FlightHawk RF Test Set
70
VSWR
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.
Peak Envelope Power
Peak power measurements detect amplitude changes as a signal modulates the
carrier envelope. The WPS operates in an asynchronous cycle: 300 ms of
waveform sampling followed by a 50 ms reset period. The peak power is then
displayed and the cycle repeats. The display therefore updates about three
times per second.
Transmitter overdrive can be detected with peak measurements. Common
problems are overshoot at the beginning of burst packets, amplitude
modulation, and excessive transients. These damage system components with
excessive peak power and also cause data degradation, increasing the Bit Error
Rate. For TDMA applications, Peak and Burst Power measurements are used to
detect overshoot in single time slots. Other time slots must be turned off for this
test.
Rho
P
R
P
F
=
VSWR
1
+
1
–
------------
=
ReturnLoss dB
10
P
R
P
F
log
=
