Radar bands explained: X, K, Ka, Ku and laser
Last updated August 2026 · McFlash editorial team · 7 min read
Every detector spec sheet lists bands, and most of that list is marketing. Only two of them decide whether a device is useful on North American roads today: Ka and K. Here is what each band actually is, who uses it, and how to read an alert in real traffic without staring at the display.
Disclosure: McFlash sells the McFlash 360. We name the cases where a different detector — or no detector — is the better buy, and we do not publish figures we have not measured or sourced.
Key takeaways
- Ka-band (33.4–36.0 GHz) is the dominant enforcement band — sensitivity here decides real range.
- K-band is genuine enforcement and the biggest source of false alerts, so filtering matters.
- X-band alerts in most of North America are noise, not police.
- Laser is infrared, not radio, and an alert usually means you were already measured.
- Full Ka segment coverage (33.8, 34.7, 35.5 GHz) beats any headline sensitivity number.
The bands, one by one
| Band | Frequency | What it means for you |
|---|---|---|
| X-band | 10.5 GHz | Rare in US enforcement today. Still used in a few eastern states and by some automatic door sensors, so X alerts are usually false. |
| K-band | 24.15 GHz | Widely used by state and local police. Also the band used by blind-spot monitors and door openers — the main source of false alerts. |
| Ka-band | 33.4–36.0 GHz | The dominant modern enforcement band in the US and Canada. Ka sensitivity is the single most important spec on any detector. |
| Ku-band | 13.45 GHz | Used in parts of Europe, effectively absent from North American roads. Harmless to have. |
| Laser (LIDAR) | 904 nm infrared | Not radio at all. Very narrow beam, so an alert usually means you were already targeted. |
| VG-2 / Spectre | — | Radar-detector detectors used by enforcement in ban jurisdictions. Relevant only where detectors are illegal. |
Why Ka is the band that matters
Ka is not one frequency but a range, and patrol guns cluster in three segments inside it. A detector that sweeps all of them quickly will catch enforcement that a narrower, faster shortcut misses entirely.
| Segment | Status | Why it matters |
|---|---|---|
| 33.8 GHz | Most common US Ka segment | The frequency the majority of modern patrol guns use. |
| 34.7 GHz | Second common segment | Widely deployed; a detector must cover it, not just 33.8. |
| 35.5 GHz | Third segment | Less common but in service — full-segment scanning matters. |
Reading an alert in real traffic
| What you hear | Most likely source | What to do |
|---|---|---|
| Ka, strengthening steadily | Genuine enforcement | Ease off now — this is what a detector exists for. |
| K, brief hard spike near a storefront | Automatic door | Ignore; city filtering should suppress it. |
| K, tracks alongside you in traffic | Blind-spot radar on a nearby car | Ignore; it fades when the car changes lane. |
| X-band, anywhere | Almost always noise | Genuine X enforcement is rare in most of North America. |
| Laser, sudden and full strength | You have been targeted | A reading likely exists; note the location for next time. |
This is why band callouts matter more than a single undifferentiated beep. McFlash announces the band aloud, so you can judge an alert without taking your eyes off the road. See the specs.
The false-alert problem
Why it is getting worse
Nearly every new car sold ships with 24 GHz blind-spot radar. In dense traffic your detector is surrounded by K-band emitters that did not exist a decade ago. A device with raw sensitivity and no filtering becomes unusable in town, and a detector you mute in town is a detector that does not warn you on the motorway either.
How filtering fixes it
- City mode cuts sensitivity to short-range K sources while leaving Ka at full reach.
- Signal-shape analysis discards the hard spike-and-vanish pattern of a door sensor.
- Band-specific muting lets you silence X entirely without losing Ka warnings.
- Volume ramping keeps weak distant alerts quiet and close ones loud.
Specs worth paying for
- Full Ka segment coverage with a fast sweep — the single highest-value spec.
- 360° antenna coverage, because rear and cross-street shots are common.
- Clear band identification, spoken rather than icon-only.
- Effective K-band filtering, judged by how often you want to mute it in town.
- Ignore: headline X-band claims, Ku support, and 'military grade' language with no numbers behind it.
Frequently asked questions
Which radar band do police use most?
Ka-band, specifically the 33.8, 34.7 and 35.5 GHz segments. It is the dominant enforcement band across the US and Canada, which is why Ka sensitivity is the most important spec on a detector.
Why does my detector alert on K-band all the time?
K-band at 24.15 GHz is shared with automatic supermarket doors, blind-spot monitoring radar in modern cars, and some traffic sensors. City mode reduces sensitivity to those short-range emitters.
Is X-band still worth having?
Barely. A handful of eastern US jurisdictions still run X-band, but most X alerts you hear are door sensors. It is a checkbox spec, not a buying reason.
What is Ku-band and do I need it?
Ku is 13.45 GHz and appears in parts of Europe. On North American roads it is effectively unused. It does no harm, but it should not influence your choice.
Is laser a radar band?
No. LIDAR uses 904 nm infrared pulses rather than microwave radio. Detectors use separate photodiodes for it, and because the beam is so narrow, a laser alert usually means you have already been measured.
What is VG-2 and Spectre detection?
They are radar-detector detectors: equipment that senses the local-oscillator emissions leaking from a detector. They only matter in jurisdictions where detectors are prohibited.
Do all detectors scan every Ka segment?
No. Cheaper units narrow their sweep to speed up response, which can miss segments. Full Ka coverage with fast sweep is the combination you want.
Does band matter outside North America?
Yes. European enforcement uses a different band mix, and many countries lean on cameras that emit nothing at all. Check the legality and enforcement guide for your country first.
Sources & how we check this
- Band allocations follow standard North American enforcement frequency assignments.
- Ka segment usage reflects the three segments in common patrol-gun deployment.
- K-band interference sources: automotive blind-spot radar and 24 GHz automatic door sensors.
Road law changes. We re-check every legality page each quarter, and this page was last reviewed in August 2026. Spotted something out of date? Tell us.
Keep reading
Get McFlash at 50% off today
Free worldwide shipping, 30-day money-back guarantee.
- Free worldwide shipping on every order
- 30-day money-back guarantee
- Encrypted card payment
Ships to 40+ countries · All prices are in USD and charged in USD.