Calculate the complete link budget for a wireless link including gains and losses.
A wireless link budget adds every gain and subtracts every loss along the signal path, in dB, to predict the power arriving at the receiver: received power = Tx power + Tx antenna gain + Rx antenna gain − path loss − cable/connector loss. The link margin (received power minus receiver sensitivity) indicates how much headroom the link has — a positive margin means the link should work, and a larger margin means more tolerance for fading, rain, or other unmodeled losses.
Received power
received_power = Tx_power + Tx_gain + Rx_gain − path_loss − cable_loss
Link margin
margin = received_power − receiver_sensitivity
EIRP (Effective Isotropic Radiated Power) is the transmit power as seen in the direction of maximum antenna gain, after accounting for cable loss: EIRP = Tx power + Tx antenna gain − cable loss. Many regulatory bodies cap EIRP rather than raw transmitter output power.
A margin of at least 10-20 dB is commonly recommended for outdoor point-to-point links to account for rain fade, seasonal foliage changes, and minor alignment drift; indoor short-range links can often tolerate a smaller margin since conditions are more stable.
Path loss is typically calculated separately (e.g. using free-space path loss or a terrain-aware propagation model) and entered here as a single dB value — see the Fresnel Zone or Microwave Link calculators for how to estimate it for a specific distance and frequency.
Path loss models the loss of the wireless signal traveling through the air between antennas, while cable loss is the separate, physical loss in the feedlines and connectors between the radio and the antenna itself — both reduce the usable signal but come from different sources.