Police Radar Bands: X, K and Ka Frequencies

By I Go Cars · Updated October 29, 2026

The three police radar bands, defined

Police radar bands are the three microwave frequency ranges in which traffic radar is designed to operate: X band (10.500 to 10.550 GHz), K band (24.050 to 24.250 GHz) and Ka band (33.4 to 36.0 GHz). Ka band, the widest of the three, is the one used by most radar models on the National Highway Traffic Safety Administration's (NHTSA) 2022 Conforming Product List.

A frequency band is a defined range of radio frequencies; a gigahertz (GHz) is one billion cycles per second. The definitions come from NHTSA's Down-the-Road Radar Module specification (DOT HS 812 266), the federal performance standard for police radar:

X band: designed "to operate in the frequency band of 10,500 MHz to 10,550 MHz" (§1.4.46).
K band: "24,050 MHz to 24,250 MHz" (§1.4.19).
Ka band: "33,400 MHz to 36,000 MHz" (§1.4.20).

NHTSA's 2018 radar instructor manual gives the nominal (center design) frequencies officers are taught: X band at "10,525,000,000 waves per second" (10.525 GHz) and K band at "24,150,000,000 waves per second" (24.150 GHz). For Ka it gives a range rather than one number: "The Ka-band R.A.D.A.R. frequency ranges between 33.4 and 36 gigahertz."

What the band changes, and what it does not

All three measure speed the same way: the radar transmits, the signal reflects off a vehicle, and the Doppler shift (the change in returned frequency caused by motion) is converted into a speed. The band sets the carrier frequency. It does not set the accuracy requirement. NHTSA's specification applies the same tolerances to all three: stationary readings within +1/-2 mph and moving-mode patrol and target speeds within ±2 mph.

Beam width is not a band property either. NHTSA's manual gives a beam range of 9 to 18 degrees depending on the manufacturer, not on the frequency. A driver who hears that one band is "more accurate" than another is hearing marketing, not the specification.

X band: still defined, rarely listed

X band is the oldest and lowest of the three police bands, centered on 10.525 GHz. NHTSA still defines it, and the specification still applies to it. No federal document reviewed for this page says X band is prohibited or withdrawn, and no agency statement calling it obsolete was found.

What the documents do show is a shift in equipment. NHTSA's Conforming Product List (CPL), the list of radar models that passed independent testing against the specification, dated November 28, 2022, lists mostly Ka-band down-the-road radars, a few K/Ka units, and one X/K/Ka unit, the MPH Python III. The accurate framing is that X is rare in currently listed equipment, not that it has been banned.

X band also has a crowded neighborhood. Microwave motion sensors on automatic doors operate there; one manufacturer's sensor sheet (the Malibu Club Systems MAC-015-MS, a "Microwave Motion Sensor for automatic door") lists "X_Band 10.525GHZ," the same nominal frequency NHTSA gives for police X band. That is why a detector can sound X-band alerts near shopping centers with no patrol car present.

K band and the blind-spot radar problem

K band runs from 24.050 to 24.250 GHz, with a nominal police frequency of 24.150 GHz. It is the range that produces the most confusion, because cars now carry radar of their own.

HELLA's automotive rear radar, used for blind-spot monitoring, lane change assist and rear cross traffic alert, is specified at "24.15 GHz/ISM" with a bandwidth of 200 MHz or less, using "24 GHz narrowband technology." ISM refers to the industrial, scientific and medical frequency allocation. That is the same nominal frequency NHTSA gives for police radar in this range. DENSO has described a "24GHz submillimeter-wave" rear-side radar that detects vehicles entering the blind spot, used in the 2018 Toyota Camry, according to trade-press reporting of the company's release.

The Federal Communications Commission (FCC), which regulates radio emitters, addressed these frequencies in a 2017 Report and Order (FCC 17-94). It barred the manufacture, import, sale and installation of wideband and ultra-wideband vehicular radar in the 22 to 29 GHz range after January 1, 2022, and moved new automotive radar to 76 to 81 GHz. It also said narrowband vehicular radars at 24.075 to 24.175 GHz under 47 CFR 15.245 "are not being modified" and "can continue to be used in vehicular applications." That narrowband slice sits entirely inside NHTSA's police allocation of 24.050 to 24.250 GHz.

The same Order names blind-spot detectors as an example of short-range radar intended for 76 to 81 GHz. The reasonable reading is that newer vehicles may use 77 GHz systems while older or narrowband designs still emit at 24 GHz. Which specific current models use which frequency was not verified for this page. The conclusion a driver needs is narrower: a K-band alert does not by itself mean police radar.

Ka band: a range, not a single frequency

Ka band runs from 33.4 to 36.0 GHz. NHTSA's SMD Glossary, the defined-terms list for its Speed-Measuring Device Operator Training, puts it this way: "The FCC currently permits police traffic R.A.D.A.R. operation anywhere within the range between 33.4 to" 36.0 GHz. The specification adds a stability requirement: §2.6.1 limits a Ka-band unit's output to within ±100 MHz of its nominal frequency.

Radar detector makers commonly cite particular Ka sub-frequencies, such as 33.8, 34.7 and 35.5 GHz. Those figures were not found in an NHTSA or FCC document during research for this page, so they are reported here as industry figures only. The federal documents describe the range as a whole.

The 2022 CPL's predominance of Ka-band units is the documentary basis for saying that Ka is the frequency range most current listed police radar uses. NHTSA announced in a November 2024 Federal Register notice that it would discontinue the radar CPL after one year and move to industry verification built on IEEE Standard 2450, so the 2022 list may now be historical.

Instant-on radar and standby mode

"Instant-on" is the common name for radar held in standby and switched on only to take a reading. In standards language it is standby mode, defined in §1.4.37 of the NHTSA down-the-road radar specification as "the state of a radar device in which power to the microwave oscillator is inhibited." The transmitter is off, so there is nothing to detect.

The specification's requirement is about accuracy, not timing: "Switching the radar device from standby to ON shall not cause any erroneous speed readings with a target present" (§2.11). No standby-to-reading time limit is set. Section 2.6.6 also describes a Standby/Operate switch that "must be held depressed for the radar device to transmit"; which device class that applies to is not confirmed here.

The consequence for a detector user is an inference, not a sourced statement: when radar is used in standby, a warning depends on the detector picking up readings taken on other vehicles ahead. The targeted vehicle itself may receive no warning before the reading.

Other things that set off radar-band alerts

NHTSA's training lists sources that interfere with police radar itself: mercury vapor, neon and fluorescent lights; roof air-conditioning fans and other mechanical devices; and radios inside or near the patrol car. Those affect the police unit's readings rather than a driver's detector, but they show how busy the microwave environment around a road can be.

For a driver, the picture across the three is consistent. X-band alerts often trace to automatic-door sensors at 10.525 GHz. K-band alerts often trace to 24 GHz automotive radar at or near 24.15 GHz. The documents consulted for this page identify no common non-police emitter in the Ka range, at 33.4 to 36.0 GHz. None of this site's pages rate or compare radar detectors.

Frequently asked questions

What frequency is K band radar?

K band police radar operates between 24.050 and 24.250 GHz, according to NHTSA's down-the-road radar specification (DOT HS 812 266, section 1.4.19). NHTSA's 2018 training manual gives the nominal police K-band frequency as 24.150 GHz. Narrowband automotive radars at 24.075 to 24.175 GHz, used for blind-spot monitoring, sit inside the same range.

What is Ka band radar?

Ka band is the police radar allocation from 33.4 to 36.0 GHz. NHTSA's SMD Glossary says the FCC permits police traffic radar operation anywhere within that range, and the specification requires each unit to hold within plus or minus 100 MHz of its own nominal frequency. Most radars on NHTSA's 2022 Conforming Product List were Ka-band units.

Do police still use X band radar?

X band is rare in currently listed equipment, but it has not been banned. NHTSA still defines X band at 10.500 to 10.550 GHz, and its November 2022 Conforming Product List included one X/K/Ka unit, the MPH Python III, among mostly Ka-band radars. No agency statement calling X band obsolete was found.

Why does my radar detector go off on K band with no police around?

Many vehicles carry blind-spot radar in the same 24 GHz range police use. HELLA's rear radar runs at 24.15 GHz, the nominal police K-band frequency, and a 2017 FCC Order allowed narrowband 24 GHz vehicular radars to continue in use. A K-band alert therefore does not by itself indicate a police radar unit.

Why does X band go off near stores?

Automatic-door motion sensors commonly operate in X band. One manufacturer's sensor sheet lists its automatic-door microwave sensor at 10.525 GHz, the same nominal frequency NHTSA gives for police X-band radar. A detector cannot distinguish the two by frequency alone, so shopping centers produce frequent X-band alerts.

What is instant-on radar?

Instant-on radar is radar held in standby, with its transmitter off, and switched on only to take a reading. NHTSA's specification defines standby as the state in which power to the microwave oscillator is inhibited, and requires that switching from standby to on cause no erroneous speed reading with a target present. It sets no time limit.

Is Ka band radar more accurate than K or X band?

No. NHTSA's specification applies the same accuracy tolerances to all three: +1/-2 mph in stationary mode and plus or minus 2 mph for moving-mode patrol and target speeds. The band determines the transmitted frequency, not the required accuracy, and each one measures speed through the same Doppler principle.

Police radar bands: X, K and Ka