In Vehicle Repeaters

[newtoscanning]

A question as to how they work. I understand in principal (referring to BMR) that the ambulance/cruiser/etc. will have a smartzone radio (VHF) in it, connected to a simplex radio (UHF). When an officer/medic keys up their portable the radio transmits on a simplex frequency into the radio into the car, then it in turn keys up the trunked radio, and repeats it into the system; hence the vast spread of transmitting sites. I also understand that the actual repeaters are probably not two radios linked more so just one with dual function.

The part that I don't understand is if two (or more) units (regardless if EMS/Police/Fire) attend a call, how do they keep all of the repeaters from all trying to key up and repeat the voice into the trunk system; obvious answer, all the portable's have different frequencies. However there are how many OPP units, how many different ambulances/response cars, how many fire trucks, it would be a logistical nightmare trying to co-ordinate that (from a programming/frequency allocation perspective).

The only conclusion I can come to is that the radio has a frequency bank, and it will auto-negotiate with radios in the area (only a 1/2-1 mile range) to ensure everyone is on a different simplex frequency.

Any ideas?

Thanks

 

[mdulrich]

Read the following link, it will answer, at least, some of your questions.

http://www.pyramidcomm.com/svr200.html

Mike

 

[slypx]

Mobile repeater

And here :

http://www.vsp.state.va.us/downloads/STARSContract/Appendix 05 - 08a - Futurecom Mobexcom.pdf

Among other places, this Futurecom products is use by the Ontario Provincial Police (OPP) and the Sûreté du Québec (QPP), two of the largest police department in Canada with booth over 5500 sworn police officers.

This new numeric repeater has some "intelligence" in it and will only allow one repeater to be "ON" on the same channel in the same area to avoid cross-channel interference.

 

[imcleish]

Newtoscanning,

Great question, and in reality this was a MAJOR hurdle in the implementation of the fleetnet system, I recall this issue from initial testing in the Cambridge and London CACC arears of Zone 1.

I can only guess, this is one of the reasons the radio/repeater system per vehicle is so costly.

Others have provided the technical information, but essentially, through technology, only one repeater per UHF frequency will key up for all the portables on said frequency in a given area.