but, it will scan and stop on the first one it hears, good or bad, near or close. sure you could get it to look for the next one and hope it is better and keep doing that. if you want.
i tried it on the county next to me and it works. their channels do not change so it could tell which tower it was on and change it accordingly. later i just put in 6 different systems (i don't like quick keys) and used the tower names, it works fine.
Similar to the above post - what brand and model scanner are you using?
If it is Uniden, once the scanner "hears" a control channel, it disregards other control channels it hears. The only exceptions are for Uniden model scanners newer than the 396T, which have the capability to receive multiple control channels. (996T, 396XT, 996XT, Home Patrol and the x36 models).
This is probably way over simplifiying it. Those newer scanners can "handle" multiple sites on the same trunking system. With multiple sites, the scanner "knows" not to disregard other control channels (as long as they are in a separate site).