Atomic Taco wrote:
King County is also going to go to a shuffled band plan after the reband. Here's how it works now:
...
I think the main reason they're switching is to prevent hacked radios from jumping on the system. In order to transmit each radio will need this special key.
Shuffled band plan (which was a standard compnont of MPT1327 since 25+ years ago) offers greater efficiency as well as significant flexibility, should future "rebanding" or changes to the band take place. MPT did it because the span of frequencies at 400-512 MHz was simply too great to build a DFA (direct frequency assignment) table, as is currently used in several of the trunking protocols.
Depending on how it is implemented, it could also accomodate wierd offsets (or not).
Passport uses different DFA "bands", but this restricts any given "site" (the site controller can host multiple "sites" of differing bands) as well as subscriber units to one range of freqs. The makers of Passport (and Passport radios) had to update a few years ago when the 406-420 band went to a standard 9MHz offset.
When they went after VHF (where there is no standard offset) they simply diddled the framing of their control data to send a DFA number for TX and for RX.
It would be interesting to learn if Motorola offers this along with the shuffled plan.
I think the feature called "hard key" is what keeps bootleggers off their system, but there are much more knowledgeable folk here to answer that.