RF Link Budget
Received power and margin from TX power, gains, distance, and losses.
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The engineering
Everything in dB so the multiplication becomes addition — the whole reason the decibel exists. Margin under 10 dB on a terrestrial link is asking the weather for permission; 20 dB is engineering.
The card is free-space: add real-world terms (rain, foliage, multipath fade) into the losses box, because the physics line is the *best* case.
Where this math comes from
The link budget is the Friis formula (1946) dressed for accounting. It matured in the microwave-relay and early-satellite era: when Telstar (1962) had watts of power and thousands of kilometers to cover, adding gains and losses in dB columns was how you knew the picture would arrive.
Deep-space work made it an art form — a Voyager downlink budget closes with single-digit margin across 20 billion kilometers, every dB argued over.
- 1946Harald T. FriisTransmission formula — the budget's physics.
- 1962Telstar / Bell SystemSatellite links make dB-column budgeting standard practice.
- 1977NASA/JPL Deep Space NetworkVoyager budgets prove the method across the solar system.
See the full timeline of the math behind every calculator →
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