Definition
A link budget is the full accounting of every gain and loss along a radio path, used to predict the power arriving at the receiver and confirm a link will actually close. Starting from the transmitter output power, you add antenna gains and subtract cable losses, free-space path loss, and any obstruction or weather penalties. The result is the expected received signal level, which you compare against the receiver's sensitivity to find the leftover margin.
How the math works
The basic relationship is received power equals transmit power plus transmit antenna gain minus path loss plus receive antenna gain, all in decibels. The single largest term is usually free-space path loss, which grows with both distance and frequency. The difference between predicted received power and receiver sensitivity is the link margin; experienced operators want a comfortable margin so the link survives rain, foliage growth, and seasonal changes rather than failing at the first storm.
Why it matters for sovereign comms
For off-grid Bitcoiners deploying LoRa or point-to-point microwave to move data without infrastructure, the link budget is the planning tool that decides antenna choice, mast height, and node spacing before any hardware is hauled up a hill. LoRa's exceptional sensitivity, able to decode signals below the noise floor, effectively buys extra budget that ordinary modulation cannot.
A link budget ties together several RF fundamentals. See Attenuation (RF) for the loss terms, dBm for the units it is computed in, and Yagi Antenna for adding directional gain.
In Simple Terms
A link budget is the full accounting of every gain and loss along a radio path, used to predict the power arriving at the receiver…