Simulcast and IR sites
"The only thing that seems odd to me is that all of the towers are shown to have the exact same freqs. Can a trunked system be set up this way or could this be something conventional?"
Many trunked systems have multiple tower sites that transmit the same information at the same time....this is called simulcast. In this manner, a county system could provide improved coverage with a limited number of channels. When a system user transmits into the system, his traffic is repeated on all of the tower sites and ultimately the same frequency at all of the sites.
Conversely, you have the Palmetto 800 system which has Intelli-repeater sites (as well as some simulcast). They act as mini-trunked systems at each of the tower sites. For example...Augusta has, I think, 5 sites to cover Augusta-Richmond County. Each site has its own control channel separate from the other sites. Based on affiliation to a site, when a user transmits he may key up one site or may keep up all five sites. Let me describe affiliation...
I turn on my radio and it talks to the system via the control channel telling the system my radio ID and the talk group that I want to be associated with. Based on system parameters and if my radio is valid, traffic will be passed to me on my talk group by what should be the closest tower site. Let me bring this together...
If you were near site 1 and I am near site 2 on the same talk group, we would use two different channels (one at each site to pass the traffic) in the intelli-repeater world. Towers 3,4, and 5 don't transmit. Officer Friendly turns on his radio on our talk group near site 3 and now our traffic is routed to his radio by yet another channel at site 3.
In a simulcast world, you are at site 1, me at site 2, officer friendly at site 3 and all of us are using the same channel at each of the sites inlcuding sites 4 and 5 even though no one is near affiliated to those sites.
I hope that this helps!
