Link budget
Account for gains and losses, then compare received power with your receiver’s requirement.
Additional gains & losses+3 dB net · 5 terms
Drag to reorder · Edit for name, type or position.
Drag a grip to move a term, including across path loss. Use Up or Down arrows on the grip, or click it to choose a position. Escape cancels a drag.
- Transmitter outputStartStarting power: 10 dBm
- Cable and connector loss between the transmitter output and antenna.
Loss · Cable & connectors
dBRunning level: 8 dBm - Antenna gain in dBi toward the receiver.
Gain · Toward receiver
dBiRunning level: 11 dBm - Combined polarization mismatch or other link loss, counted once.
Loss · Mismatch & system allowance
dBRunning level: 11 dBm - Free-space path loss−80.23 dBRunning level: -69.23 dBm
- Antenna gain in dBi toward the transmitter.
Gain · Toward transmitter
dBiRunning level: -66.23 dBm - Cable and connector loss between the receive antenna and receiver input.
Loss · Cable & connectors
dBRunning level: -67.23 dBm - Receiver inputResultReceived power: -67.23 dBm
Intermediate levels may be isotropic-equivalent budget values. Moving terms changes their accounting order, not received power.
Remaining margin
24.8 dB
Meets the entered requirement
- Received power
- -67.23 dBm
- Required receive level
- -92 dBm
Margin = received power − required level.
The required level includes your margin. Link availability is not predicted.
Power calculation
Start before the transmit feed. Add each gain and subtract each loss to reach the receiver input, after its feed.
- Transmitter output
- 10 dBm
- Transmit feed
- −2 dB
- Transmit antenna
- +3 dB
- Polarization / system
- 0 dB
- Free-space path loss
- −80.23 dB
- Receive antenna
- +3 dB
- Receive feed
- −1 dB
- Receiver input
- =-67.23 dBm
Design limits & more results
- Required transmitter outputFor the entered path
- -14.77 dBm
- Maximum path lossFor the entered transmitter output
- 105 dB
Each limit meets the receiver target, including the required margin, with the other budget terms fixed.
- Path loss
- 80.23 dB
- Received power in watts
- 189.19 pW
- Margin above sensitivity
- 27.77 dB
- Receiver sensitivity
- -95 dBm
Model & assumptions
Start with transmitter output and add every gain , then subtract every loss , including path loss. The resulting receive level is :
Power levels are in dBm; gains and losses are in dB, with antenna gains referenced to isotropic antennas in dBi. Enter losses as non-negative magnitudes. Calculate free-space path loss or enter a known path loss.
Transmitter power is taken before its feed cable; received power and sensitivity refer to the receiver input, after its feed cable. Count each loss once: if an entered path loss already includes a cable or other loss, leave that loss out of the additional terms.
Calculated free-space loss assumes an unobstructed path with both antennas in each other’s far field. It does not estimate extra losses from obstacles, fading (changes in signal strength) or equipment. Enter those as separate loss terms when needed.
Receiver sensitivity is the minimum receive level for the stated performance. Adding the required margin raises the target receive level:
Sensitivity and the target are in dBm; margin is in dB. If sensitivity is derived from noise, the tool uses equivalent noise bandwidth, source noise temperature, 290 K-referenced receiver noise figure and required SNR at the final receiver input. Gain/loss rows do not calculate added noise.
Remaining margin tells you how far the calculated receive level is above that target:
Zero or positive remaining margin meets the entered requirement; it does not guarantee link reliability. The optional transmitter-power and path-loss limits vary one quantity while holding the others fixed.
For example, −95 dBm sensitivity plus 3 dB required margin sets a −92 dBm target. A received level of −67.23 dBm leaves approximately 24.77 dB of remaining margin.
Does a result look wrong? Report a calculation issue
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