BreezeNET DS.11 Series User Manual
C-2
PdBm = 10 x Log Pmw
For example: 1 Watt = 1000 mW; PdBm = 10 x Log 1000 = 30 dBm
100 mW; PdBm = 10 x Log 100 = 20 dBm
For link budget calculations, the dBm convention is more convenient than the
Watts convention.
Attenuation Attenuation (fading) of an RF signal is defined as follows:
Figure C-2: Attenuation of an RF signal
Pin is the incident power level before attenuation
Pout is the output power level after attenuation
Attenuation is expressed in dB as follows: PdB = -10 x Log (Pout/Pin)
For example: If, due to attenuation, half the power is lost (Pout/Pin =
1/2),
attenuation in dB is -10 x Log (1/2) = 3dB
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(FMHz) + 20xLog(RKm)
F is the RF frequency expressed in MHz.
R is the distance between the transmitting and receiving antennas (expressed in
Km).
At 2.4 GHz, this formula is: 100+20xLog(RKm)