Department of the Highway Patrol (CHP) (CA)
A Beginner's Guide to the CHP Radio System:
The CHP employs two frequencies for communications between units in the field and their dispatch centers. One frequency is used by base stations, located at electronic sites, most of which are placed on mountain peaks or other high positions. Cars, or mobile units, use a second frequency to talk with these base stations. On the list below the base frequency is shown as the "frequency" and the mobile frequency is shown as "input." It is important to realize that base stations transmit from higher elevations and at much greater power than mobile units do. For this reason the base frequency can be heard over long distances, while the lower powered ground level mobile units can only be received if they are close by. The dispatch centers use one or more electronic sites to communicate with mobile units. Remember that high locations are ideal for radio reception as they can "see" more territory than ground level sites. This is why the dispatcher can receive most of the mobile traffic, while the scanner listener cannot.
Electronic sites are linked via microwave or 72 MHz frequencies and the dispatcher's console is controlled by a type of computer that chooses the best signal to send to the dispatcher if more than one site is receiving a mobile unit's signal at the same time. This computer is called a voter, as the selection among multiple sites is "voted" for the best signal. When transmitting to a mobile unit the dispatcher can choose the electronic site they want to use, and normally choose the same site the voter chose when replying to a mobile unit. This is why you may hear the base frequency come in well at times when a nearby site is being used and not so well when another, more distant site is being used.
When units want to communicate directly with each other, commonly referred to as "direct" or "car to car", they both switch their radios to another channel where the radio is both receiving and transmitting on the base frequency. The dispatcher can also monitor these transmissions, and may refer to "Channel 2" when using this mode. One disadvantage to this is the cars can have the same experience that scanner listeners have, which is that they cannot hear other mobile units that are located some distance away. The base station transmission may be "simulcast", meaning the same traffic is transmitted simultaneously from multiple sites for greater coverage.
In some locations within the state, mostly in urban areas, and mostly in southern California, the mobile frequency is patched to the base frequency on the most often used electronic site within a dispatch area. Cars are now able to hear each other from longer distances that they could before. This works the best in dispatch areas that are small and mostly urban as in these areas most mobile units can receive the same electronic site. In rural areas the dispatch area can be quite large with as many as 6-12 sites and mobile units may only be in range of one of those sites. Since the advantage of having the other mobile units hear each other is lost, the mobile traffic is not transmitted over the base frequency in rural areas.
Mobile Extender Handheld Radios
When a CHP officer intends to get out of the patrol vehicle or gets out of the patrol vehicle, the officer activates the mobile extender unit to hear radio traffic and transmit radio traffic over the car radio (higher power) via the officer's handheld portable radio.
The mobile extender unit usually operates on 154.905 MHz, and listens for transmissions on that frequency from a nearby handheld portable, which are then re-transmitted through the vehicle-mounted radio out on the lowband car-to-station channel (between 39-47 MHz). When the car radio is receiving traffic on the lowband dispatch channel, that traffic is re-broadcast through the extender unit (if it is enabled) on 154.905 MHz.
The handheld radios are programmed with other frequencies that do not make use of the mobile extender radio, allowing the CHP officer to talk to other CHP handheld portable radios and other non-CHP radio systems. Channels 7-16 are normally programmed locally to communicate with other public safety systems on the same VHF band within the same geographical area as the radio being used. Beginning in 2010, CHP handheld radios and extenders will be switching to frequencies between 769-775 MHz.
Hint: if you are monitoring 154.905 MHz on a CA highway and you hear traffic (CHP), there is a good chance you are within less than 3 miles of that CHP unit. This is the same technology used in Uniden's Beartracker radios.
CHPERS CHP Enhanced Radio System
The CHP is undergoing a major radio system update. This is a multi year program to upgrade and enhance the statewide system. Here is the brief summary from the program update as of 2009:
"The CHPERS project is a five year effort which will provide for the development and implementation of an enhanced statewide radio communications system in support of CHP’s mission to provide safety, service and security to the public."
The full status update file can be found here:CHPERS Project Status 2009
This program includes upgrading of transmitter sites, field office radio equipment, addition of new frequencies, new 700/800 MHz handheld radios and new vehicle radio systems. It will include capabilities for 700/800 MHz transmission as needed, incorporation of repeater function primarily in urban areas and a revision to the vehicle extenders to operate in the 700 MHz range. In addition, the new vehicle systems called Consolidated Patrol Vehicle Environment (CPVE) will include GRE-PSR 600 Scanners on a remote control head(GRE stated that the PSR 600 does not have a remote head capability, the CHP reference may be premature or refer to a 3rd party modification) along with additional radio equipment in different bands to meet federal interoperability standards for communication with adjacent agencies. This includes the ability to access various regional conventional and trunked systems throughout the state.
The program is being implemented gradually throughout the state. As of November/December 2009, all existing CHP radios have been reprogrammed with updated code plugs to prepare for upcoming changes. As remote transmitter sites are upgraded, new and revised frequency plans are being implemented on a division by division basis. Divisional updates will continue through 2010 and into 2011. CPVE installations are tentatively scheduled to begin in 2010 and continue over a 3 year period. Once all the systems have been purchased and installed, the final configuration will be implemented state wide.
Several California forum threads have links to updated maps and other documents outlining changes and updates as well as field observations of changes being implemented.
As with any capital improvement program in California, delays are occurring. The state has continued to fund the program for 2010, but delays have occurred for different reasons. Information provided on schedules are tentative and expected to slip. Any additional information that can be provided by users can be posted in the applicable divisions below.
Here is the 2012 Legislative update report: CHPERS 2012 Update
This report provides the current status and information on delays and complications to the program.
Divisional Updates & Status
This section has been removed due to ongoing changes and redundency with the database.
CHP Offices & Frequencies
Cleaned Up Version of CHP Freqs from Wayne H
Link to Forum Threads for CHP Updates
Excel File All Division Changes as of 2009