How many aircraft can operate on a DME frequency before congestion occurs?

The correct answer is based on the operational capabilities and limitations of Distance Measuring Equipment (DME) systems. DME operates in the UHF frequency range and provides distance information to aircraft from a specific ground station. The DME system can handle a certain number of aircraft simultaneously without experiencing congestion or interference.

Typically, DME systems are designed to accommodate approximately 100 aircraft using the same frequency in a given area. This number is based on how the DME signal can be effectively processed and also on regulatory standards that ensure safe separation in navigation systems. Once the number of simultaneous users exceeds this threshold, the likelihood of signal congestion increases, which can lead to misleading distance readings or degraded performance.

Therefore, the operational limit of around 100 aircraft effectively allows for a reliable level of service without risking data integrity or safety.