Wireless Calculators | Radio Frequency Propagation

Wireless Calculators

Please select a wireless calculator: Power Budget | Free Space Loss | System Performance | Fresnel Zones | Power Conversion

Disclaimer: Due to the nature of radio frequency propagation and the numerous factors that can affect operating range we do not guarantee that you will achieve any specific range for your application. These wireless calculators are for estimation purposes only. L-com does not guarantee their accuracy or applicability. L-com cannot be held liable for wireless installations based on these tools. Customers should use these tools at their own risk.

Power Budget Wireless Calculator- Total power of your system in dBm

Use this wireless calculator to determine your Power Budget. The 'Power Budget' is the the total power being output from the wireless system and is the sum of:

PLUS Radio Transmit Power
MINUS cables and connectors losses
PLUS antenna gain

Enter one parameter in each column (or leave blank) depending on what is know and the calculator will supply the appropriate conversions automatically. Up to 2 decimal places may be entered as 0.xx or .xx.

Note: Connector loss is generally minimal unless you have many of them or if your cable is very short.

See the calculations and equations used for this wireless calculator.

Radio and Antenna
Transmit Power	Antenna Gain	Power
mW OR dBm	dB(i)	dB
Cable Loss
Cable Properties (per 100 ft or m)	Cable Length
dB (100 ft) OR dB (100 m)	feet OR meters	dB
Connector Loss
Frequency in MHz	No. of Connectors
MHz.	No.	dB
Budget
		dB

Free Space Loss Wireless Calculator - Power loss over distance

Free Space Loss is the loss of power over distance (assuming no FRESNEL Effect and nothing in the way). This is a very idealised calculation and in practice everything interferes with the signal but this will give you a reasonable approximation of the actual loss over distance.

Enter the system Frequency in MHz and the distance in either Kilometers (Km) or Miles below and then click the 'Calculate' button. 1 GHz = 1000 MHz e.g. 2400 = 2.4 GHz.

See the calculations and equations used for this wireless calculator.

Frequency	Distance		Result
MHz	Km OR Miles		dB

Fresnel Zones Wireless Calculator - How much more than LOS or how high should my antenna be?

This calculator defines how much clearance you need (you will require more than simple Line-of-Sight) and for longer links > 3 Km (2 miles) whether you may have a ground clearance problem.

Enter the Total link distance (in Miles or Kilometers), if you do not enter an Obstacle distance (in Miles or Kilometers) the calculator will use the mid-point for all calculations (Note: assumes antennas at same height). Finally enter the system Frequency in MHz and then click the 'Calculate' button. 1 GHz = 1000 MHz e.g. 2400 = 2.4 GHz.

The calculator will generate the radius of the 1st Fresnel zone only (at the obstable point or the mid-point), the 60% (no obstacle) radius and the height of the effective earth curvature at the mid-point of the Total link distance using the effective earth radius.

See the calculations and equations used for this wireless calculator.

Total Link	Obstacle Distance	1st Fresnel Zone Radius
Km OR Miles	Km OR Miles	m at Km	ft at Miles
Frequency		60% No Obstacle Radius
MHz		m	ft
		Earth Height (mid-point)
		m	ft

System Performance Wireless Calculator - How far will it go, will it get there or what is my Operating Margin?

This wireless calculator will give you one of three answers:

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.
If you enter the distance it will calculate the Operating Margin and the SAD factor.
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. RX Sensativity should be listed in your radio manual and will be typically in the range of -70 to -110 dBm.

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.

See the calculations and equations used for this wireless calculator.

Frequency	Distance		FS Loss
MHz	Km OR Miles		dB
TX Power	TX Cable	TX Antenna	Total TX
dBm OR mW	dBm	dB	dB
RX Sensitivity	RX Cable	RX Antenna	Total RX
dBm	dB	dB	dB
Margin	RX Power	SAD Factor	Theoretical
	dBm	%	dB

Power Conversion Wireless Calculator - milliWatts to dBm (and vice versa)

Power in milliWatts to dBm (and vice versa) . Enter the 'Transmit Power' in milliWatts OR the 'Power Ratio' in dBm and click the appropriate 'Calculate' button. 1 Watt = 1000 milliWatts.

See the calculations and equations used for this wireless calculator.

Transmit Power		Result
mW		dBm
Power Ratio		Result
dBm		mW

Power Budget Calculations

mW to dBm = 10Log₁₀(mW)
feet to meters = .3048
meters to feet = 3.28
Calculator normalises all distances to kilometers and meters
Connectors loss = 0.10 * square root (frequency in GHz)

Free Space Calculations

Free space loss = 36.56 + 20Log₁₀(Frequency) + 20Log₁₀(Distance in miles)
Calculator normalises all distances to miles
Miles to Kilometers = 1.609
Kilometers to miles = 0.621

Fresnel Zone Calculations

Calculator normalises all distances to kilometers and meters
Miles to Kilometers = 1.609
Kilometers to miles = 0.621
feet to meters = .3048
meters to feet = 3.28
1st Fresnel Zone radius (Km) = 17.3 x Sqr root ((Obstacle Distance x (Total Link - Obstacle Distance)) / (Frequency in GHz x Total Link))
1st Fresnel Zone radius (miles) = 72.6 x Sqr root ((Obstacle Distance x (Total Link - Obstacle Distance)) / (Frequency in GHz x Total Link))
Obstacle free radius = 0.6 x 1st Fresnel Zone radius
Radius of nth Fresnel zone (meter) = sqr root ( (n x wave length x Obstacle distance x (Total Link - Obstacle Distance)) / Total Link )
wave length (meters) = speed of light (299,792,458 m/s) / frequency in Hz
Earth curvature calculation = (Total Link) ² /(8 * effective earth radius)
effective earth radius = 4/3 * Earth radius
Earth radius = 3963 miles, 6378 Km

System Performance Calculations

Calculator normalises all distances to miles and feet during calculations.
Free space loss = 36.56 + 20Log₁₀(Frequency) + 20Log₁₀(Dist in miles)
mW to dBm = 10Log₁₀(mW)
dBm to mW = 10^(dBm/10)
RX Power = Margin - RX sensitivity
Theoretical margin = TX power budget + RX power budget - free space loss
SAD factor = Theoretical margin/TX power budget * 100 and shows the percentage of spare power on transmission.

dBm to milliWatts Calculations

mW to dBm = 10Log₁₀(mW)
dBm to mW = 10^(dBm/10)

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