Why do towns constantly use a different frequency for their TRS control channel? I know some towns where the control channel frequency changes daily. In other towns in changes about weekly? Why not just always keep it on the same frequency?
The original thought was to balance the wear on transmitters (back in the good old Tube days).
Then to make sure you did not have a standing failure of your "back-up" control channels.
Now, just to piss you off personally. (Or however the technician or system manager wants to do it for whatever reasons he/she feels are important enough to worry about.)
Some systems are configured to move the control channel to avoid interference. In other words, it may be because the operator is playing around with the system or it may occur because of ducting, skip or interference from a distant neighbor licensed to the same frequency.