Monitoring the California Highway Patrol

[BornWithAScanner]

Is anyone aware of any broadcasting changes with the CHP Dispatch and Unit comms made within the last 5 or 6 years? For some reason, for the past few years, I have been able to hear both sides of the conversation (Dispatch and Unit), but a few years back, I was only able to pick up the dispatch side. Now, I do notice that the CHP cars do not have the long whips like they used to (come to think of it, I haven't seen the whips for years). Should that be my clue?

 

[avascan522]

I rarely monitor them, but I do know they have been transitioning their old analogue VHF vehicular extenders with P25 700 Mhz extender frequencies. I've heard traffic before on the new 700's, but it was too far away and I only caught a few words and garbling. But hey, if you can receive dispatch AND field units on the low band frequencies, more power to ya. I'm happy

 

[AdminLaw]

Golden Gate Division usually has all their mobile traffic rebroadcast on repeater so you will hear both sides of the traffic on the base frequencies.

 

[gmclam]

CHP

There are several threads here on RR on this topic. There have been several changes taking place. Because of the size of the organization, most of the changes take years to complete. Then to top it off, issues came up where one division's signal was interfering with another's; or would interfere if the planned changes took place.

One change is moving from using a VHF extender to a 700MHz P25 based extender. Channels were also added so that offices have 'extenders' too, not just autos.

Another thing done is to (mostly) change the base and mobile frequencies used by any channel pair so that they have some frequency separation (such as 3MHz). This was so that the mobile frequency could be (selectively) 'repeated' back on the base frequency. But this function can be turned on and off by each dispatcher.

Mostly though they are still using low band VHF, and while I know I am odd, I love them there.

 

[BornWithAScanner]

Thank you all for your insight regarding my question about being able to finally listen in on the unit side. It is the Golden Gate division that I scan so that explains why I am able to hear both sides. I am troubled by this P25 stuff. I know, I can buy a new scanner but I really "love" my Pro-39. Side note, I do find it very interesting that the CHP units sound much different than other agencies. I can't put my finger on it but they are different (stronger signal perhaps (no, that's not it), more by the book?, I don't know, what is it?)

thx to all -

 

[gmclam]

What I've noticed with channels that have 'upgraded' or made the changes to enable repeating is that the audio sounds compressed. I think they are able to keep their modulation level nearer to 100% this way and help try to overcome atmospheric noise so prevalent on low band VHF.

When it works, it sounds great. Then there are days when the skip is in or some other interference and it's tough to understand someone who might only be transmitting from a few feet away.

 

[BornWithAScanner]

gmclam,

Thank you for shedding light on this for me. It does make sense. Did you notice skip yesterday? I think I did.

 

[LIScanner101]

BornWithAScanner,

Just wanted to note that I was in your area on 3/4, 3/5 and 3/6 and every CHP car I saw had a black low band whip on it.

 

[ECPD279]

Several years ago the CHP stopped using the fender ball mounted, gigantic 1/4 wave whips, and changed to roof mounted, Larsen base loaded whips. They look different, but they're still on the same VHF Low band.

 

[gmclam]

CHP

gmclam,

Thank you for shedding light on this for me. It does make sense. Did you notice skip yesterday? I think I did.

I try not to notice the skip and just make out what the CHP is saying. Some days it is really rough for sure.