site (on the selected donor DCCH channel) and the isolation
between the various antennas to ensure they meet the required levels.
To measure the donor DCCH signal level:
• Connect a communications service monitor or some other frequency selective measuring
instrument to the D1 antenna; monitor the DCCH channel from the donor cell;
• Adjust the orientation of the D1 antenna to peak this reading; at least -75 dBm is required.
To measure antenna isolation:
Antenna isolation can be measured using a spectrum analyzer and a tracking generator. These
functions are often combined in cellular communications monitors.
The tracking generator output is applied to the coax connector going to one of the system
antennas, while the spectrum analyzer input is connected to one of the other system antennas.
The tracking generator output level should be set to maximum (usually about 0 dBm), with the
spectrum analyzer set to check both the transmit and receive ends of the band. If a 0 dBm signal
is used as the source, the dBm reading on the analyzer will be equal to the amount of isolation
achieved between the two antennas.
F NOTE: Isolation is usually frequency dependent, with several nulls and peaks possible
in each band. The highest peak in either band defines the minimum isolation that is
achieved with a particular antenna installation.