700 MHz Overlays

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Russell

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How are the 700MHz overlays proposed for D/FW, Austin, San Antonio, and Houston supposed to work? My assumption is that existing or proposed P25 systems will use 700 MHz overlays as linking systems and that mobiles, will generally, not operate directly on the overlays within their own coverage areas, rather, they will stay on their own frequencies unless they move outside their coverage area.

In other words, a unit within his own coverage area, say Irving, will switch to an "Interop" channel and the overlay will carry that traffic to other systems in the region. Am I on or off base here? Say an Irving mobile wants to talk to Plano, the Irving unit will switch to an interop channel and the 700 MHz overlay will handle the link to Plano. This works fine until that Irving unit is chasing somebody into Plano and the Irving freqs will no longer be accessible. What happens to the mobile unit? Does he switch directly to the 700 Mhz overlay while chasing? This would seem the logical choice.

Is there a technical discussion of how these overlays are supposed to work?

Thanks,
Russell
 

texasemt13

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In other words, a unit within his own coverage area, say Irving, will switch to an "Interop" channel and the overlay will carry that traffic to other systems in the region.

This is how I understood it.

Say an Irving mobile wants to talk to Plano, the Irving unit will switch to an interop channel and the 700 MHz overlay will handle the link to Plano.

Again, my understanding.

Does he switch directly to the 700 Mhz overlay while chasing? This would seem the logical choice.

This would seem the logical (albeit, more expensive) option- and the most reliable.
 

W5TWX

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Very interesting and good questions. Wonder if we could get "Garyva" to chime in on this and tell us what he knows about this system or if he doesn't know anything.
 

SCPD

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some of these might be helpful

http://www.ntia.doc.gov/psic/IJ/tx.pdf
http://www.dfwinfo.com/cs/radio/pdf/HarrisCountyPresentation091307.pdf
http://www.nctcog.org/cs/radio/pdf/Region40_700MHz_ApplicationReview.pdf
Spectrum Home
http://www.nctcog.org/cs/radio/pdf/Region40_700MHzPlan.pdf
http://www.region49.org/PDF/TRCIP.pdf

Also, Its my understanding that, the Collin County tower system is to be used strictly for Serious incidents which require communications to Austin. Its not supposed to be used for an agency in chase from one county to another. Nor to be used for the day to day ops. The Collin 700 is off the Wilmeth tower. The Texoma COG is meeting on a Regional 700 MHz system but have no real expectation that it'll ever see daylight. Police Chiefs are reluctant to give up conventional towers and equipment for a "sharred" radio system. However, many of the origional concepts about 700 are being changed daily so who knows maybe we'll see a VHF agency flip to 700 while in pursuit. Some of the above documentation put "mobile gateways" in vehicles so there might not be a need to run several different radios in a patrol car.

Who knows - I'm watching this stuff like the rest of y'all so I don't know squat either.
 
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motorola_otaku

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How are the 700MHz overlays proposed for.. Houston supposed to work?
The 1A7 Borgnet P25 system will *eventually* completely replace the 2318 analog system, and function as the primary system for all of the existing 2318 users. There's even talk now of Houston city and the county sharing a zone controller when the CoH 700 P25 system goes online.

Personally, I expected 1A7 to completely replace 2318 sooner than it has so the County wouldn't have to reband 2318. But now there's rumors floating around that 2318 is going to reband in 1Q2010 sooooo... we'll see how that plays out.
 
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