Measurements
44
Average power is the most important measurement of any transmission system
since the average power is normally specified on the operating license. It is also
valuable as a maintenance tool, showing overall system health, and for
calibration.
Figure 32 Average and Peak Envelope Power - Square Wave Signal
VSWR
All Sensors
VSWR measures the relation between forward and reflected average power. The
Bird Wideband Power Sensor calculates the VSWR from the Forward and
Reflected Average Power measurements. Rho and Return Loss are also the same
measurement, but in different units:
Rho
VSWR
Return Loss (dB)
The health of the feedline and antenna systems can be monitored using VSWR
measurement under full power operating conditions. High VSWR is an indicator
of feed line damage, overtightened cable or feed line clamps, or antenna
changes/damage due to weather conditions, icing, or structural damage to the
tower.
Average Power
Peak Envelope Power
0 W
50 W
100 W
Rho
P
R
P
F
=
VSWR
1
+
1
–
------------
=
ReturnLoss dB
10
P
R
P
F
log
=
