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. 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.

LEGACY VHF EXTENDER CHANNEL ASSIGNMENTS:

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

THIS LIST IS UPDATED AS INFORMATION BECOMES AVAILABLE
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