Department of the Highway Patrol (CHP) (CA)

From The RadioReference Wiki

(Redirected from California 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. The state requested a waiver for the narrowband mandate until the end of 2018, by which point all VHF extenders will be removed from service.

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.


CH 1: 154.905 Simplex, 173.8 PL for Car to Station (S)

CH 2: 154.905 Simplex, 186.2 PL for Car to Car (C)

CH 3: 154.905 Simplex, CSQ, Portable to Portable

CH 4: 154.920 Simplex, CLEMARS mutual aid

CH 5: 156.075 Simplex, CALCORD Mutual Aid

CH 6: 155.475 Simplex, NALEMARS National Mutual Aid

Channels 7-16 were normally programmed locally to communicate with other public safety systems on the same VHF band within the local geographic area as the CHP area office of the radio being used. In Plumas County, 155.445 was used instead of the statewide frequency of 154.905.

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.

Possible Future Use Frequencies


45.28000 KMK259 B 151.4 PL LIME COA B Lime - Base - Santa Barbara (29) FM Law Dispatch
42.72000 KA4993 M 151.4 PL LIME COA M Lime - Mobile - Santa Barbara (29) FM Law Dispatch

UHF Name NAC (hex) Site Location Channel Name No. Division
UHF1 B1 601 Redding REDDING 01 Northern
UHF1 B1 601 Resources Building GPD SAC 01 Valley
UHF1 B1 601 Mount Vaca MT VACA 01 Golden Gate
UHF1 B1 601 Mount Tamalpais TAMA U1 01 Golden Gate
UHF1 B1 601 Black Mountain BLK MTN 01 Central
UHF1 B1 601 Los Pinetos LSPO U1 01 Southern
UHF1 B1 601 Mount Thom THOM U1 01 Southern
UHF1 B1 601 Johnstone JOHN U1 01 Southern
UHF1 B1 601 Castro Peak CAST U1 01 Southern
UHF1 B1 601 Star Mountain STAR MTN 01 Southern
UHF1 B1 601 Rolling Hills ROLL HILL 01 Southern
UHF1 B2 602 Tuscan Butte TUSC BUTE 02 Northern
UHF1 B2 602 Mount Diablo DIAB U1 02 Golden Gate
UHF1 B2 602 Fresno State Building FRES DTN 02 Central
UHF1 B2 602 Santiago SANTIAGO 02 Inland
UHF1 B2 602 Indio CHP INDIO 02 Border
UHF1 B3 603 Sugar Loaf SGAR LOAF 03 Northern
UHF1 B3 603 Loma Prieta LOMA U1 03 Golden Gate
UHF1 B3 603 Joaquin Ridge JOAQ RDGE 03 Central
UHF1 B3 603 Capistrano CAPISTRO 03 Border
UHF1 B4 604 Bloomer BLOOMER 04 Valley
UHF1 B4 604 Sonoma Moutain SONO U1 04 Golden Gate
UHF1 B4 604 Shirley Peak SHLY PEAK 04 Central
UHF1 B4 604 Cuyamaca Peak CUYA U1 04 Border
UHF1 B5 605 Twin Peaks City/Cnty TWPK CITY 05 Golden Gate
UHF1 B5 605 Telegraph TELEGRAP 05 Central
UHF1 B6 606 Oakland OAKL U1 06 Golden Gate
UHF1 B6 606 Mount Oso MT OSO 06 Central
UHF1 B6 606 Snow Peak SNOW U1 06 Inland
UHF1 B7 607 Brockway Summit BKWY SMT 07 Valley
UHF1 B7 607 Bald Mountain BALD MTN 07 Valley
UHF1 B7 607 Pise Mountain PISE MTN 07 Golden Gate
UHF1 B7 607 Santa Ynez SNTA YNEZ 07 Coastal
UHF1 B7 607 Bridgeport BDGR PORT 07 Inland
UHF1 B7 607 Mojave MOJAVE 07 Inland
UHF1 B7 607 Strawberry STRY U1 07 Inland
UHF1 B7 607 Box Spring BOX SPRG 07 Inland
UHF1 B8 608 Cobb Mountain COBB MTN 08 Northern
UHF1 B8 608 Tahoe City DOT TAHO CITY 08 Valley
UHF1 B8 608 Stockton State Building STKN DTN 08 Valley
UHF1 B8 608 San Jose Co. Building SNJS U1 08 Golden Gate
UHF1 B8 608 Mount Lowe MT LOWE 08 Coastal
UHF1 B8 608 Temecula TEMECULA 08 Border
UHF1 BDIR 609 North Car NRTH CAR 09 Northern Offices
UHF1 BDIR 609 Valley Car VLLY CAR 09 Valley Offices
UHF1 BDIR 609 Ven / Bar Car VNBR CAR 09 Coastal Ventura/Santa Barbara Offices Only
UHF1 BDIR 609 Central Car CNTL CAR 09 Central Offices
UHF1 BDIR 609 Inland Car2 INLD CAR2 09 Inland
UHF2 C1 611 Resources Building SAC PATROL 12 Valley
UHF2 C1 611 Los Pinetos LSPO U2 12 Southern
UHF2 C1 611 Hauser HAUSER 12 Southern
UHF2 C1 611 Mount Thom THOM U2 12 Southern
UHF2 C1 611 Johnstone JOHN U2 12 Southern
UHF2 C1 611 Castro Peak CAST U2 12 Southern
UHF2 C1 611 Mount Lee MT LEE 12 Southern
UHF2 C1 611 LACC - LA CommCtr LACC 12 Southern
UHF2 C1 611 Junipero Serra State Bldg JUNIPERO 12 Southern
UHF2 C1 611 San Pedro Hill SNPO HILL 12 Southern
UHF2 C3 613 Santa Ana State Bldg SNTA DTN 14 Border
UHF2 C4 614 Cuyamaca Peak CUYA U2 15 Border
UHF2 C5 615 San Bernardino State Bldg SNBD DTN 16 Inland
UHF2 C6 616 Snow Peak SNOW U2 17 Inland
UHF2 C7 617 Strawberry STRY U2 18 Inland
UHF2 C8 618 UC San Diego Med Ctr UCSD MED 19 Border
UHF2 CDIR 619 Inland Car1 INLD CAR1 20 Inland Offices
UHF2 CDIR 619 LA Car LA CAR 20 Southern Offices
UHF2 CDIR 619 Border Car BRDR CAR 20 Border Offices
UHF3 A1 621 Mount Tamalpais TAMA U3 21 Golden Gate
UHF3 A2 622 Mount Diablo DIAB U3 22 Golden Gate
UHF3 A3 623 Loma Prieta LOMA U3 23 Golden Gate
UHF3 A4 624 Sonoma Moutain SONO U3 24 Golden Gate
UHF3 A5 625 Twin Peaks DOT TWPK U3 25 Golden Gate
UHF3 A6 626 Oakland OAKL U3 26 Golden Gate
UHF3 A8 628 San Jose Co. Building SNJS U3 28 Golden Gate
UHF3 ADIR 629 Gate1 Car GAT1 CAR 29 Golden Gate Offices
UHF3 ADIR 629 Mon / Gil Car MNGL CAR 29 Coastal Monterey/Gilroy Offices Only
UHF4 D1 631 Twin Peaks DOT TWPK U4 32 Golden Gate
UHF4 DDIR 639 Gate2 Car GAT2 Car 33 Golden Gate Offices

Divisional Updates & Status

CHP Offices & Frequencies
Link to Forum Threads for CHP Updates
Excel File All Division Changes as of 2009

External Links

Air Unit Callsigns

  • LAST UPDATED 01/11/2024*
 Northern Division, Redding
   H14 / N976HP / 2014 Airbus AS350B3 A-Star
   H16 / N979HP / 2014 Airbus AS350B3 A-Star
 Air11 / N511HP / 2000 Cessna T206H
 Air15 / N202HP / 2022 Cessna 208B Caravan
 Valley Division, Auburn
    H1 / N708HP / 1999 Eurocopter AS350B3 A-Star - headquarters helicopter stationed at McClellan
   H20 / N974HP / 2014 Airbus AS350B3 A-Star
   H24 / N978HP / 2014 Airbus AS350B3 A-Star
 Air21 / N159HP / 2018 Gippsaero GA8 TC-320
 Golden Gate Division, Napa
   H30 / N981HP / 2016 Airbus AS350B3 A-Star
   H32 / N982HP / 2016 Airbus AS350B3 A-Star
 Air31 / N153HP / 2016 Gippsaero GA8 TC-320
 Air37 / N137HP / 2015 Gippsaero GA8 TC-320
 Central Division, Fresno
   H40 / N975HP / 2014 Airbus AS350B3 A-Star
 Air41 / N156HP / 2016 Gippsaero GA8 TC-320
 Air43 / N139HP / 2015 Gippsaero GA8 TC-320
 Coastal Division, Paso Robles
   H70 / N983HP / 2016 Airbus AS350B3 A-Star
 Air71 / N443HP / 2000 Cessna T206H
 Air73 / N553HP / 2006 Cessna T206H
 Inland Division, Apple Valley
   H80 / N984HP / 2019 Airbus AS350B3 A-Star
   H82 / N985HP / 2019 Airbus AS350B3 A-Star
 Air81 / N441HP / 2000 Cessna T206H
 Air83 / N513HP / 2001 Cessna T206H
 Southern Division, Fullerton
   H50 / N341HP / 2001 Eurocopter AS350B3 A-Star
   H58 / N617HP / 2001 Eurocopter AS350B3 A-Star
   H62 / N314HP / 2000 Eurocopter AS350B3 A-Star
 Air51 / N140HP / 2013 Gippsaero GA8 TC-320
 Border Division, Thermal
   H60 / N988HP / 2021 Airbus AS350B3 A-Star
 Air61 / N661HP / 2000 Cessna T206H
 Air63 / N551HP / 2001 Cessna T206H