CHP Proximity Alert / "BearTracker" Tip

[hotdjdave]

I have a Uniden BCT7, that had a highway patrol proximity warning system, known as "BearTracker." The system worked by tuning into the highway patrol frequency of a particular state that was used as the mobile extender channel.

When a highway patrol officer got out of the police car (or sometimes while parked on the side of the highway/freeway), the officer would activate the mobile extender to allow his or her handheld radio to communicate with the car radio. The handheld radio is on a different frequency than the car radio. Being this mobile extender used less power than the main car radio, hearing the transmission usually means that you are within close proximity of that transmission (normally less than 3 miles).

So when the radio receives a transmission from this preprogrammed frequency, it would set off an audible alert (alarm) and immediately tune to that frequency.

I no long use my BCT7, so here is what I did on my Uniden BCD396T. For all my CHP groups, I also have the CHP mobile extender frequency (154.905 MHz) as a non-assigned channel. I have three of them, being CHP uses different CTCSS tones for each, one for car2car, car2station, and mobile2mobile, and have ID'd them as such. I assigned a separate alert tone for each type and set them as a "priority" channel.

This accomplishes the same results as Uniden's BearTracker feature.

I took this one step further. Not only did I program the base (output) for each CHP channel, but I also programmed the mobile (input) for each CHP channel. Being input transmissions are coming from the car's relatively low-powered radio and not from a high-powered mountaintop, tower, or rooftop repeater, I know I am in close proximity of that transmission. I take into consideration the quality of the transmission (static, etc.) and the meter on the radio to determine about how far the transmission is from me. The clearer the transmission gets, the closer I am getting.

This concept holds true with other agencies that use the base/mobile model, like CHP, or the semi-duplex model like LAPD or LASO.

One drawback to this whole thing for me is that sometimes in the Los Angeles Metro area (SoCal), you are usually within 3 or so miles from one or more freeways, and usually within 5 or so miles from a CHP unit. Hearing a transmission on a mobile extender could be literally two freeways over.

 

[weeksben1]

I'm wondering if your idea might work on GRE digital scanners as well.

 

[ScannerDude244]

One drawback to this whole thing for me is that sometimes in the Los Angeles Metro area (SoCal), you are usually within 3 or so miles from one or more freeways, and usually within 5 or so miles from a CHP unit. Hearing a transmission on a mobile extender could be literally two freeways over.

Good tip hotdjdave! yeah to many freeways in LA to tell where there at. Well I don't use alert tones on the br330t I just listening for the roger beep the mobile extender sends out after they transmit we only have 101 here so i know they are close by.

 

[hotdjdave]

I'm wondering if your idea might work on GRE digital scanners as well.

If you can set a channel as a priority or put the channel in all your systems, and assign an alert tone or alarm to that channel, it should. Even if you don't have the alert/alarm feature, it will still work, you just have to pay attention to what channel your scanner stops on when receiving traffic.

 

[jmm346]

I no long use my BCT7, so here is what I did on my Uniden BCD396T. For all my CHP groups, I also have the CHP mobile extender frequency (154.905 MHz) as a non-assigned channel. I have three of them, being CHP uses different CTCSS tones for each, one for car2car, car2station, and mobile2mobile, and have ID'd them as such. I assigned a separate alert tone for each type and set them as a "priority" channel.

Why program all three in? Why not just program one in with carrier squelch and set that one to priority? Do you really care which tone is being used?

 

[hotdjdave]

Why program all three in? Why not just program one in with carrier squelch and set that one to priority? Do you really care which tone is being used?

Yes, this way I know if the traffic is the officers are talking to each other (sometims they use this by tag-teaming radar enforcement: one unit clocks, the other pulls over the violator down the road -- I'm not sure if this is legal, but I've seen (heard) them do it) or it is just general dispatch traffic over the air. Also, if you tone out one CTCSS channel, you lose the other; CSQ allows all traffic; so a tone for each one gives me the best audible alert as to what I am hearing without having to look at the scanner or listen for a few seconds to hear what is being transmitted to figure out which one is being used.

I don't use alert tones for anything else, anyway. I've been thinking of assigning alert tones to the CHP mobile channels, though.

 

[jmm346]

Yes, this way I know if the traffic is the officers are talking to each other (sometims they use this by tag-teaming radar enforcement: one unit clocks, the other pulls over the violator down the road -- I'm not sure if this is legal, but I've seen (heard) them do it) or it is just general dispatch traffic over the air. Also, if you tone out one CTCSS channel, you lose the other; CSQ allows all traffic; so a tone for each one gives me the best audible alert as to what I am hearing without having to look at the scanner or listen for a few seconds to hear what is being transmitted to figure out which one is being used.

I don't use alert tones for anything else, anyway. I've been thinking of assigning alert tones to the CHP mobile channels, though.

Which PL tones are you using on the three channels?

 

[hotdjdave]

Tones

Which PL tones are you using on the three channels?

Tones are CTCSS (PL)

• 173.8 Car-to-Station
• 186.2 Car-to-Car
• CSQ HT-to-HT

 

[Duster]

Tones are CTCSS (PL)

• 173.8 Car-to-Station
• 186.2 Car-to-Car
• CSQ HT-to-HT

You might want to confirm your C-to-C PL. It is actually 156.7, confirmed by usage and official documentation.

Are you getting hits with that PL? I'm not aware of 186.2 being used in the extenders at all.

 

[gmclam]

Tones are CTCSS (PL)

• 173.8 Car-to-Station
• 186.2 Car-to-Car
• CSQ HT-to-HT

Are you saying that you program the extender frequency (154.905) 3 times, once with each of the 3 tones above? I run the extender in CSQ displaying a CT and never see a CT. Are these tones used in one particular part of the state? Or is my understanding way off? Thanks.

 

[hotdjdave]

What I listed is statewide (except Plumas County, which uses 153.935). CHP officers carry a 6-channel handheld radio (HT). The first two channels link to the vehicle extender/car radio. These HT radios have the following channels in them:

Chnl Description      Frequency    Tone
1    Car to Station   154.905      173.8
2    Car to Car       154.905      186.2 (156.7 in a few areas)
3    Direct           154.905      CSQ
4    CLEMARS          154.920      CSQ
5    CALCORD          156.075      CSQ
6    NLEMARS          155.475      CSQ

I actually have all six programmed, but only 1, 2, and 3 with alert tones/alarms.

 

[jmm346]

Tones are CTCSS (PL)

• 173.8 Car-to-Station
• 186.2 Car-to-Car
• CSQ HT-to-HT

If you hear the mobile extender cutting out every second or so (priority sampling), you know its the mobile transmitting while checking for a HT that may be trying to transmit.

If you do not hear the mobile extender doing the priority sampling, you know someone with a HT is transmitting.

If the signal is strong, its relatively close to you. If the signal is not strong its relatively far away from you. No need for a PL to determine if a transmitting unit is close to you.

I can understand if you're sampling three different frequencies, but checking one frequency for different PL tones to determine how close a transmitter is to you is a bit overkill for duplicating the BearTracker function. Especially when you consider you mostly hear the csq channel meaning your scanner is constantly checking for whatever tones you have programmed on the other two channels. Meanwhile the CHP mobile extender is doing its own priority sampling. Lots of cutting in and out.

Maybe the new 700mhz mobile extenders will have different frequencies for each function, at which point your tri-channel priority system would be more useful. In the meantime, letting my ears and brain figure out how close a transmitter is works better for me.

 

[hotdjdave]

I can understand if you're sampling three different frequencies, but checking one frequency for different PL tones to determine how close a transmitter is to you is a bit overkill for duplicating the BearTracker function.

I don't use the PL tones to determine how close a unit is...I didn't write that. I use the PL tone to determine with whom the officer is communicating; hence the reason the CHP uses three channels. I want to know what channel they are using. This gives me insight as to what they might be doing (as I listed in previous posts). They use the three different channels for different reasons.

:wink:

 

[jmm346]

I don't use the PL tones to determine how close a unit is...I didn't write that. I use the PL tone to determine with whom the officer is communicating; hence the reason the CHP uses three channels. I want to know what channel they are using. This gives me insight as to what they might be doing (as I listed in previous posts). They use the three different channels for different reasons.

:wink:

Again, I find it easy to figure out who is being spoken to by listening to the nature of the comms with csq. But if programming three channels with PL to know what exact channel they're communicating on works for you, have at it. There isn't much to be gained by knowing the actual channel the HT is on that can't be determined from listening.

 

[hotdjdave]

Again, I find it easy to figure out who is being spoken to by listening to the nature of the comms with csq. But if programming three channels with PL to know what exact channel they're communicating on works for you, have at it. There isn't much to be gained by knowing the actual channel the HT is on that can't be determined from listening.

"To each, his own"...I guess???"

For me, it's instantaneous knowledge without having to listen in for a few to figure it out. For example, I know right away if the comm is HT to HT, which means there are two units within close proximity; if it were on one of the other channels, probably only one unit within close proximity. Also, like I wrote before, many times when they do HT to HT, one is clocking (RADAR or LASER) and communicaiting the the next unit just down the road for the pull-over.

Another analogy would be when a system is set up for simplex/semi-duplex. When a unit communicates in semi-duplex (AKA duplex or repeater), the unit is going through the repeater and communicating with the dispatcher (unit-to-station). The transmission is on the input (w/tone), but everyone hears the transmission on the output (w/tone). When they transmit in simplex, they are communicating unit-to-unit. Even though the frequency may be the same on the output, but not using the same tone or no tone at all, I'd want to program in both channels (same freq w/ diff tones or CSQ) so I knew when it was U2S or U2U.

While on the road, a few seconds makes a difference.

 

[davidmc36]

Nice concept. It amazes me some of the ideas that people come up with to use our new generation of toys. I am going to work on a scheme to use with our local Boys in Blue. It will in all likelihood be a relatively similar copy of what you did.

Ontario Provincial Police Scanner Frequencies and Radio Frequency Reference

 

[radioprescott]

And wouldn't the CSQ programmed channel receive "all" traffic regardess of the PL transmitted? Unless you lock out that PL tone (if you have that capability - and I believe you can only lock out one tone per channel) you will still recevie all the traffic when stopped on the CSQ channel.

Or is MY understanding way off too?

By the way I stole, er I mean adapted this idea for AZ Highway Patrol, using the repeater input freqs. Seem to be working fairly well. Thanks for the idea!

 

[NWtoSFO]

It's a nice idea that Dave found, and I'll probably try with one of my scanners. Part of getting a scanner with text tags is having that instant knowledge as soon as it stops on a frequency. I don't know if it would take more than a couple of seconds to figure out that one patrol officer is talking to another just down the road, though. I listen to Roseville PD everyday at work, and when the motor units are setup at an intersection they use channel 4, but I don't need to see the channel to know that they are talking to each other. I'm sure the CHP units talking to each other isn't any different. Nonetheless, I want to sit up off of 80 and see how well this concept works.

 

[hotdjdave]

And wouldn't the CSQ programmed channel receive "all" traffic regardess of the PL transmitted? Unless you lock out that PL tone (if you have that capability - and I believe you can only lock out one tone per channel) you will still recevie all the traffic when stopped on the CSQ channel.

Or is MY understanding way off too?

Well, if you just put in one channel on CSQ, then, yes, you would hear all the traffic. However, that would defeat my purpose: I want to selectively and instantaneously know what channel they are using. This is why I assign a channel in my radio with a different alarm tone for each of the three CHP channels.

 

[radioprescott]

Well, if you just put in one channel on CSQ, then, yes, you would hear all the traffic. However, that would defeat my purpose: I want to selectively and instantaneously know what channel they are using. This is why I assign a channel in my radio with a different alarm tone for each of the three CHP channels.

Just a question on the technical aspect of this:

It has been my experience with the 396 that Setting the CTCSS/DCS "Off" (essentially CSQ) passes all transmissions. Likewise setting a CTCSS or DCS tone passes only the transmissions with that tone. Setting the priority affects the frequency.

As I understand it, you programmed the same freqs in 3 channels: 2 channels with PL and 1 with CSQ. You set priority for all 3 channels.

Doesn't the CSQ channel pass transmissions with either of the other PL tones (or any PL or no PL) if the transmissions was received on the CSQ channel?

The techno-nut part of my brain is trying to understand how a CSQ channel will pass only CSQ traffic.

It's a neat idea, and as I mentioned it works for me in AZ with all PL tone and no CSQ channels.