All radios are now natively in the UHF band. The trunked system, well more specifically the two Broome County Simulcast cells, also operate natively in the UHF band. Those two Broome County cells are part of a larger system that covers multiple counties in the region, however each county has their own slice of bandwidth and unique frequencies, all of which are controlled by a single master controller (system core). Trunked systems are 80% computers and 20% RF these days.
That's the simple overview of how it works. There are many more details of how P25 systems actually work that you can find online if you wish to research it, but I'll explain a bit more here just for kicks.
A trunked "site" is a physical location where the transmitters (repeaters), antennas, and all the other associated hardware lives. Not all that different from a low band base station 50 years ago, the purpose is to receive and transmit RF signals. A trunked system combines multiple frequencies into a pool that is shared by all users of the system, no one frequency is exclusive to any purpose anymore. Instead the master system controller assigns frequencies seemingly at random as they are needed by radios that want to talk to each other. This maximizes efficiency, as you no longer require many discreet frequencies assigned for a single purpose, so for example you don't have an "OEM" channel with a frequency all to itself that is idle 95% of the year, which is a waste of valuable spectrum.
In the case of Broome County, and other similar trunked systems, there are multiple physical "sites" that are combined to form a cell, or a collection of sites. When combined like that, each of those physical sites is known as a "subsite", and the collection of subsites forms a simulcast cell. Simulcast because each subsite is simultaneously receiving and transmitting on the same set of frequencies to provide wide area coverage without requiring a ridiculous amount of individual unique frequencies. So instead you maybe have 10 of these subsites sharing the same 6 frequencies, as is the case with the Broome County West cell. No matter where you are within the coverage area of those 10 subsites, all of the radios (called "subscribers") are receiving and transmitting on the same pool of 6 frequencies., which dramatically improves the breadth of coverage without having to actually change over to another frequency/repeater/channel manually. The system takes care of it all for you. And if you were to drive from the western half of the county into the eastern half, then the subscriber will "roam" to the East cell and you would continue to operate seamlessly.
So in addition to the collection of frequencies that make up a trunked site or simulcast cell, you also have "talkgroups" which are the virtual "channels" that the radios/subscriber operate on. As noted earlier, no one frequency is dedicated to any particular talkgroup, instead they just rotate around the pool of available channels in a first come/first serve manner. So one transmission on the Sheriff's Dispatch talkgroup of 27210 might take place on 454.475, and a few seconds later another transmission on the same talkgroup might take place on 453.425. The system tells all of the radios on that talkgroup which frequency to tune to, it all happens in the blink of an eye.
There's a lot more to it, but that should be enough of a primer to get you some basic understand. Oh and PS it's trunking, not "trucking".
That's the simple overview of how it works. There are many more details of how P25 systems actually work that you can find online if you wish to research it, but I'll explain a bit more here just for kicks.
A trunked "site" is a physical location where the transmitters (repeaters), antennas, and all the other associated hardware lives. Not all that different from a low band base station 50 years ago, the purpose is to receive and transmit RF signals. A trunked system combines multiple frequencies into a pool that is shared by all users of the system, no one frequency is exclusive to any purpose anymore. Instead the master system controller assigns frequencies seemingly at random as they are needed by radios that want to talk to each other. This maximizes efficiency, as you no longer require many discreet frequencies assigned for a single purpose, so for example you don't have an "OEM" channel with a frequency all to itself that is idle 95% of the year, which is a waste of valuable spectrum.
In the case of Broome County, and other similar trunked systems, there are multiple physical "sites" that are combined to form a cell, or a collection of sites. When combined like that, each of those physical sites is known as a "subsite", and the collection of subsites forms a simulcast cell. Simulcast because each subsite is simultaneously receiving and transmitting on the same set of frequencies to provide wide area coverage without requiring a ridiculous amount of individual unique frequencies. So instead you maybe have 10 of these subsites sharing the same 6 frequencies, as is the case with the Broome County West cell. No matter where you are within the coverage area of those 10 subsites, all of the radios (called "subscribers") are receiving and transmitting on the same pool of 6 frequencies., which dramatically improves the breadth of coverage without having to actually change over to another frequency/repeater/channel manually. The system takes care of it all for you. And if you were to drive from the western half of the county into the eastern half, then the subscriber will "roam" to the East cell and you would continue to operate seamlessly.
So in addition to the collection of frequencies that make up a trunked site or simulcast cell, you also have "talkgroups" which are the virtual "channels" that the radios/subscriber operate on. As noted earlier, no one frequency is dedicated to any particular talkgroup, instead they just rotate around the pool of available channels in a first come/first serve manner. So one transmission on the Sheriff's Dispatch talkgroup of 27210 might take place on 454.475, and a few seconds later another transmission on the same talkgroup might take place on 453.425. The system tells all of the radios on that talkgroup which frequency to tune to, it all happens in the blink of an eye.
There's a lot more to it, but that should be enough of a primer to get you some basic understand. Oh and PS it's trunking, not "trucking".
