User's Manual

63
6.1.3 Path Loss Considerations
The path loss is the amount of attenuation the radio signal undergoes between the two ends
of the link. The path loss is the sum of the attenuation of the path if there were no obstacles in
the way (Free Space Path Loss), the attenuation caused by obstacles (Excess Path Loss)
and a margin to allow for possible fading of the radio signal (Fade Margin).
capabilityseasonalfadeexcessspacefree
LLLLL
<
+
+
+
_
Where
spacefree
L
_
Free Space Path Loss (dB)
excess
L
Excess Path Loss (dB)
fade
L
Fade Margin Required (dB)
seasonal
L
Seasonal Fading (dB)
capability
L
Equipment Capability (dB)
Equation 1 - Path Loss
6.1.4 Definitions
Sensitivity: Sensitivity is defined as the combined receive input signal level on both horizontal
and vertical inputs that produces a Null BER Error ratio of 3x10
-7
.
Output Power: The output power shown is for a centre channel in Region 1. The output power
will be reduced on the edge channels and may vary if different region codes are selected.
AMOD Threshold: The AMOD threshold is the combined receive input signal level on both
horizontal and vertical inputs that results in the link consistently entering the receive
modulation mode under consideration as the signal level is increased.
System Threshold: Thresholds for all modes except BPSK are for the relevant link
optimization AMOD thresholds. System threshold for BPSK is the RPSK receive sensitivity.
Max Link Loss: The maximum link loss for each modulation mode is derived from the AMOD
threshold for that mode (sensitivity threshold for BPSK) and the maximum Region 1 centre
channel output power. The figures assume integral antennas with 23 dBi gain are used.