What is a link budget and how do you calculate it?

Link budget accounts for all gains and losses in a communication link to ensure adequate received signal. Calculation: Pr = Pt + Gt - Lp + Gr - Lother, where Pt is transmit power, Gt/Gr are antenna gains, Lp is path loss (free space: 20*log10(4*pi*d*f/c)), and Lother includes cable losses, atmospheric effects, and margins. Link margin = Pr - receiver sensitivity. Design must ensure positive margin under worst-case conditions. Link budgets are essential for system design, determining required power, antenna sizes, and maximum range.