A jammer must have access to the receiver's antenna.

• A. Line of sight to the target area
• B. Access to the receiver's antenna
• C. Knowledge of encryption keys
• D. GPS timing signals

Answer: (B)

Direct interference must be injected into the receiver’s input path to be effective. The antenna is the entry point for RF signals into the receiver, so having access to the receiver’s antenna (or its feed) allows the jammer to couple energy directly into the front end and overwhelm the desired signal. Without access to the antenna, you’d rely on radiating nearby or in the environment, which is far less efficient due to path losses and poor coupling into the specific receiver, making jamming far less reliable. The other options don’t provide a way to force the receiver to misbehave: just being in line of sight to the target area doesn’t guarantee that the jammer’s signal reaches the receiver’s input, and encryption keys or GPS timing signals are unrelated to injecting interference into the front end.