After reading this thread it becomes even more apparent how misinformation gets started and then misleads people. Please people, don't comment about things that you know little or nothing about.
Not sure what you are referring to other than maybe the statements that n5ims made about duplicating ID's on a system and having the radio somehow get directed to a different talkgroup.
OK, for a better explanation of how Motorola trunking works, or at least what I was told when I say in the system training class over at Schaumburg, was that when you turn on a subscriber, it transmits an outbound signalling word on the control channel and tells the system controller that the radio is active. Mind you this is on a type 2 Smart Zone system. Might be Smart Net, I seem to always get it backwards,,, but anyway.
Now when a subscriber (portable or mobile) keys up, it again transmits on the control channel receive frequency. The system considers this an inbound signalling word. It contains the talk group ID it wants to talk on and the assigned ID of the radio. The system checks for an open channel and creates an outbound signalling word telling all other subscribers that the specific talk group is going to be on channel X. This channel number is actually a number and NOT a specific frequency. This is what is changing with regards to the 800Mhz rebanding initiative. The FCC has actually assigned all available 700, 800 and 900 pairs a specific channel number. This is the information contained in the outbound signalling word. Now, again, the controller transmits the channel number and talk group ID out on the control channel in the outbound signaling word. The radios that are on that talk group or a scanning that talkgroup tune from the control channel to the assigned channel and open squelch for lack of a better term. The transmitting subscriber begins transmitting on the input frequency on that assigned channel and the other subscribers begin receiving it. Now a dispatch console is a horse of a different color, and I am not going into how an Embassy switch works here, as it don't apply here and I ain't typing all that out. If you want to know, go look it up on the web or something.
OK, there is HOW it works with a no BS working subscriber. Scanners are a bit different but are similar ion a couple ways. The reason that you ONLY have to program control channels into the scanner and not every channel of the system is this simple. As I mentioned above, the FCC assigned every pair a specific number. So when a talk group is assigned a channel by those numbers the scanner knows where to tune to. Now this is also why the early scanners will not work correctly when rebanding takes place in your area. Case in point, a local city wide type 2 system I know of has it's control channel being reassigned. Scanners with that control channel in them will hear nothing after rebanding and in truth, hear nothing on that frequency now because it's locked out as a control channel because it's going to be changed.
Every channel is not capable of being control channel either. Typically a system will have 1 to 4 control channels. Also, with older scanners, and subscribers for that matter that are not rebanded. If a talk group gets assigned a rebanded channel, it will go to where it thinks it should go but because the frequency for that channel changed due to rebanding, there will be nothing there to listen to.
Now some final thoughts on using an actual subscriber as a scanner.
First off, the city I work in has a specific law stating that possessing a radio programmed for the public safety system is a crime. You can own all the 800Mhz type 2 trunking radios you want, you just can't program them for the cities system. A number of cities have similar laws. Some states ban scanner use in vehicles all together unless you are with public safety or a ham. It would be my guess that those areas would frown on having a full radio programmed up with their system. Now, back to the ID thing, past, present and a look forward. At least in this area. In the past there was a receive only ID that news media and such could use to access the system. The controller had it assigned so that it was not granted access to talk on any talk group but could listen to them. It was turned off and set to inhibit ANY radio (read that brick the radio) that was programmed with that ID. The system owner decided to charge per ID and began monitoring the system with advanced software so that it would see if a radio would come on the system multiple times... IE more than one radio with the same ID. When the advanced software detected this more than once, it would inhibit ALL radios with that ID. Of course the paying customer would receive a new ID, and the radio got turned back on with a new ID. I will not specifically go into how this works, but if you have a radio that gets inhibited and you are not authorized on the system, it requires the radio to be sent into the depot (Motorola equipment) and fixed. Before anyone says something silly, yes there are ways around it, but get caught doing it and you WILL have a problem with several legal departments including Motorola's.
That's how it rolls now.
A look ahead.
With newer systems comes new hurdles. Radios are becoming something else. With the newest wizbang stuff, the control channel data is changing again. Taking a page from the cell phone industry, all the newest stuff has in addition to a system administrator assigned ID will have an ESN or electronic serial number. In addition to having this ESN, it will have advanced remote control functions that can allow the system admit to track the location of the radio by GPS. So if you clone an ID, you will trigger a system alarm. The administrator will get a warning that two radios with different ESN's but the same assigned ID are on the system. At that point the admin can locate the radio via GPS, by enabling it as ALL the radios have it. And in the same action brick the radio. So the radio is sitting there, transmitting it's GPS location to the system admin and is bricked. And you CAN'T change the ESN as it's hard coded. So if you go playing that game,,,, you WILL get a knock at the door. And you and your ebay radio will be going for a free ride in a police car. Now make no mistake, if you are buying $7000 radios on ebay that are new technology, they came from somewhere and someone is probably looking for them. Either they are stolen or they are demo or prototypes that are NO suppose to be sold to ANYONE under any circumstance. I realize they are out there. But you can also buy explosives, automatic weapons without a tax stamp (ATF paper work) or anything else on a long list of illegal or stolen items.
Final word, DON"T BOTHER WITH TRYING TO USE A PROGRAMMED SUBSCRIBER RADIO FOR A SCANNER.
