Installation Manual

Release 3.3, Revision A 1/99
Installation 45
3-4.8 Optional Voltage Standing Wave Ratio (VSWR) Check
The VSWR check should be performed by the organization responsible for the antenna installation. The purpose of the
check is to ensure the integrity of the antenna and the antenna connection by determining whether the reflected power
reading is higher than the recommended value. The reflected power is defined as a ratio of the power output versus
the reflected power return. This value is determined by two key factors: the power output from the WAVEXpress/BTS
(approximately 2 watt 33dBm) and the loss due the length and type of the cable.
The recommended test approach is to use an in-line, forward/reverse power meter (ex. NAS model by Roche and
Schwarz) installed between the BTS and the antenna cable. This approach validates that the antenna and cable are
good. It also verifies that the transmit power from the BTS is within tolerance limits. The VSWR ratio should be less than
or equal to 1.5:1.
Listed below are threshold values assuming a VSWR of 1.5 at different levels of cable loss (due to length or cable type).
The estimated return loss should be greater than or equal to the values below.
Table 3-1:
Total acceptable return loss for cable loss (dB), assuming an antenna VSWR of 1.5
End-to-end cable Loss
(dB)
123456
Return Cable loss (dB)
-14 -16 -18 -20 -22 -24
NOTE
☛
Antenna types are site specific. Cable types in Asia tend to be either 7/8 inch foam
connection dielectric or RG214.