Sigh! When the BC235 came out we were endlessly berated for designing a radio that required the user to program all the voice channel frequencies. Since Motorola radios only needed the control channel frequencies we were roundly chastised.I tried to explain about the various bandplans and the necessessity of resolving the ambiguity between a frequency and the multiple channel assignments possible, depending on the band plan. But, people still weren't happy. So we capitulated and gave the masses what they wanted: The ability to trunktrack Motorola systems without having to enter all the voice channels. The complaint now is that you still need knowledge of the frequencies used, in order to select the correct bandplan. Well, we told you that way back when the '235 came out.
When a Motorola radio is programmed it too must have the correct bandplan specified. What can I tell you? This is just the way it works. Most of the systems in the United States use the default band plan so it's not that big of a problem for most users. Additionally, most of the systems have had their frequencies published anyway. Even if the list is out of date, the band plan determined by those frequencies will almost never change.
The primary utility of CC only mode is that you don't need to know when a new frequency has been added or subtracted. Trunked system operators often add or delete frequencies. Sometimes they swap frequencies with an adjacent system. Even if you aren't using CC only mode, you won't necessarily figure this out: If a single channel in a 30 channel system is deleted it is unlikely you will notice it right away. You'll occasionally miss some calls and replies but probably chalk it up to any number of other factors.
If however, you are using CC only mode you will never notice the difference, (unless you watch the frequencies displayed), because you won't miss any calls or replies. As I mentioned, when the system is programmed by the radio techs, they select the bandplan dictated by the frequencies assigned to the system. If the system adds new frequencies, they will be frequencies which do not require a change in the bandplan because that would require all subscriber radios to be reprogrammed. No one wants to do that. Consequently, adding or subtracting frequencies is almost always completeley transparent to the users. That is also the case with the BC780 if you are using it in CC only mode. As I mentioned, there are lists of frequencies for almost every trunked system out there. It doesn't matter if the lists are out of date. Modifications to the list almost never change the bandplan, so figure it out from whatever list you have available. The rules are pretty straightforward. In fact, an ambitious programmer who wants to make a name for himself could write a little program to read in a list and spit out the bandplan. I imagine it won't be long before bandplan information is just as readily available as talkgroup IDs are now.
Here are the rules for those without the manual.
PLAN 1:
If the last three digits of ALL the frequencies in use end in one of the following three digits (125, 375, 625, or 875) use Plan 1.
PLAN 2:
If the last three digits of frequencies less than 8690000 end in one of the following three digits (125, 375, 625, or 875) AND if ANY other frequencies end in (000, 250, 500, or 750) use Plan 2.
PLAN 3:
If the last three digits of ALL the frequencies in use end in one of the following three digits (000, 250, 500, or 750) use Plan 3.
PLAN 4:
If the last three digits of frequencies less than 8660000 end in one of the following three digits (000, 250, 500, or 750) AND if ANY other frequencies
end in (125, 375, 625, or 875) use Plan 4.
Greg Knox