Best Police Scanner for Illinois: Frequencies, Systems & Recommendations
Best Police Scanner for Illinois: Frequencies, Systems & Recommendations
Illinois is one of the more layered states to scan. Statewide agencies run on STARCOM21, a single Project 25 trunked network that stretches from Rockford to Cairo, while Chicago and Cook County run their own separate systems entirely. Add in the fact that Chicago PD has fully encrypted its dispatch traffic since 2024, and picking the right scanner for Illinois comes down to knowing exactly what you can still hear before you buy.
This guide breaks down the state's radio systems county by county, tells you honestly where encryption blocks you out, and recommends the Uniden SDS150 or SDS100 depending on your budget and location.
Quick answer: If you live near Chicago or want the widest coverage across STARCOM21 sites statewide, get the SDS150. Its True I/Q platform handles Illinois' simulcast towers far better than older scanners. Budget-conscious buyers outside Chicago can do very well with the SDS100, which uses the same core decoding engine.
Illinois' Statewide System: STARCOM21
STARCOM21 (STAte Radio COMmunications for the 21st Century) is Illinois' statewide public safety network, owned and operated by Motorola Solutions in partnership with the Illinois State Police and the Illinois Emergency Management Agency. It is a 700/800 MHz, P25-compliant, digital trunked system with more than 270 tower sites and upwards of 36,000 subscribers, ranging from the Illinois State Police to county sheriffs, municipal departments, and state agencies.
If you only remember one talking point about scanning Illinois, make it this: the Illinois State Police use STARCOM21 as their primary statewide network, with VHF reserved as a backup in a handful of districts. Many county sheriffs and smaller municipal agencies have also migrated onto STARCOM21 talkgroups rather than maintain their own conventional systems, which is why a P25-capable scanner is non-negotiable for Illinois, not optional.
Some STARCOM21 talkgroups run P25 Phase II with TDMA modulation, which requires a Phase II capable scanner. Both the SDS150 and SDS100 handle Phase I and Phase II without any add-on modules.
Chicago and Cook County: A Different System, and Now Encrypted
Chicago does not run on STARCOM21. The city operates its own 800 MHz P25 Phase II trunked system managed by the Office of Emergency Management and Communications (OEMC). This matters because Chicago Police Department dispatch across all 22 police districts has been fully encrypted since 2024, following a phased rollout that started in 2022 under a program the city said was aimed at officer safety and protecting victim and witness identities.
That means a scanner, no matter how capable, will not pull in live Chicago PD dispatch audio. No consumer scanner can decode fully encrypted P25 traffic, and that includes the SDS150 and SDS100. What is still open in Cook County:
- Chicago Fire Department and EMS remain unencrypted on the OEMC 800 MHz system and are actively used as the primary dispatch method for fire and medical calls.
- Suburban Cook County departments vary agency by agency. Many smaller municipalities outside the city limits still run in the clear, either on STARCOM21 or their own conventional VHF/UHF channels.
- Mutual aid and MABAS fireground talkgroups stay open across the region even where individual departments have encrypted their primary dispatch.
If real-time Chicago PD audio is the main reason you are buying a scanner, set that expectation now. If you want fire, EMS, and the wider Illinois picture, a scanner is still very much worth owning.
County Snapshot
| County / Area | Primary System | Status |
| Cook (Chicago PD) | OEMC 800 MHz P25 | Encrypted |
| Cook (Fire/EMS) | OEMC 800 MHz P25 | Clear |
| Winnebago (Rockford) | STARCOM21 | Mostly clear |
| Sangamon (Springfield) | STARCOM21 | Mostly clear |
| Peoria | STARCOM21 / local VHF | Mostly clear |
| DuPage | DU-COMM / STARCOM21 | Mixed |
| Lake | STARCOM21 (simulcast) | Mostly clear |
| Madison / St. Clair | STARCOM21 | Mostly clear |
Encryption status changes as agencies upgrade equipment. Check RadioReference.com for your specific county before buying if encryption is a dealbreaker for you.
Why Simulcast Matters in Illinois
Several STARCOM21 sites, including coverage around Lake County, run in simulcast, meaning multiple towers broadcast the same talkgroup at once. Older digital scanners can struggle with the audio distortion this causes when you are positioned between towers. This is the exact problem Uniden's True I/Q platform in the SDS150 and SDS100 was built to solve, which is why both models are the ones we recommend for Illinois over older Uniden digital handhelds.
Recommended Scanners for Illinois
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Uniden SDS150 Best for Chicago-area and simulcast-heavy counties. True I/Q platform, built-in GPS, USB-C, and a larger color display for tracking STARCOM21 sites in real time. Shop the SDS150 |
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Uniden SDS100 Same True I/Q decoding core as the SDS150 at a lower price point. A strong choice for downstate Illinois counties outside the heaviest simulcast zones. Shop the SDS100 |
Watch: Setting Up Your Scanner
Our team walks through setup and programming on the Zip Scanners YouTube channel, including Sentinel software basics and simulcast troubleshooting that applies directly to Illinois listeners.
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Programming Your Scanner for Illinois
- Enter your zip code or let the built-in GPS on the SDS150 locate you automatically.
- Load the STARCOM21 statewide system plus your county's local sites from the preloaded USA database.
- If you are in a simulcast zone (Lake County, parts of Cook), enable the True I/Q simulcast handling rather than switching sites manually.
- Use Uniden Sentinel software to save a Favorites List for STARCOM21 alongside any local VHF/UHF fire and EMS channels.
- Skip programming entirely by adding Zip Scanners Expert Programming at checkout. We will research your county and ship the scanner ready to scan.
Further Reading and Research
For the most current talkgroup lists and site-by-site encryption notes, these RadioReference resources are kept up to date by local listeners:
- STARCOM21 Statewide Illinois Wiki, site lists and subscriber details
- STARCOM21 Talkgroups Database, searchable by county
- RadioReference Forums, active discussion threads on Illinois scanning and gear
Frequently Asked Questions
Can I listen to Chicago Police Department on a scanner?
No. All 22 Chicago PD districts moved to full P25 encryption by 2024. No consumer scanner can decode encrypted talkgroups. Chicago Fire and EMS remain unencrypted.
Do I need a P25 scanner for Illinois?
Yes. STARCOM21, the statewide system used by the Illinois State Police and many county agencies, is a P25 digital trunked network. An analog-only scanner will not decode it.
SDS150 or SDS100 for Illinois?
Both decode STARCOM21 equally well. Choose the SDS150 if you want built-in GPS and want to spend more time near Chicago's simulcast-heavy suburbs. The SDS100 is the better value pick for most downstate counties.
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Not sure which scanner fits your county? Book a free call with a Zip Scanners expert. We will look at your exact location and tell you what will and will not come through clear. Book a Meeting |
