CHP 700 MHz Extenders

[KMA367]

2. If the VRS can be tied to various channels on the fly, then there might be more problems with this scheme than I thought initially. If you have an incident with 3 CHP officers at a scene with VRS, and 1 wants to talk thru his mobile on lowband, 1 wants to talk thru his mobile on highband, and 1 wants to talk thru his mobile on UHF, then what VRS channels will be used? There are only 2 VRS channels allocated per radio zone. I dont think anyone wants any 1 VRS channel to be carrying traffic from two different channels at VHF or UHF or wherever.

Per the list of allocated VRS channels (posted earlier in this thread), any incident will be at most able to support 2 VRS at the same time.

"Pre"PS: Will the officers not be able to access all bands from their car radios? If there are only two VRS channels available at a scene and they're both in use, I should think the car radios would still be available if they need that much interoperabiity.

At the CHP as in life itself, you can only anticipate, plan, design, and pay for a finite number and severity of eventualities. There come times when you simply don't have enough people, equipment or other resources to meet the immediate demand, and it results in anything from minor inconveniences to fatalities. I've "been there, done that" as a dispatcher and disp supervisor, and while you never get used to it, you either learn to accept the inevitability of it or else find a different job. System designers and users have (or always should have) those limitations in mind, and do the best job they can with what they have to work with.

If they provide for three VHS channels, one day they will wish they had four. With four they may need six. "If wishes were horses..."

 

[inigo88]

Remember too that there was only ONE VHF extender frequency for all the mobile extenders in the entire state (well except for Redding or something, which had its own). They made it work. There was an ingeniously simple priority system built into the extenders - which we discussed at length in this forum a while back - which allowed multiple cover units arriving at scene to use only one extender.

It worked by playing a high pitch tone each time a new unit arrived on scene and turned on the extender, which told all the other extenders it was taking over and to turn themselves off. The catch was if officers drove around with their extender left on by accident it wouldn't work properly and the system would have to be cycled manually.

I suspect a similar system is built into the VRS extenders (hopefully a smarter one). If an officer needs to access a secondary car radio like the VHF or UHF while the primary lowband is already in use, I'm sure they could do so via the secondary VRS channel assigned to that division. Don't expect the system to solve all problems, but it seems like a step in the right direction from the original 154.905 extender (excluding the digital->analog audio quality issue).

As for your question on lowband simulcast: "Simulcast" is not the right word.
What they actually do (and correct me if I'm wrong), is what they've always done -- Receiver voting, which chooses the closest Tx site for the dispatcher to respond on. They then pick the most centralized Tx site for the given area and repeat the mobile frequency through that. So for example, you may be driving on the outskirts of the coverage area for that channel, and hear the officers coming in scratchy (because the mobile repeat tower is far away). But if an officer pulls you over and calls in your 10-28, the dispatcher gets their transmission through the voter, which routes their reply through the closest Tx site (either automatically or manually selecting it) and you hear them crystal clear. So it's not true simulcast since only one tower is transmitting at a time.

 

[jlanfn]

I wasn't going to post this for fear of taking the thread off topic, but since several people have mentioned it:

CHP uses simulcast on the lowband primary channels of:

• Channels dispatched by Los Angeles Communications Center.
• Some channels dispatched by Golden Gate Communications Center. (I believe they are still in the process of moving the whole division to simulcast.)
• Channels dispatched by Inland Communications Center.
• Channels dispatched by Border Communications Center.

All lowband channels not dispatched by one of these communications centers use non-simulcast vote steer.

 

[inigo88]

Doh! Thanks for the correction. Sadly I've lived in two of those divisions that simulcast, but I forgot that was the case.

 

[officer_415]

2. If the VRS can be tied to various channels on the fly, then there might be more problems with this scheme than I thought initially. If you have an incident with 3 CHP officers at a scene with VRS, and 1 wants to talk thru his mobile on lowband, 1 wants to talk thru his mobile on highband, and 1 wants to talk thru his mobile on UHF, then what VRS channels will be used? There are only 2 VRS channels allocated per radio zone. I dont think anyone wants any 1 VRS channel to be carrying traffic from two different channels at VHF or UHF or wherever.

I still don't think you understand how the VRS system works. All units use one 700 MHz frequency (their primary) to access their various channels:

CHP Officer 1 using 700 MHz portable on VRS 1, NAC 1 >>> mobile radio 1 >>> low band channel

CHP Officer 2 using 700 MHz portable on VRS 1, NAC 2 >>> mobile radio 2 >>> high band channel

CHP Officer 3 using 700 MHz portable on VRS 1, NAC 3 >>> mobile radio 3 >>> UHF channel

A single VRS unit can support traffic on several low band / high band / UHF channels. Transmissions cannot occur simultaneously, but CHP officers usually stay on their primary dispatch anyway. The VRS simply gives them the ability to communicate with allied agencies when necessary.

Like Inigo said, the 700 MHz extenders are a huge improvement over the old extenders, which could only operate on whatever low band channel the car radio was set to. The new extenders allow each officer to use all of his mobile radios on foot. And while they don't allow 3 separate officers to have conversations on 3 different channels all at the same time, usually the need for coordination means that all CHP officers at the scene will be operating on the same channel.

 

[bcorbin]

Ok, I'll bite... How does the radio in Officer 1's car (listening on VRS1) know it's not being steered to the high-band channel when Officer 2 transmits on VRS1 with NAC 2?

I think you need a separate VRS for each link.

If Officer 2's radio doesn't steer Officer 1's car to high-band, there's a high probability that simultaneous traffic on the two bands will cause a double on VRS1 that kills reception on both portables (remember, a) it's an incident large enough to require links on three bands and b) digital doesn't handle doubling well).

I still don't think you understand how the VRS system works. All units use one 700 MHz frequency (their primary) to access their various channels:

CHP Officer 1 using 700 MHz portable on VRS 1, NAC 1 >>> mobile radio 1 >>> low band channel

CHP Officer 2 using 700 MHz portable on VRS 1, NAC 2 >>> mobile radio 2 >>> high band channel

CHP Officer 3 using 700 MHz portable on VRS 1, NAC 3 >>> mobile radio 3 >>> UHF channel

A single VRS unit can support traffic on several low band / high band / UHF channels. Transmissions cannot occur simultaneously, but CHP officers usually stay on their primary dispatch anyway. The VRS simply gives them the ability to communicate with allied agencies when necessary.

Like Inigo said, the 700 MHz extenders are a huge improvement over the old extenders, which could only operate on whatever low band channel the car radio was set to. The new extenders allow each officer to use all of his mobile radios on foot. And while they don't allow 3 separate officers to have conversations on 3 different channels all at the same time, usually the need for coordination means that all CHP officers at the scene will be operating on the same channel.

 

[officer_415]

Ok, I'll bite... How does the radio in Officer 1's car (listening on VRS1) know it's not being steered to the high-band channel when Officer 2 transmits on VRS1 with NAC 2?

I think you need a separate VRS for each link.

If Officer 2's radio doesn't steer Officer 1's car to high-band, there's a high probability that simultaneous traffic on the two bands will cause a double on VRS1 that kills reception on both portables (remember, a) it's an incident large enough to require links on three bands and b) digital doesn't handle doubling well).

Because the extenders have a built-in priority structure which ensures that only one VRS is active at any given scene. As Inigo described, the old extenders accomplish this by sending out a tone which basically shuts down all exenders except the last car to arrive on scene. The 700 MHz extenders have an improved system that determines priority during repeater idle time, without user intervention.

In the scenario I described above, mobile radios 1-3 are all in the same patrol car. All of the officers would use the same VRS for their communications on different bands. Yes, this means that they can't transmit simultaneously on multiple channels, but all CHP officers at a scene will usually be on the same channel anyway.

 

[bcorbin]

So - portable units affiliate with the mobile that has taken precedence at the incident and the mobile stores a map of RID's vs NAC's so that it knows when/if it's being steered to another frequency? That seems doable, and it would solve the steering problem.

I would still be a bit concerned about the fact that Officer 2 may not know he didn't receive a transmission on high-band because the mobile was tied-up with low-band traffic.

Although I suppose (maybe not in phase 1?) that high-band and low-band could be multiplexed and streamed to both radios... that would be kind of neat...

 

[zerg901]

mlangeveld - I really think your trying to put lipstick on a Palin. But I have to admit I have not put a lot of thought into your recent comments yet.

I think that the system will work like this. If CHP Car 1 chases someone into a neighborhood, then CHP Officer 1 will chase the suspect with his portable on VRS1 which will be connected to CHP Channel 1. CHP Officer 2 who arrives in CHP Car 2 will set his portable to VRS 2 and set his mobile radio to the local police agency channel. Any subsequent CHP officers who arrive at the scene can chose either VRS1 or VRS 2. I would imagine that the safest scenario would pair up CHP officers - one on VRS 1 and one on VRS 2.

Of course it would probably be nice to scan a few CLEMARS and other local PD channels (maybe even a local PD tac channel), but I dont see how that can be accomplished if CHP just has 2 VRS channels allocated by radio zone.

The comments about "priority features" dont ring totally correct to me. I cant imagine that anyone wants a system where you can only monitor 1 and half channels.

Lets diagram the scenario I described above.

CHP Portable # 1 >>>> VRS Channel 1 >>>>> MO3 #1 >>>> CHP Channel 1

CHP Portable # 2 >>>>> VRS Channel 2 >>>>> MO3 #2 >>>>> Local PD channel

on the flip flop

CHP Channel 1 >>>>> MO3 #1 >>> VRS Channel 1 >>> CHP portables (multiple)

Local PD Channel >>> MO3 # 2 >>> VRS Channel 2 >>> CHP portables (multiple)

To further complicate things - it might be good to get even more detailed in this discussion by incorporating specific frequencies, specific NACs, and specific channel usages (such as MO3 output channel - MO3 input channel - portable transmit channel - portable receive channel - etc)

 

[Sac916]

Interesting read about CHPERS http://home.comcast.net/~tr1car1/System Enhancements Rev 04.3r4 - No Markups-Complete.pdf

 

[officer_415]

mlangeveld - I really think your trying to put lipstick on a Palin. But I have to admit I have not put a lot of thought into your recent comments yet.

I think that the system will work like this. If CHP Car 1 chases someone into a neighborhood, then CHP Officer 1 will chase the suspect with his portable on VRS1 which will be connected to CHP Channel 1. CHP Officer 2 who arrives in CHP Car 2 will set his portable to VRS 2 and set his mobile radio to the local police agency channel. Any subsequent CHP officers who arrive at the scene can chose either VRS1 or VRS 2. I would imagine that the safest scenario would pair up CHP officers - one on VRS 1 and one on VRS 2.

Of course it would probably be nice to scan a few CLEMARS and other local PD channels (maybe even a local PD tac channel), but I dont see how that can be accomplished if CHP just has 2 VRS channels allocated by radio zone.

The comments about "priority features" dont ring totally correct to me. I cant imagine that anyone wants a system where you can only monitor 1 and half channels.

I'm not telling you how I think the system should work, I'm telling you HOW IT ACTUALLY WORKS. The problem with the model you just suggested is that Officer 1 cannot talk to Officer 2. When two officers are chasing a suspect, the ability to communicate with each other is pretty important. The scenario you describe, where each responding officer switches to a different channel, does not play out in real life.

The bottom line is that with the old extenders, they could only access one channel: the lowband channel selected in the patrol car. The 700 MHz extenders give them the ability to access any channel (low band, high band, UHF, and 700/800 MHz) programmed in the car's radios. This is an improvement.

 

[WayneH]

Interesting read about CHPERS http://home.comcast.net/~tr1car1/System Enhancements Rev 04.3r4 - No Markups-Complete.pdf

Thanks for reminding me I up'd that. I'll leave it up for a little longer.

 

[zerg901]

" When two officers are chasing a suspect, the ability to communicate with each other is pretty important. "

Pick your poison - CHP can just talk to themselves - or they can have direct comms with local police agencies - looks like they cant really have both.

Looking at http://home.comcast.net/~tr1car1/System Enhancements Rev 04.3r4 - No Markups-Complete.pdf it seems that the new portables are "700 Mhz only" - but they can select various NACs which allows them to connect to various channels via the MO3.

If CHP comes up with a statewide VRS channel, and simuled up 42.34, then for any major incident - VRS 1 could be linked to the local CHP radio zone - VRS 2 could be linked to the local police agency channel or CLEMARS - "VRS Statewide" could be linked to 42.34. If you had 3 CHP officers at the Incident Command Post with 3 portables, they would be able to have pretty good coordination capabilities.

Or - VRS1 could be linked to the local CHP radio zone - VRS2 could be operated as an onscene FB2T - VRS Statewide could be linked to 42.34 - and 700 Mhz mutual aid channels could also be used. This would give multi levels of coverage at a incident scene - 1 or 2 channels for direct short range comms - 1 channel for onscene port to port comms via a onscene repeater - 1 channel for local radio zone CHP coverage (maybe countywide) - 1 channel for statewide coverage (if needed - this could be scaled down to area / countywide coverage).

Come to think of it - maybe the most bang for the buck would be to have 42.34 repeaters statewide - and maybe 45.00 repeaters statewide (or some 2nd low band channel). Then you could have - for each CHP radio zone - VRS 1 for local radio zone - VRS Statewide 1 for 42.34 - VRS Statewide 2 for 45.00. In this case, CHP would have the immediate ability to put 3 wide area nets in use at any incident. This could be useful if they were chasing a gunman through a hilly area.

The possibilitys are endless. Or not.

 

[officer_415]

Come to think of it - maybe the most bang for the buck would be to have 42.34 repeaters statewide - and maybe 45.00 repeaters statewide (or some 2nd low band channel). Then you could have - for each CHP radio zone - VRS 1 for local radio zone - VRS Statewide 1 for 42.34 - VRS Statewide 2 for 45.00. In this case, CHP would have the immediate ability to put 3 wide area nets in use at any incident. This could be useful if they were chasing a gunman through a hilly area.

We covered this before. They did have 42.34 repeaters statewide, and they didn't like it. They are moving toward division-wide channels instead.

The possibilitys are endless. Or not.

As KMA367 already said, you can only plan for so many possibilities. If they have three VRS channels, someday they will wish they had four. With four they may need six. At the end of the day, the system works, and it's an improvement over the old system. There's always going to be room to make it better.

 

[inigo88]

Not to mention they already have 15 or so VRS channels, it just so happens only two are assigned per division. I bet if they really needed it their dispatcher could allocate additional channels. As far as scanning other agencies, you don't need one VRS per channel, you need one per (mobile) radio. If the officer is working in a county where all the local LE is on VHF, then you'd only need one VRS channel to talk to the VHF radio on, and you would talk on different VHF channels by changing the NAC.

This isn't really that complicated, you guys are just making it complicated.

 

[officer_415]

As far as scanning other agencies, you don't need one VRS per channel, you need one per (mobile) radio. If the officer is working in a county where all the local LE is on VHF, then you'd only need one VRS channel to talk to the VHF radio on, and you would talk on different VHF channels by changing the NAC.

Just to clarify, you only need one VRS channel per patrol vehicle. There are multiple radios in the car's trunk, and the officer can access all of them using the same VRS frequency. But I think your point was that multiple VRS channels for are unneccessary for each area, and we definitely agree on that.

 

[inigo88]

Just to clarify, you only need one VRS channel per patrol vehicle. There are multiple radios in the car's trunk, and the officer can access all of them using the same VRS frequency. But I think your point was that multiple VRS channels for are unneccessary for each area, and we definitely agree on that.

Sorry, in his scenario: One officer trying to talk to one patrol vehicle on the lowband, second officer trying to talk to mutual aid units through VHF in second patrol vehicle.

 

[officer_415]

Sorry, in his scenario: One officer trying to talk to one patrol vehicle on the lowband, second officer trying to talk to mutual aid units through VHF in second patrol vehicle.

Gotcha, in which case the alternate VRS channel would be sufficient. It would be a rare scenario where CHP officers at the same scene would need to operate on 3 different channels at the same time.

 

[ScannerDude244]

If you want a good look on how the setup is check it out here CALIFORNIA HIGHWAY PATROL RADIO 2003

 

[lbfd09]

Something to remember with the inter-agency multi band communications issues, many if not all areas in California are adressing this much like our county is with cross-band linked repeaters that give CHP the ability to link in. Biggest problem once these systems are in place is to get the agencies to use them. Fire has beem doing this type of channel switching for more years than I'd like to admit, but other agencies are just now learning of this ability. Simply stated, the CHP HTs in our county are able to access these repeaters and problem solved. (Yeah, they be a few more bells and whistles, but those can varry from CHP office to office.)