Cobb County's digital plans?

[AndrewC75]

Does anyone know with certainty what type of system we'll end up with once Cobb goes digital? Is it going to be a full P25 system with 9600bps control channel, or a mixed-mode system with 3600bps control channel and P25 modulation on some talkgroups? Will it possibly start as a mixed-mode system and migrate to full P25 after a period of time? What about encryption? I suspect there will probably be some encryption, say for MCS and Intel and maybe SWAT, but does anyone know, again with certainty, whether any dispatch or talkaround channels will be encrypted?

The reason I'm asking is because I'm trying to understand what it will take to keep the ScanCobb.com audio feeds online after the switch to digital, which is supposedly in the Spring. If I can get away with keeping the feed online with some digital-capable BC250D's, then it might actually be possible to keep the feed online.

 

[BANDIT]

Just a note for you. BC250D's will decode P25 digital audio but in conventional mode only.
They will not follow the 9600 control channel and track it. It will take the BC296D, BC796D, Pro96 or the Pro2096 to trunk and follow a 9600 control channel.

 

[AndrewC75]

That is correct, of course. Information I have received (that I'm waiting on permission repost in-full) is that Cobb is currently and will remain a 3600 baud system with APCO P25 common-air interface modulation available. At this time, no talkgroups are using the P25 option. So the BC250D will track it and demodulate it when talkgroups go digital. That being said, the BC250D may not be able to track the system after rebanding takes place. It'll take a BC296D or newer to better prepare for rebanding.

 

[b7spectra]

Word has it that there won't even be any testing until Spring 2006. Non-public service will be first up and if it works ok for them, then they will switch the rest over. I'm running Trunker right now and have not seen any digital signal come up yet.

 

[b7spectra]

Compliments of Andrew told me to monitor 859.2125 - 859.2125 is currently running a 9600 baud digital control channel! SY17D T0101 BEE00. No channels active at this time! Monitoring with my Pro-96. Unfortunately, my Trunker machine only has a 2 level data slicer on it.

 

[AndrewC75]

As this control channel is definitely local, and is on one of Cobb's licensed frequencies, we must assume that Cobb is migrating to a P25 system from their current analog system. They have already taken 859.2125 from the analog system and will probably take channels from the analog system as they start moving traffic to the new system. All Cobb montiors: Time to replace those analog scanners with APCO P25-capable ones!

 

[AndrewC75]

Compliments of Andrew told me to monitor 859.2125 - 859.2125 is currently running a 9600 baud digital control channel! SY17D T0101 BEE00. No channels active at this time! Monitoring with my Pro-96. Unfortunately, my Trunker machine only has a 2 level data slicer on it.

Mike,
What about Pro96com? Can't you do some Trunker-like monitoring with a Pro96 and that utility?

As of this posting, the site with the info on it is down, but it's: http://www.mvpcollaborative.com/p96/

 

[n4voxgill]

looks like your going to luck out with your 250D as the Cobb frequencies are not in the rebanding range.

 

[AndrewC75]

A BC250D won't track a 9600 baud system, so no, it won't work. And Cobb has numerous frequencies that will be affected by rebanding:

864.0625
866.0125
866.1625
866.5125
867.0125
867.1625
867.5125
868.2250
868.4500
868.9625
866.7000
868.2250
868.9625

 

[kikito]

Compliments of Andrew told me to monitor 859.2125 - 859.2125 is currently running a 9600 baud digital control channel! SY17D T0101 BEE00. No channels active at this time! Monitoring with my Pro-96. Unfortunately, my Trunker machine only has a 2 level data slicer on it.

You can always use Pro96Com with your Pro-96. No slicer or discriminator needed. You can find the latest version here: (you will need to join the group)

http://groups.yahoo.com/group/PRO96COM/files/

And if you do have a discriminator tap, you can also try UniTrunker: (no slicer needed either)

http://www.radioreference.com/wiki/index.php/UniTrunker

 

[BANDIT]

UniTrunker is great. The latest version was just released and working great for me. You can find the download link in the Yahoo Trunker groups. Does 9600 Dig, Motorola, Edacs and others. It takes a disc tap from the scanner to the soundcard mic in or line in. No slicer needed. Still waiting on control for the voice sacnner. Try it out.

 

[b7spectra]

Running Pro96Com right now, it's picking up the system perfectly. No talk groups, at this time, but it is showing SYS 17D T0101 BEE00. Channels are 856-9.2125. I'm going to leave this run all day while at work and see if anything pops up!

 

[4phun]

Running Pro96Com right now, it's picking up the system perfectly. No talk groups, at this time, but it is showing SYS 17D T0101 BEE00. Channels are 856-9.2125. I'm going to leave this run all day while at work and see if anything pops up!

I get the same information, naturally, at my house with a 99% signal off that tower. Not bad for living in a hole! I am leaving the PRO-96 on to montior this continously from now on. Don't forget to set the bank to TRUNK MO.

Anyone using a BCD396T on this channel?

 

[BANDIT]

I have been monitoring it since last night with a Pro2096 and Pro96com on a laptop. Have not seen any group or radio ids yet. Seems to be running low power at this time. Forsyth County did the same thing when they first truned on their 9600 P25 system. Then when it went live it jumped up to 20db over S9 on the R8500 receiver.

 

[AndrewC75]

(crossposting to ScanCobb.com and ScanAtlanta Yahoo! Group)
Executive Summary: Cobb's digital system is already online for testing, the first users will appear within the next month or two, and it will be a year or more before most or all users are migrated to the new system.

First a disclaimer that I have every reason to beleive that this information is accurate, but plans change, governments are inefficient, and my sources could be ill-informed. Nevertheless, thanks to some background information received offline and some experimentation by Mike and others, here's the info I've gathered so far about Cobb's digital system. The system is already online, operating on frequencies previously occupied by channels of the analog system:

SysID: 17D
856.2125
857.2125
858.2125
859.2125: Control Channel
(I was initially told there are 5 digital channels, but the CC data doesn't lie)

I don't know the current output power of the system, or on which site(s) it's running. For some undetermined time to come (probably nearly a year or more) Cobb will run both systems side by side. Right now, the analog system bears all of the traffic, and therefore has a majority of the allocated frequencies. As services are migrated to the digital system, frequencies will be re-allocated to the digital system. Right now the system is up for testing only, however one or more non-essential county services will begin using the digital system in the next month or so. Public safety migration may begin around or after mid-year, and continue as the SPLOST money buys the radios. In the end, Cobb should be running a 26 channel APCO P25 system, and the analog system will be disassembled after arrangements are made to communicate with neighboring agencies that can communicate to Cobb agencies today via the analog system (Fulton, Atlanta, Douglasville, etc).

A final note on rebanding: It will probably occur smack in the middle of the analog to digital migration, no doubt wreaking havoc on everything. it could have a major impact on timing and certainly the frequencies on which the system runs. Hopefully the migration plans have been made with rebanding in-mind and will not be substantially altered

Conclusion: If you montor Cobb public safety and want to continue doing so, it'd be best to have your P25-capable scanner no later than mid-year. My BCD396T will be in my hands by the end of this month!

Enjoy!

 

[ButchGone]

Re:

This same kind of thing happened on the Chattanooga/Hamilton County TN system. The shop operated the new system control channel on an "unused" freq from the old analog system, then added four more freqs for voice traffic. As that new system got loaded down, they added additional repeaters into the system, until all that was left on the "old"system was five freqs, and then did the final switch over for remaining agencies.
There were just a handful of agencies on the new system to begin with, and as more freqs were added to the new system, more agencies switched over. During the process however, the "new" system would sometimes get busy because there were not enough freqs to handle the new load. The shop actually took a couple agencies off the new system and put them on the old system because of so many "busy signals." Based on what happened here, I would say you should start hearing traffic on the new system fairly shortly. At least techs working on the system. I wonder, if the Cobb system will be a 9600 system if it will be "interoperable" with other state/outside agencies that may be 3600?
One thing for sure, the "old" analog non-trunk technology was always "interoperable" because any manufacturer's equipment would work on anybody else's system as long as the freqs/squelch codes were programmed in. Oh well, everything is much more complicated now and gov't is having to spend mega millions just to be able to do what was done years ago...talk to the guys in the county next door. Happy New Year!

 

[kikito]

I wonder, if the Cobb system will be a 9600 system if it will be "interoperable" with other state/outside agencies that may be 3600?

Yes, it should be even more "interoperable" and backwards-compatible than before....

 

[AndrewC75]

That's one thing about a 9600 system... It's not backwards compatible. You can not have analog talkgroups on a 9600 system. That's what they have to figure out. My guess? They'll keep the analog system up with just a few channels for as many years as it takes for Fulton, Atlanta, St. of GA, and Douglasville to to digital. They should be able to cross-patch the analog system into the digital one for those channels.

 

[kikito]

That's one thing about a 9600 system... It's not backwards compatible. You can not have analog talkgroups on a 9600 system. That's what they have to figure out. My guess? They'll keep the analog system up with just a few channels for as many years as it takes for Fulton, Atlanta, St. of GA, and Douglasville to to digital. They should be able to cross-patch the analog system into the digital one for those channels.

You're right about no analog talkgroups are possible. They'll also have to upgrade their infrastructure, upgrade radios, if not get new ones in some cases, etc. That is not what I had in mind when I said backwards compatible.

It is backwards-compatible in the sense that now it'll accept a lot more external or legacy inputs from other types of transmissions or systems, either like you mentioned through soft and hard-patches, special interfaces, etc. I also meant backwards compatible in the sense that new radios for the 9600 systems (depending which ones they get) will be able to transmit in analog and digital, regular and narrow-band and if they get the options, even multiple-bands directly. So maybe I should've said it's going to be more versatile instead of backwards compatible.

The 9600 system in our area was tested during exercises and was succesfully letting people in the Airband, the Marine band and VHF-Hi all talk with each other with no problems. That's what I meant about compatibility, more provisions for inter-operability. Of course, there's some that'll argue that analog FM is already interoperable