User's Manual

Appendices
E1 Spread Spectrum Radios
10-17
10.8 RSL and Link Budget
The received signal level (RSL) can be estimated using the following formula:
RSL (dBm) = P
out
– FL
1
+ G
1
+ G
2
– FL
2
– L
P
Link budget or SOM (dBm) = RSL – Sensitivity of system
where: P
out
is the transmitter output power (in dBm)
FL
1
is the feeder loss of the transmit side (in dBm)
G
1
is the gain of the transmit antenna (in dB)
G
2
is the gain of the receive antenna (in dB)
FL
2
is the feeder loss of the receive side (in dB)
L
P
is the Path loss, defined by:
L
P
(dB) = 96.6 + 20 log
10
F + 20 log
10
D
where: F = Frequency in GHz (1.5, 2.4 or 5.8)
D = Distance of path in km
This link budget is very important for determining any potential problems during installation. We suggest that
link budget should be more than 20dB and then the link status would be stable and transmission would be
perfect. If you have calculated the expected RSL, you can see if it has been achieved during installation, and
troubleshoot if necessary.
Figure 10-6 RSL and Link Budget