What about a system with multiple repeaters on the same frequency ? How would that essentially be set-up ? I'd like to hear from the pro's like ff026 and SCANdal...
I've argued with my county over this for many years, especially on our EMS channel. I'm referring to the Orange County, NY 718 frequency.
In order to increase coverage in the county, they basically put up more repeaters. The output frequency of the repeater is 153.860 using PL 77.0.
The county has 5 different sites where the actual repeaters are located:
Beacon, Arden, Graham, West Point and Mt Peter.
The input frequency to the repeater located at each site is the same. The input PL however, is different so you only key the repeater you want. This works fine in some instances, but bad on others. Here is why...
I've called the county on one tower and they answer me on another. Fine if I'm in hearing distance of that other tower, such as when mobile, but on portable forget it...sometimes they answer on the tower located on the other side of the entire county. Needless to say on a portable they sound weak and low even though I sound 5X5 to them. I've also called on a radio check and they respond "loud and clear on all towers" when I'm only transmitting over one tower.
Reason being is their system is set up just like my radio, they have to select the repeater to talk on and all the receivers at the console are actually the repeater output instead of input (opposite of what NYPD, FDNY does), which is the same for all five towers ! So all lights will blink on the console for all towers instead of the one I'm calling on. Additionaly, if they are talking, field units cannot transmit, because they don't hear the repeater input. They hear it over the repeater output. When talking, it mutes the repeater input because they are using it to transmit to the repeater site and overrides mobiles and portables because of more watts and a better antenna. Poor design, poor set-up. No tie-line to the repeater such as T1 or microwave to key it from the dispatcher center, just 5 radios basically set up to talk on five different repeaters by using five different input PLs.
So how do you fix the problem? Could you change the console to listen to the repeater input instead of the output. This woudl have to be done to listen from the actual repeater site and not the center. Then use links from the sites to the center, whether it be microwave or UHF, etc? I'm guessing you would have to link it the opposite way to key the repeater site from the center as well.
What about a voted system with multiple repeaters?...would one be required at each site? I'm guessing no if you change the repeater input of all five towers to use the same input PL. This would put access to all repeaters over one channel. You have all five sites send the signal to the voter, which receives the best one and sends it to the best repeater and the console at the same time. Where do you locate the voter? How do you send that signal back to the repeater site as well as the console?
The dispatcher could then select the actual tower site that they are hearing the signal on and talk back to the unit in the field on the repeater output instead of input. But if all the towers are on the same frequency and PL, how do you tell which tower the signal is coming from ?
We want to eliminate field units from having to change channels when driving all over the county to be within tx range of the best tower. Just one channel to access all. And we want to elimate the dispatcher guessing the right tower.
How about a little help explaining how it's done for us novices? And what about a simulcast system so the best received signal gets transmitted over all the towers so someone on portable on one side of the county can talk to someone on portable on another side. The voted system without simucast could not accomplish that correct ?