The Operational Directives specify what channels will be used for certain operations. The IC may also make channel assignments. Failure to monitor and transmit on the correct channel may jeopardize mission operations. For example, command will usually designate a channel for litter operations. If you transmit on this channel while a litter evacuation is underway, you may interfere with critical commands and endanger the subject or other team members.
Repeaters
While most of the channels used by EPCSAR are direct (used to directly talk between one team radio and another), some channels are assigned to repeaters. A repeater is a combination receiver and transmitter station that receives a low-power signal and automatically retransmits at a higher power. Repeaters are useful if two teams can communicate with the repeater but not with each other. As shown in the illustration, Team 1 is blocked from direct communication with Team 2 by terrain. However, Team 1 can transmit to the repeater, which in turn transmits the message to Team 2.
We typically use repeater channels, like channel 1, when driving to get county-wide coverage. In the field, we often use direct channels, like channel 2, since other team radios are nearby and the repeater station may not be visible. Repeater channels are paired up with direct channels so that one can listen (but not talk) on both channels simultaneously. The important thing to remember is that if one of the paired channels doesn’t work, try the other channel. Currently, the repeater/direct channel pairs are 1/2, 4/5, and 8/9.
