When the radio finds a site that has sufficient signal strength, it attempts to register as a "Roamer".
The radio monitors signal strength constantly and when the strength falls below a set threshold, the radio starts searching for a site with a stronger signal.
If the radio finds a stronger signal, it attempts to register to that site.
When a radio registers on a site, whether it is a home or roam site, it is also given an "almanac" of nearby neighbor site frequencies via DFA broadcast (direct frequency assignment) allowing radios the ability to Roam in large Systems bigger than the Seed List capability or when System Frequency/Channel changes have occurred without having to physically reprogram the Radio.
As it exhausts the almanac, it starts on a "seed list" which are frequencies of all or most sites in the PassPort Radio network.