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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.

In some urban areas the base station transmission may be "simulcast", meaning the same traffic is transmitted simultaneously from multiple sites for greater coverage. A simulcast operation has the advantage of each mobile unit being able to receive all traffic transmitted by the dispatch center no matter where they are in their office area. For example, if an officer is working an incident near the northern boundary of L.A. County on State Highway 14, communicating through Hauser Peak and another officer is at the northern boundary of L.A. near Gorman and communicating through the Tejon electronic site both have their radios set to the CHP "Tan 2." Each officer works from different area offices that share a frequency and each officer can't hear the other officer's electronic site. If all the electronic sites on Tan 2 are simulcast then each officer would hear everything on their frequency regardless of what electronic site it is transmitted from.

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. A good example of a large dispatch area is that of Bishop, where service is provided to three area offices, #59 - Mojave, #71 Bridgeport, and #72 Bishop. The north-south distance on U.S. 395 in this area is a whopping 285 miles. In this case it takes 7 electronic sites to cover this distance and if one repeater is patching the mobile frequency to the base frequency the mobile units using the other 6 electronic site would not hear the patch or have a very marginal signal if they could hear more than one site. 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 operates on one of 16 statewide extender frequencies on the 700 MHz band and listens for transmissions one of those frequencies from a nearby handheld portable, which are then re-transmitted through the vehicle-mounted radio out on the VHF low band car-to-station (mobile) channel (between 39-46 MHz). When the car radio is receiving traffic on the VHF low band station-to-car (base) channel, that traffic is re-broadcast through the extender unit (if it is enabled) on one of the 700 MHz frequencies. Each extender frequency is used to access a particular frequency pair or "color" and to avoid possible interference from other sources each of the 16 extender frequencies is protected by a digital "network access code," which is similar in function to a CTCSS or DCS tone.

Area offices are equipped with a stationary extender that officers in and nearby the office can use while working there. There are 14 office extender frequencies available statewide.

As of December, 2015 reports were received that 154.905 MHz handheld extenders were still being used. These are being phased out on a schedule agreed to by the FCC as this frequency is being transmitted with a "wideband" signal (25 kHz) instead of a "narrowband" (12.5 kHz) signal required for radios at and above 138 MHz (bottom limit of the VHF-High band). Narrowband use became mandatory on January 1, 2013.

It is important to note that the 700 MHz extender frequencies are used in a digital mode and have a distinctive digital sound. The signal has a strong audio level and the "audio boost" feature on many newer scanner models need not be used on these CHP frequencies.

The handheld radios are programmed with other 700 and 800 MHz frequencies that do not make use of the mobile extender radio, allowing the CHP officer to communicate on county and municipal radio systems, many of those being trunked systems. The handheld can remotely choose frequencies on the VHF-Low (30-50 MHz), VHF-High (138-174 MHz) and UHF (450-512 MHz) bands, thereby allowing communication with agencies that use those bands. The 700 MHz extender links to radios mounted in the trunk, or rear, of each CHP mobile vehicle. Direct communications between handheld extender units is also possible.

Hint: if you are monitoring one of the 16 mobile extender frequencies on 700 MHz on a CA highway and you hear traffic (CHP), there is a good chance you are within less than 1-2 miles of a CHP unit. If your scanner picks up one of the 14 office extender frequencies it is likely that you are within a mile of an area office. This is similar to how a Uniden's Beartracker radio works, picking up nearby mobile and extender frequencies to warn of nearby highway patrol presence.

CHP Enhanced Radio System (CHPERS)

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.

UHF Channel Names by NAC


UHF Name NAC (hex) Site Location Channel Name No. Division
UHF1 B1601ReddingREDDING01Northern
UHF1 B1601Resources BuildingGPD SAC01Valley
UHF1 B1601Mount VacaMT VACA01Golden Gate
UHF1 B1601Mount TamalpaisTAMA U101Golden Gate
UHF1 B1601Black MountainBLK MTN01Central
UHF1 B1601Los PinetosLSPO U101Southern
UHF1 B1601Mount ThomTHOM U101Southern
UHF1 B1601JohnstoneJOHN U101Southern
UHF1 B1601Castro PeakCAST U101Southern
UHF1 B1601Star MountainSTAR MTN01Southern
UHF1 B1601Rolling HillsROLL HILL01Southern
UHF1 B2602Tuscan ButteTUSC BUTE02Northern
UHF1 B2602Mount DiabloDIAB U102Golden Gate
UHF1 B2602Fresno State BuildingFRES DTN02Central
UHF1 B2602SantiagoSANTIAGO02Inland
UHF1 B2602Indio CHPINDIO02Border
UHF1 B3603Sugar LoafSGAR LOAF03Northern
UHF1 B3603Loma PrietaLOMA U103Golden Gate
UHF1 B3603Joaquin RidgeJOAQ RDGE03Central
UHF1 B3603CapistranoCAPISTRO03Border
UHF1 B4604BloomerBLOOMER04Valley
UHF1 B4604Sonoma MoutainSONO U104Golden Gate
UHF1 B4604Shirley PeakSHLY PEAK04Central
UHF1 B4604Cuyamaca PeakCUYA U104Border
UHF1 B5605Twin Peaks City/CntyTWPK CITY05Golden Gate
UHF1 B5605TelegraphTELEGRAP05Central
UHF1 B6606OaklandOAKL U106Golden Gate
UHF1 B6606Mount OsoMT OSO06Central
UHF1 B6606Snow PeakSNOW U106Inland
UHF1 B7607Brockway SummitBKWY SMT07Valley
UHF1 B7607Bald MountainBALD MTN07Valley
UHF1 B7607Pise MountainPISE MTN07Golden Gate
UHF1 B7607Santa YnezSNTA YNEZ07Coastal
UHF1 B7607BridgeportBDGR PORT07Inland
UHF1 B7607MojaveMOJAVE07Inland
UHF1 B7607StrawberrySTRY U107Inland
UHF1 B7607Box SpringBOX SPRG07Inland
UHF1 B8608Cobb MountainCOBB MTN08Northern
UHF1 B8608Tahoe City DOTTAHO CITY08Valley
UHF1 B8608Stockton State BuildingSTKN DTN08Valley
UHF1 B8608San Jose Co. BuildingSNJS U108Golden Gate
UHF1 B8608Mount LoweMT LOWE08Coastal
UHF1 B8608TemeculaTEMECULA08Border
UHF1 BDIR609North CarNRTH CAR09Northern Offices
UHF1 BDIR609Valley CarVLLY CAR09Valley Offices
UHF1 BDIR609Ven / Bar CarVNBR CAR09Coastal Ventura/Santa Barbara Offices Only
UHF1 BDIR609Central CarCNTL CAR09Central Offices
UHF1 BDIR609Inland Car2INLD CAR209Inland
UHF2 C1611Resources BuildingSAC PATROL12Valley
UHF2 C1611Los PinetosLSPO U212Southern
UHF2 C1611HauserHAUSER12Southern
UHF2 C1611Mount ThomTHOM U212Southern
UHF2 C1611JohnstoneJOHN U212Southern
UHF2 C1611Castro PeakCAST U212Southern
UHF2 C1611Mount LeeMT LEE12Southern
UHF2 C1611LACC - LA CommCtrLACC12Southern
UHF2 C1611Junipero Serra State BldgJUNIPERO12Southern
UHF2 C1611San Pedro HillSNPO HILL12Southern
UHF2 C3613Santa Ana State BldgSNTA DTN14Border
UHF2 C4614Cuyamaca PeakCUYA U215Border
UHF2 C5615San Bernardino State BldgSNBD DTN16Inland
UHF2 C6616Snow PeakSNOW U217Inland
UHF2 C7617StrawberrySTRY U218Inland
UHF2 C8618UC San Diego Med CtrUCSD MED19Border
UHF2 CDIR619Inland Car1INLD CAR120Inland Offices
UHF2 CDIR619LA CarLA CAR20Southern Offices
UHF2 CDIR619Border CarBRDR CAR20Border Offices
UHF3 A1621Mount TamalpaisTAMA U321Golden Gate
UHF3 A2622Mount DiabloDIAB U322Golden Gate
UHF3 A3623Loma PrietaLOMA U323Golden Gate
UHF3 A4624Sonoma MoutainSONO U324Golden Gate
UHF3 A5625Twin Peaks DOTTWPK U325Golden Gate
UHF3 A6626OaklandOAKL U326Golden Gate
UHF3 A8628San Jose Co. BuildingSNJS U328Golden Gate
UHF3 ADIR629Gate1 CarGAT1 CAR29Golden Gate Offices
UHF3 ADIR629Mon / Gil CarMNGL CAR29Coastal Monterey/Gilroy Offices Only
UHF4 D1631Twin Peaks DOTTWPK U432Golden Gate
UHF4 DDIR639Gate2 CarGAT2 Car33Golden Gate Offices

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

External Links

Air Unit Callsigns

          • LAST UPDATED 02/22/2018*****
 Northern Division, Redding
 Air11 / 2000 Cessna T206H / N511HP
 Air13 / 2001 Cessna T206H / N513HP
   H14 / 2014 Eurocopter AS350B3 A-Star / N976HP
   H16 / 2014 Eurocopter AS350B3 A-Star / N979HP
 Valley Division, Auburn
   H20 / 2014 Airbus AS350B3 A-Star / N974HP
 Air21 / 2013 Gippsaero GA8 TC-320 / N140HP
 Air23 / 2016 Gippsaero GA8 TC-320 / N148HP
   H24 / 2014 Airbus AS350B3 A-Star / N978HP
 Golden Gate Division, Napa
   H30 / 2016 Airbus AS350B3 A-Star / N981HP
 Air31 / 2016 Gippsaero GA8 TC-320 / N153HP
   H32 / 2016 Airbus AS350B3 A-Star / N982HP
 Air37 / 2015 Gippsaero GA8 TC-320 / N137HP
 Central Division, Fresno
   H40 / 2014 Airbus AS350B3 / N975HP
 Air41 / 2016 Gippsaero GA8 TC-320 / N156HP
 Air43 / 2015 Gippsaero GA8 TC-320 / N139HP
 Border Division, Fullerton
   H50 / 
   H64 / 1994 Bell 206L4 Longranger / N4014Z
   H## / 2000 Airbus AS350B3 A-Star / N314HP (Pending)
   H## / 2001 Airbus AS350B3 A-Star / N341HP (Pending)
 Border Division, Thermal
   H52 / 2002 Eurocopter AS350B3 A-Star / N108HP
   H60 / 
 Coastal Division, Paso Robles
   H70 / 2016 Airbus AS350B3 A-Star / N983HP
 Air73 / 2006 Cessna T206H (G-1000) / N553HP
 Inland Division, Apple Valley
   H80 / 2001 Eurocopter AS350B3 A-Star / N811HP
 Air81 / 2000 Cessna T206H / N881HP
   H82 / 2000 Eurocopter AS350B3 / N414HP
 Air83 / 2000 Cessna T206H / N883HP
 Air## / 2000 Cessna 182S / N537HP
   H## / 2001 Eurocopter AS350B3 / N617HP
   H## / 1999 Eurocopter AS350B3 / N708HP

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