What is a link budget and what factors does it include?

• A. An accounting of all gains and losses from transmitter to receiver, including transmitter power, antenna gains, path loss, and receiver sensitivity.
• B. Only the antenna size.
• C. Only the transmitter power.
• D. Only the receiver sensitivity.

Answer: (B)

A link budget is a balance sheet for the radio path, showing all gains and all losses from the transmitter to the receiver. It starts with the transmitter’s output power, includes gains from the transmitter and the antennas, and then subtracts losses such as feeder/cable losses, connector losses, polarization mismatches, and the path loss that grows with distance (free-space loss plus any atmospheric or obstructions). The result is then compared to the receiver’s minimum detectable signal (receiver sensitivity) to determine if the link will be reliable. In short, a link budget accounts for transmitter power, antenna gains, all losses along the path, and the receiver’s sensitivity (and often additional margins) to ensure the received signal is strong enough.