How does it differ between agencies? Say, for example, police and animal control do not need to communicate with each other. How can each groups use frequency hopping without interfering with other departments/agencies
I am confused on our system in Iredell., The sysid is 1FC but theres a listing for nac of 1F0 for our trunking so hows that possible? I thought you can't have nac on a trunking system??
Thanks, for the video! I was wondering, though, how does the system know which users need to communicate with each other? For example, how does the system know that the sanitation workers need to talk to each other, versus the EMS workers needing to talk to each other? How does it let each user's radio know what frequency to use for the next transmission? And, what if a user in one department needs to talk to a user in another department? And, what if, for example. there are several sets of users in a particular group who need to maintain private communications (like two police officers working on the same case versus one police officer needing to communicate with the dispatcher? And, the frequencies in your example of a trunked system seem so different that it seems like they would need antennas tuned to operate on those different frequencies - because, one antenna is unlikely to have sufficient bandwidth to cover all of them efficiently, so, how do they address this issue in a trunked system?
He mentions this at 7:20. All radios register on the system upon power up, so the zone controller knows every radio by unit ID and it knows which talkgroup and which site each radio is on. At that point it is just a matter of the zone controller establishing the audio groups as needed and then tearing down those paths when the calls are completed. As for the antenna question, that is not an issue. There are antennas that cover the 700 and 800 bands. For lower land mobile radio frequencies like 150MHz or 400MHz, the commonly used LMR antennas have a much more narrow BW of 10MHz or less on most cases.
Oh and the frequency info is sent to the radios over the control channel. Bits are sent representing decomal numbers 0 to 4095 for FDMA and then the radios use a lookup table in the radio software to calculate the frequencies that the eadio needs to synthesize for each call.
