How often must you identify with your FCC-assigned call sign when using tactical call signs such as “Race Headquarters”?

Using a tactical call sign like 'Race Headquarters' or 'Checkpoint 3' is an excellent practice during public service events to efficiently identify a station's function or location. However, tactical call signs do not legally replace your actual station identification. The FCC still requires you to transmit your official FCC-assigned call sign at least every 10 minutes during an ongoing communication, and at the very end of the communication. You do not need to use your official call sign on every single short transmission within that 10-minute window, but the tactical call alone is never legally sufficient.