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SRRCS/ComLink Question

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scannerboy02

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I was noticing today during a ComLink between SD 1<-->SP 1<-->CHP BUL VAL that SD 1 and SP 1 were on two different voice channels on both SRRCS sites, a total of four frequencies. That got me thinking that in the event of a major emergency when several TG's on the SRRCS were ComLinked it could add up to a lot of system frequencies being used to broadcast the same traffic.

During a major emergency the system could already be taxed with voice channel requests from all the other TG's that would be in use during said major emergency and then to have all the ComLinked TG's (some being priority users) make a voice channel request at the exact same time could cause a big problem.

Anyone know if the SRRCS has a way to know what system TG's are in a ComLink and if it would have the ability to put all those TG's on the same voice channel on each site thus only using a total of 2 system frequencies?

Or they could all just go to one TG. Like that's going to happen during an emergency... it could ;-)~
 

scannerboy02

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so you could listen to either sac pd sac so or chp blu and here the same thing?
That's how it worked today.

The ComLink is used so that everyone involved can hear each other by connecting the radio systems together over the ComLink.

Basically the dispatch center for each agency adds a channel to the ComLink and everyone will hear the same thing on all the channels.
 

clanusb

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on a totally different side note....many wonder why fire still has VHF abilities....thats the main reason right there..as a back up. if and when the 800 system goes down, Fire will still be able to operate somewhat on the VHF freqs.

does PD and SO still have some of their old 400 freqs or is everything 800 for them?
 

gmclam

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Sacramento TRS

On a normal day, the main channels are repeated on both the city and county sites. So you may have a county transmission on let's say 821.1375, and it is repeated on 866.1375; but that same transmission may also be on 866.2500 on the city side. I expect it will also be on 821.2500.

Now let's say the ComLink is between Sac PD1 and SSD 1. So then you end up with the following:
City site
Sac PD1 821.2500 -> 866.2500
SSD 1 821.4000 -> 866.400

County site
Sac PD1 821.3500 -> 866.3500
SSD 1 821.1375 -> 866.1375

In other words, it did not increase the channel usage on the system from 1 to 2, it went from 2 to 4 because main channels are already cross broadcast.
 

scannerboy02

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Correct, and every time you add a SRRCS user to the ComLink you up the number of used system channels by two.

Add EGPD 1 you now have 6 channels used
City site
Sac PD1 821.2500 -> 866.2500
SSD 1 821.4000 -> 866.400
EGPD 1 821.5875 -> 866.5875
County site
Sac PD1 821.3500 -> 866.3500
SSD 1 821.1375 -> 866.1375
EGPD 1 821.4375 -> 866.4375

Add FPD 1 you now have 8 channels used
City site
Sac PD1 821.2500 -> 866.2500
SSD 1 821.4000 -> 866.400
EGPD 1 821.5875 -> 866.5875
FPD 1 821.7750 -> 866.7750
County site
Sac PD1 821.3500 -> 866.3500
SSD 1 821.1375 -> 866.1375
EGPD 1 821.4375 -> 866.4375
FPD 1 821.7125 -> 866.7125

and so on.

I am saying if some how the system had a way to put all ComLinked SRRCS users on the same channel per site

Something like this using only 2 channels
City site
Sac PD1 821.2500 -> 866.2500
SSD 1 821.2500 -> 866.2500
EGPD 1 821.2500 -> 866.2500
FPD 1 821.2500 -> 866.2500
County site
Sac PD1 821.3500 -> 866.3500
SSD 1 821.3500 -> 866.3500
EGPD 1 821.3500 -> 866.3500
FPD 1 821.3500 -> 866.3500

it would make a big difference in the amount of used system channels and make those other channels available for other system users, especially important during a major emergency.

Question, would doing a patch of all the SRRCS users on a dispatch console and then adding that patch to the ComLink do what I am saying or are all the patched users still on separate system channels? And is patching SPD/SSD/EGPD/FPD and so on even doable by one dispatch center?


Or just have them all change to one TG.


See how much easier and cheaper (but yes.. less fun) changing a channel is, and if I remember correctly was the big selling point of the 800MHz system in the first place ;-)
 

RolnCode3

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I don't see the real problem. You're talking about the most used talkgroups with the highest priority on the entire system. So they're using resources anyways.

Patch w/ multiselect would put everyone together, right? But then CHP is not included. If I remember, the commlink can't be patched (though I'm not an expert). So that would be either patch only srrcs tg's together, or commlink and allow non-srrcs to participate.

Also, commlink allows agencies to join and leave on their own. Patch/multiselect can remove control from the agency depending how it's done. If the experts see this they could confirm/correct any misinfo.
 
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K6CDO

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on a totally different side note....many wonder why fire still has VHF abilities....thats the main reason right there..as a back up. if and when the 800 system goes down, Fire will still be able to operate somewhat on the VHF freqs.
The reason fire still has VHF (High band) is California's Fire Mutual Aid system is based around everyone having VHF High Band. This permits any rig / crew that would be involved in an incident anywhere in the state to be able to communicate. The VHF High band infrastructure available in the fire Comm Centers supports out of area mutual aid comms, and allows for back-up comms in case of a system failure, and helps the fire agencies meet industry standards for redundant dispatch capabilities [this helps keep fire insurance rates down].

does PD and SO still have some of their old 400 freqs or is everything 800 for them?
The last I saw all LE is on 800.
 

dougr1252

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A frequency and a channel are two different things:

866.2500 = frequency
821.2500 + 866.2500 = channel

In a trunked system, every channel is a repeater, so every channel is implemented by a frequency pair. Even if 866.2500 is active by itself when a dispatcher is transmitting via direct link to the transmit site, 821.2500 is not usable by anybody else at that moment unless they're interrupting. Putting the same traffic on two different TGs in a system, using 2 channels, seems wasteful but they probably have to based on the limited channel sets in each radio. And all that still equals only one communications path since only one user can transmit at a time.


Correct, and every time you add a SRRCS user to the ComLink you up the number of used system channels by two.

Add EGPD 1 you now have 6 channels used
City site
Sac PD1 821.2500 -> 866.2500
SSD 1 821.4000 -> 866.400
EGPD 1 821.5875 -> 866.5875
County site
Sac PD1 821.3500 -> 866.3500
SSD 1 821.1375 -> 866.1375
EGPD 1 821.4375 -> 866.4375

Add FPD 1 you now have 8 channels used
City site
Sac PD1 821.2500 -> 866.2500
SSD 1 821.4000 -> 866.400
EGPD 1 821.5875 -> 866.5875
FPD 1 821.7750 -> 866.7750
County site
Sac PD1 821.3500 -> 866.3500
SSD 1 821.1375 -> 866.1375
EGPD 1 821.4375 -> 866.4375
FPD 1 821.7125 -> 866.7125
 

inigo88

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I'm not familiar with the SRRCS comm link, but I don't understand why they don't create an extra "CHP" talkgroup with the lowband patch radio affiliated to it.

Then they could take this CHP talkgroup, along with everything else, and multi-select them all together into one supergroup that would only use one voice channel per system.

Maybe I'm missing something?

Inigo
 

ssd

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Well for 1 chp now is geting the efj 5100 800/700 p25 radios so no need to make a chp talkgrupe.
 

WayneH

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Putting the same traffic on two different TGs in a system, using 2 channels, seems wasteful but they probably have to based on the limited channel sets in each radio. And all that still equals only one communications path since only one user can transmit at a time.
You're correct and whomever was in control of this "mickey mouse" setup should get a talking to. To make efficient use of channels when patching the control channel uses data command words to tie (or patch) talkgroups together which causes two or more talkgroups to trunk out to the same voice channel. The TGs should have been patched together via a console so this method was used.


Some history and technical info:
A very long time ago the method you described was used (City of San Diego is an example) but that was done to support non-SmartNet radios. In order for a radio to understand the patch and MultiSelect control channel commands it must have a SmartNet or SmartZone feature package. But of course this was previous to these plug in your radios and they're patched, viola! method.

When dealing with a trunked system the concept of trunking removes fixed channels/frequencies since all patching (outside of a physical site) is done with just an audio path. SmartZone systems have switches, similar to a telephone switch, that are designed just to route audio to other sites, consoles, voice recorders and externally attached devices for hard patching to other systems or conventional channels.
 
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avtarsingh

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63920 F9B Analog CHPLNK Patch for CHP Interop

chp tg has been on the system for almost 2 years now

should have 3 - blue gold and black easy to patch
 

RolnCode3

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63920 F9B Analog CHPLNK Patch for CHP Interop

chp tg has been on the system for almost 2 years now

should have 3 - blue gold and black easy to patch
lot longer than 2 years. It existed on the 4328 system as well. Don't know how it's supposed to be used, but I'm not aware of a single instance where it was used.

I'm curious how you guys are coming to all these conclusions about the number of frequencies being used? Were you running multiple unitrunker instances? A whole bunch of scanners that happened to stop on different frequencies? Not criticizing, but curious if there's another explanation for whatever you observed that led to your conclusion.
 
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scannerboy02

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You're correct and whomever was in control of this "mickey mouse" setup should get a talking to. To make efficient use of channels when patching the control channel uses data command words to tie (or patch) talkgroups together which causes two or more talkgroups to trunk out to the same voice channel. The TGs should have been patched together via a console so this method was used.
So if I understand this correctly if lets say the Sac Sheriff Comm Center was to MultiSelect lets say SD 1, SP 1, EGDP 1 and FPD 1 it would put all radio traffic from all radios on any of those TG's on a single voice channel? and do that on both sites?

If so is it possible, as RolnCode3 asked, to add that MultiSelect group to the ComLink?


I'm curious how you guys are coming to all these conclusions about the number of frequencies being used? Were you running multiple unitrunker instances? A whole bunch of scanners that happened to stop on different frequencies? Not criticizing, but curious if there's another explanation for whatever you observed that led to your conclusion.
I run 8 trunked radios in my office and when the ComLink started I put one radio on each involved TG on each site and could see on the display that they were all on different voice channels.

I had noticed this during some ComLink testing a while back but was not able to confirm it with the above method until the incident Friday.
 

WayneH

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So if I understand this correctly if lets say the Sac Sheriff Comm Center was to MultiSelect lets say SD 1, SP 1, EGDP 1 and FPD 1 it would put all radio traffic from all radios on any of those TG's on a single voice channel? and do that on both sites?
One of those talkgroups becomes a "SuperGroup" and accompanying commands are sent out over the control channel to all radios monitoring those talkgroups to watch for the SuperGroup. So, yes and yes.

If so is it possible, as RolnCode3 asked, to add that MultiSelect group to the ComLink?
It sounds like to me this ComLink is just a standard cross-connect box that allows you to plug in multiple radios and route the audio (or transmit TO) any one of them. If that is the case it is independent of the system administration and cannot operate how a dispatch console would do it. Only a dispatch console on the system can patch or MultiSelect multiple talkgroups systemwide.

My guess is whomever was in charge of this setup didn't want to bother dispatch to get things setup. When dealing with interoperability this is a poor frame of mind. It's nice they know how to use their ComLink but a patch through dispatch would have been more reliable (and efficient).
 
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scannerboy02

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From what I understand about the ComLink, it works through a microwave network and several dispatch centers in Sacramento, Placer and Yolo (possibly others) county's can select a channel on its own radio system then add that channel to the ComLink and all radios on the selected channels will hear all ComLinked radio traffic.

So for example CHP can add a channel, Sac Sheriff can add a channel, Folsom PD can add a channel, Galt PD can add a channel, Roseville PD can add a channel, Yolo Sheriff can add a channel, Davis PD can add a channel, and so on and they all will be able to talk to each other through the ComLink.
 

inigo88

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I agree with Wayne. I cannot see a legitimate reason to use 8 voice channels when 2 would do. Given the amount of non-public safety users on SRRCS to begin with (garbage trucks, trains, buses!), voice channels are a hot commodity. Frankly, I'm horrified they're being so blatantly wasted with this system.

My county has multiple local law enforcement and fire agencies each with their own comm centers, and this does not stop them from all being able to incorporate multi-select patching. Whichever talkgroup that belongs to the console that initiates the multi-select becomes the SuperGroup.

The infrastructure needs inside and outside the trunking system are different! Sure there will be a hodgepodge of microwave and audio paths connecting outside agencies to the system, but that all has to be funneled down into a dispatch console, with the dispatcher acting as the flood-gates and allowing outside agency channels onto the system through console radio IDs (correct me if I'm wrong). This would likely be at the main county comm center, which would be SSD I'm assuming? Within the system, all the talkgroups can be easily multi-selected onto one supergroup. But since the audio from these outside agencies are coming through console radio IDs into the system (radios that are cross-band repeating traffic in and out of the system), they too can be affiliated to the same supergroup, or in a simplified case - affiliated to some generic mutual aid talkgroup which is then multi-selected in with everyone else.

I'm not sure of the multi-select talkgroup limit (Wayne would know!) but if it were exceeded, that is what mutual aid talkgroups and channel knobs were invented for. Train the participating agencies to be able to switch to it and affiliate the outside agency audio via the console to it.

In either case, you're still only using one voice channel per system.

Since I have no way of verifying this I can only go off of what scannerboy has said. Granted 23 City and 21 County are a lot of voice channels, but it's still no excuse to tie up 8 channels with the exact same audio. Worst case scenario in a very large scale emergency where everyone is trying to talk at once, that could be 6 "11-99s" or firefighter down calls. Why FURTHER limit your ability to communicate when the nature of trunking already limits the ability of its users to get through in a period of demand?

I count 560 talkgroups and 44 voice channels between both systems. That means 7% of the total system talkgroups could be in use at any time. Why further lower those odds?

[/Rant] :)
 

Sac916

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I started reading this thread - then my eyes started hurting.... too many words.

I can tell you this for a fact.

We have CommLink'd nearly every user at once several times without a problem. Several times a month a few ( 5 or so ) users will do a CommLink test. There are monthly quotas to meet.

When "we" CommLink, we Multi-Select and Patch to the CommLink module/talkgroup.
For SRRCS users it's very simple, but CHP often has difficulty completing the task.

The CommLink is a separate piece of equipment and not part of the SRRCS Network.
( Don't ask me about specifics, I don't know )

SSD does not use or have equipment for the old 400 freqs - but SSD does have access to conventional freqs in case there is a total SRRCS radio failure.
 

Sac916

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So for example CHP can add a channel, Sac Sheriff can add a channel, Folsom PD can add a channel, Galt PD can add a channel, Roseville PD can add a channel, Yolo Sheriff can add a channel, Davis PD can add a channel, and so on and they all will be able to talk to each other through the ComLink.
Yup - Simply patch and multi-select any talk group to the "CommLink" talk group. Done.
This allows any agency to jump in and out without being locked-down on a patch. The issue with simply patching is the console that initiates the patch must disconnect the patch. So if SPD patches to SSD, SPD must unpatch.
 
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