User's Manual

Appendix A. Radio Signal Propagation
BreezeNET BU-DS.11/RB-DS.11 A-3 User’s Guide
For example: If, due to attenuation, half the power is lost (P
out
/P
in
= 1/2),
attenuation in dB is -10 x Log (1/2) = 3
dB
Path Loss
Loss of power of an RF signal traveling (propagating) through space. It is expressed in
dB. Path loss depends on:
• The distance between transmitting and receiving antennas
• Line of sight clearance between the receiving and transmitting antennas
• Antenna height
Free Space Loss
Attenuation of the electromagnetic wave while propagating through space. This
attenuation is calculated using the following formula:
Free space loss = 32.4 + 20xLog(F
Mhz
) + 20xLog(R
Km
)
F is the RF frequency expressed in Mhz.
R is the distance between the transmitting and receiving antennas.
At 2.4 Ghz, this formula is: 100+20xLog(R
Km
)