Which factor most directly determines the achievable wireless range for a given transmitter and receiver?

• A. Path loss.
• B. Modulation index.
• C. Antenna color.
• D. Receiver bandwidth.

Answer: (A)

The main idea is the link budget: how much the signal attenuates as it travels from transmitter to receiver. Path loss is the distance- dependent reduction of signal power due to spreading, obstacles, and other environmental effects. For a fixed transmitter power and receiver sensitivity, the maximum distance at which the received signal stays strong enough to be decoded is set by how much loss occurs over that path. In other words, the amount the signal weakens with distance directly determines the achievable range.

Other factors influence how well the received signal can be decoded once it arrives, but they don’t set the fundamental distance limit as directly. Modulation index mainly affects how the information is carried and the needed SNR for a given error performance, not the basic power budget. Antenna color has no impact on RF propagation. Receiver bandwidth changes the amount of noise and the required SNR, which can affect reliability at a given range, but the distance limit itself hinges on path loss.