New Orange County EMS towers

[oc911emsandfire]

It seems as though Orange 911 keeps adding new towers to their EMS radio system (the old 718 channel) (not necessarily building them but adding the EMS operations channel) Their latest addition was the tower on Schunnemonk.

My big question is why do they still use such an archaic way to choose channels? Each unit in the field has to manually select a tower and then the dispatcher also has to pick a tower (or thats how I understood it worked).

To be honest, I'm more of a scanning enthusiast and have less knowledge about the actual radio system but how difficult would it be to just put in a voting system? Why have 5+ channels dedicated to talking on the same frequency to the same base?

 

[GTR8000]

EMS Paging/Ops has been licensed at Schunnemunk under WQFS593 since 2006.

Who is going to pay for the infrastructure to support voting and simulcasting? It's not as simple as you make it out to be.

Remember that a rather large geographic area across very varied terrain has to be covered. There's no way a single transmitter site can cover all of that area, which is why there are multiple sites. That can never be avoided.

Once you have multiple transmitters (or repeaters, in the case of the Ops channel), you're looking at a much more complicated system design if you want to use voting. Currently each site (repeater) has its own unique input PL using a shared frequency. If you changed that to a single input frequency/PL for every site, you'd wind up simultaneously keying every repeater in range of the mobile radio. That's no good. You'd need to either simulcast (which requires precise timing between sites and still has drawbacks), or you'd have to implement a somewhat complex system of talkback voting. The latter involves the system processing which site is receiving the strongest input signal, and transmitting it back over only that site's repeater. It's not foolproof, and it's not inexpensive to design and implement a system like that either.

So again, who is going to pay for all of it, especially in today's economy?

 

[radioman2001]

There was an extensive discussion on this some time ago, I believe the crux of the problem is they don't have the backhaul (phone lines VOIP etc) from their sites to do voting. As I understand it the dispatchers select the stations based on a PL code to the repeater. I had also recommended the voting in that discussion, but the problem with that is now you could have one unit transmitting across the entire county wasting valuable air time.

 

[GTR8000]

I had also recommended the voting in that discussion, but the problem with that is now you could have one unit transmitting across the entire county wasting valuable air time.

That's not really an issue, as you don't normally have OC911 transmitting on the same output frequency from different sites talking to different units simultaneously. Why? Because many of the sites have quite a bit of overlap, so you'd wind up with competing signals overlapping each other. Obviously you can have the situation now where mobile units are keying up at the same time, but you wind up with the same problem anyway given the output frequency/PL is the same among all sites.

 

[GTR8000]

As I understand it the dispatchers select the stations based on a PL code to the repeater.

Oh and just to confirm, this is correct. OC911 transmits on the input (control station) for the EMS Ops repeaters (same with the MRD and 911 Polling/Priority repeaters) using the same per-site input PL as the field units.

 

[APX8000]

Ok, time for my soapbox....

I suggested several things that could be done a long time ago to fix some of the problems. My first suggestion was going up on Schunnemunk. That took over 10 years from the time I suggested it to implementation!

My biggest problem (especially on the Police channels although it applies to EMS as well) is this...because the County transmits on the VHF repeater input vs. the VHF repeater output per site, there is no way for a unit in the field to transmit a priority message (talk over the dispatcher) in the event of an emergency.

A "remote base" method through a simplex RF link is how they should have set it up if they were going to use one frequency pair for all the site. The dispatcher could be in the middle of a message and still hear a unit calling him.

This would also help the dispatcher in knowing what site the field unit is calling in on. If each site is linked back and forth between the site and console by lets say different UHF simplex frequencies, only the site that the unit is transmitting on would light up at the console when he trips the remote base. When I dispatched at a local agency, we had it set up this way. The dispatcher talks back to the site on UHF as well, which trips the remote base to come off the repeater output on VHF. Units in the field would still be able to talk to each other through the repeater VHF pair as well.

i can't tell you how many times I've called in on the radio on one tower and was answered on a tower on the other side of the County. Or how many times on radio maintenance checks I'd hear "loud and clear on all towers" when I was calling on one.

Not very expensive in infrastructure vs. simucast systems using voting, frequency times, etc.

 

[KC2zZe]

(the old 718 channel)

Why have 5+ channels dedicated to talking on the same frequency to the same base?

Your count is a bit off. There are actually seven towers for use on 153.860R (77.0) - what is now correctly known as the Response channel. They are:

Arden
Beacon
Goshen
Graham
Heater Hill (in PA)
Mount Peter
Schunnemunk