User guide

Anticipating RF Signal Loss Engineering Your RF Communications
124
pmp-0229 (Mar 2013)
Calculating Rx Signal Level
The Rx sensitivity of each module is provided at http://www.cambiumnetworks.com. The
determinants in Rx signal level are illustrated in Figure 35.
Figure 35: Determinants in Rx signal level
Rx signal level is calculated as follows:
Rx signal level dB = Tx power − Tx cable loss + Tx antenna gain
− free space path loss + Rx antenna gain − Rx cable loss
NOTE:
This Rx signal level calculation presumes that a clear line of sight is established
between the transmitter and receiver and that no objects e
ncroach in the Fresnel
zone.
Calculating Fade Margin
Free space path loss is a major determinant in Rx (received) signal level. Rx signal level, in turn,
is a major factor in the system operating margin (fade margin), which is calculated as follows:
system operating margin (fade margin) dB =Rx signal level dB − Rx sensitivity dB
Thus, fade margin is the difference between strength of the received signal and the strength that
the receiver requires for maintaining a reliable link. A higher fade margin is characteristic of a
more reliable link.