Department of the Highway Patrol (CHP) (CA)
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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||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||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 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 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||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 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||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
Air Unit Callsigns
- THIS LIST IS UPDATED AS INFORMATION BECOMES AVAILABLE
- LAST UPDATED 3/1/2022*
Northern Division, Redding Air11 / N511HP / 2000 Cessna T206H Air13 / N513HP / 2001 Cessna T206H H14 / N976HP / 2014 Airbus AS350B3 A-Star H16 / N979HP / 2014 Airbus AS350B3 A-Star
Valley Division, Auburn H20 / N974HP / 2014 Airbus AS350B3 A-Star Air21 / N159HP / 2018 Gippsaero GA8 TC-320 Air23 / N148HP / 2016 Gippsaero GA8 TC-320 H24 / N978HP / 2014 Airbus AS350B3 A-Star H1 / N708HP / 1999 Eurocopter AS350B3 A-Star - Headquarters Helicopter stationed at McClellan
Golden Gate Division, Napa H30 / N981HP / 2016 Airbus AS350B3 A-Star Air31 / N153HP / 2016 Gippsaero GA8 TC-320 H32 / N982HP / 2016 Airbus AS350B3 A-Star 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 Air81 / N881HP / 2000 Cessna T206H H82 / N985HP / 2019 Airbus AS350B3 A-Star Air83 / N441HP / 2000 Cessna T206H
Southern Division, Fullerton H50 / N341HP / 2001 Eurocopter AS350B3 A-Star Air51 / N140HP / 2013 Gippsaero GA8 TC-320 H58 / N617HP / 2001 Eurocopter AS350B3 A-Star H62 / N314HP / 2000 Eurocopter AS350B3 A-Star
Border Division, Thermal H60 / N988HP / 2021 Airbus AS350B3 A-Star Air63 / N551HP / 2001 Cessna T206H Air61 / N661HP / 2000 Cessna T206H