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You are here: Home > Wifi Calculations > System Performance

System Performance Calculations

  1. Calculator normalises all distances to miles and feet during calculations.

  2. Free space loss = 36.56 + 20Log10(Frequency) + 20Log10(Dist in miles)

  3. mW to dBm = 10Log10(milliWatts) + 30

  4. dBm to mW = 10(dBm/10)

  5. RX Power = Margin - RX sensitivity

  6. Theoretical margin = TX power budget + RX power budget - free space loss

  7. SAD factor = Theoretical margin/TX power budget * 100 and shows the percentage of spare power on transmission.

System Performance

This calculator will give you one of three answers:

  1. If you leave distance blank it will apply the defined SAD factor (or default to 30%) to the Operating Margin and supply the max. distance (in Km and Miles) at which the Margin operates.
  2. If you enter the distance it will calculate the Operating Margin and the SAD factor.
  3. If you enter distance but leave RX or TX antenna gain (or both) blank it will apply the chosen SAD factor (or default it to 30% if none supplied) and generate the required antenna power. If both are left blank it will calculate a symmetrical antenna gain.
To RESET any parameter just set it to BLANK before clicking 'Calculate'

Notes: RX Sensitivity is ALWAYS expressed as a negative dBm (- dBm) and is the lowest power of signal your radio can handle. Its buried somewhere in your radio spec and will be typically in the range of -70 to -110 dBm. Don't guess or 'fudge' this number.

Note: If you solve for TX antenna (you leave it blank) and define a specific SAD factor it is applied to the TX budget and any TX antenna value will include this factor. If you then click Calculate again without changing anything, the SAD factor will be calculated to include the supplied TX antenna value and thus may show a lower value than the original one.

Calculations and equations used.
Frequency Distance   Result
 MHz  Km
OR

 Miles
(FS Loss)  dB
TX Power TX Cable TX Antenna  
 dBm
OR
 mW
 dBm  dB  dB
RX Sensitivity RX Cable RX Antenna  
 dBm  dB  dB  dB
Margin RX Power SAD Factor Theoretical Margin
 dBm  %  dB
Streakwave Wireless/EchoTech Wireless
1435 S. 4800 W., Suite #300
Salt Lake City, UT 84104
801.649.6400
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