link budget

A link budget is a simple accounting sheet for a radio link: start with the transmitter power, add every gain (antennas, amplifiers) and subtract every loss (cables, path loss, fade margin) along the way, and the number left at the end tells you how strong the signal arrives at the receiver. It is the bank-statement view of wireless — does enough signal survive the journey to be heard above the noise?

Because every quantity is in decibels, the whole calculation reduces to addition and subtraction rather than messy multiplication. Engineers compare the predicted received power against the receiver's sensitivity (the faintest signal it can decode); the leftover difference is the link margin, the safety cushion for rain, fading, and bad luck. A satellite link with a 3 dB margin is living dangerously; a well-engineered one carries 6–10 dB.