Bird Technologies 5012 User Manual

Page 4

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:

, ,

and

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.

Video Filter

Except for average power and VSWR measurements, all WPS
measurements rely on a variable video filter to improve accuracy. This
filter can be set to either 4.5 kHz, 400 kHz, or full bandwidth. It should
be as narrow as possible while still being larger than the demodulated
signal bandwidth (video bandwidth). Narrowing the filter limits the
noise contribution caused by interfering signals. Listed below are some
common modulation schemes and the appropriate video filter.

Figure 2

Video Filter Settings,

300 kHz Signal

Video Filter

Modulation Type

4.5 kHz

CW Burst (Burst width > 150 µs), Voice Band AM,
FM, Phase Modulation, Tetra

400 kHz

CW Burst (b.w. > 3 µs), GSM, 50 kHz AM, DQPSK

Full
Bandwidth

CW Burst (b.w. > 200 ns), CDMA, WCDMA,
DQPSK, DAB/DVB-T

Rho (µ) = P

⁄

Filter

Too Small

Filter

Too Wide

Correct

Filter

Noise

Signal