Link: a Look at Time-Delay Interference

Does your simulcast radio system seem to exhibit improved range and performance when certain transmitters are turned off? In almost every case, this is an indication of improper system operation and that your system needs on-site optimization.

In a simulcast system there are several parameters that adversely can affect system performance, but one parameter that is sometimes misunderstood is time-delay interference, or TDI. In this article we begin a discussion of TDI and its significance in a simulcast radio system.

Simulcast radio systems are used when a limited number of RF channels are available and a large geographical area needs to be covered. As the name implies, simultaneous broadcast, or simulcast, occurs when two or more sites transmit at the same time on the same frequency; invariably the coverage from these multiple sites will overlap.

See the full article here: A look at time-delay interference — Urgent Communications article.