From the air to the app

How scanner audio is made

ThinLine Radio does not generate radio traffic. An operator puts up an antenna, digitizes the signal with an SDR, decodes it with software they chose, and only then does audio reach a server they run. This page is the chain, the programs, what it usually costs — and why that audio should stay yours.

1 Antenna RF in the air. Discone, yagi, mag-mount, or a mast on a roof.
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2 SDR tuner USB stick or Airspy turns radio into I/Q samples the computer can read.
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3 Decoder SDRTrunk, Trunk Recorder, and others demodulate P25, analog FM, DMR, NXDN.
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4 Call files Each transmission becomes audio plus talkgroup, radio ID, and time.
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5 ThinLine Radio Ingest, delay, accounts, alerts. Same family of API as Rdio Scanner.
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6 Listeners Web player, iOS, and Android. The app is a client. It is not the radio.

Generated illustration of a rooftop wideband scanner antenna on a short mast — Audio starts in the air. A wideband antenna on a mast, with coax to the radio, is the first piece of a feed — not the app store listing. Generated illustration. Not a photograph of a specific antenna or installation.

Generated illustration of generic USB software-defined radio dongles next to a small computer — Operators typically use USB SDR tuners into a hub or a small PC. Digital trunking often wants more than one receiver. Generated illustration. Not Nooelec, RTL-SDR Blog, Airspy, or any other branded product photo.

Generated illustration of a generic trunking-decoder screen with a talkgroup list and waterfall — Decoder software watches the control channel, follows voice frequencies, and writes one audio file per call. ThinLine Radio is not this program. Generated illustration. Not a screenshot of SDRTrunk, Trunk Recorder, DSDPlus, or any other decoder.

What ThinLine Radio is in this chain

Steps 1–4 belong to the operator. They buy the antenna and the tuners, they pick the decoder, they decide what talkgroups get recorded and how long audio is delayed. ThinLine Radio is the platform that receives those files, stores them, applies the delay the operator configured, and serves the web player and the mobile apps.

That is why a quiet county in the app is almost never “the app broke.” It is an antenna, a dongle, a computer that went to sleep, or an operator who stopped the recorder.

Once those files exist, you choose where they go. Keep them on a server you run — or hand them to a third-party network that did not pay for the roof. Run yours is that choice.

The programs that actually hear the radio

ThinLine Radio is compatible with the same recorder-side world Rdio Scanner used: software that can drop one audio file per conversation. We did not write SDRTrunk or Trunk Recorder. Those projects, and the people who maintain them, are why any of this works.

SDRTrunk

Dennis Sheirer

Java trunking decoder used by a lot of P25 and multi-protocol hobby sites. Follows the control channel, records calls, talks to the same ingest style ThinLine Radio expects.

github.com/DSheirer/sdrtrunk

Trunk Recorder

Luke Berndt

Open-source recorder built around GNU Radio. Common on Raspberry Pi and small Linux boxes. Writes per-call audio that operators point at ThinLine Radio or Rdio Scanner.

github.com/robotastic/trunk-recorder

RTLSDR-Airband

Tomasz Lemiech and contributors

Lightweight multi-channel AM/NFM receiver. Often used for airband and analog public-safety channels rather than full digital trunking.

github.com/szpajder/RTLSDR-Airband

DSDPlus Fast Lane

DSDPlus LLC

Windows digital-voice decoder (P25, DMR, NXDN, and others). Many operators pair it with a tuner front-end, then feed completed calls into the scanner server.

dsdplus.com

ProScan

Windows scanner control and recording. Used when the radio is a traditional scanner deck rather than a pile of USB dongles.

proscan.org

voxcall

Community / hobby recorder

Call-oriented recorder in the same ingest family: audio files split by transmission, which is what ThinLine Radio needs to index a feed.

rtl-sdr / osmocom USB stack and GNU Radio sit under several of these tools. If you run Linux dongles, you are standing on that work too.

Generated illustration of a small always-on PC on a shelf with USB radio dongles and Ethernet — A “server” for a county feed is usually this: a small PC that never sleeps, USB tuners, Ethernet, and coax to the roof. Not a datacenter rack. Generated illustration. Not a photo of a specific PC, tuner brand, or operator site.

What people actually spend

Street prices in US dollars, 2026 ballpark. This is not a store and we do not sell hardware. Operators shop RTL-SDR Blog, Airspy, Amazon, and ham swap meets. Electricity is the quiet monthly bill.

Starter analog

About $150–$350

RTL-SDR class dongle$35–$45
Mag-mount or small discone$25–$80
Used PC or Raspberry Pi 5$80–$220
Coax, adapters, USB cable$20–$40

Enough for a few analog channels. Not a full P25 trunked system.

Typical county feed

About $500–$1,200

2–4 dongles or an Airspy$80–$250
Roof antenna, mast, coax, ground$150–$400
Mini PC (N100 class), always on$200–$400
Optional LNA / band-pass filter$40–$120

This is the box behind most independent ThinLine Radio / Rdio Scanner sites you hear in the app.

Monthly / extras

Usually $5–$25 / mo

Electricity, always-on PC$3–$15
Optional VPS if not at home$5–$20
Domain name~$12 / yr
ThinLine Radio softwareYou host it

You do not need our cluster to run a feed. The HA nodes on the Status page are ThinLine’s public services, not your garage PC.

Scanning laws differ by country and state. This page is how the audio chain works, not legal advice. Encrypted systems are not something we help decode.

Your antenna. Your server.

Stop uploading your audio to someone else’s business

You paid for the mast, the tuners, the always-on PC, and the hours. Piping that into a third-party feed network means they keep the listeners, the ads, and the income. You keep the electric bill. They did not buy the setup. They still make a product out of it.

Run ThinLine Radio on hardware you control. Charge for access if that is the model. Stay a free public service if that is the model. Expand to another county when you are ready. Offer delay, accounts, alerts, and a real app — not a slot on a national feed page.

Run your own server

The files stay on a machine you own or rent. You set the delay, the users, and who hears what. Nobody else gets to rebrand your county as their inventory.

Generate income

Accounts and billing are in the software. Subscriptions, access groups, commercial sites — if you want to recoup the hardware, you can. If you want it free for the county, that is still your call.

Expand

Add talkgroups, add a second site, add another operator. You are not waiting for a directory to give you a slot or a national network to notice the feed.

Offer a better service

Transcription, tone alerts, incident maps, iOS and Android. That is what listeners actually stay for — not a generic player on somebody else’s domain.

This is not a promise that a feed will pay for itself. Most hobby sites never will, and that is fine. The point is the audio, the listeners, and the rules stay with the person who put up the antenna. See platform features.

Credit where it belongs

ThinLine Radio sits at the end of a long chain of people who published tools for free or for a modest license. We extend Rdio Scanner. We do not pretend we invented SDR, P25 decoding, or USB tuners.

Project	People / org	Role in the chain
SDRTrunk	Dennis Sheirer	Digital trunking decoder
Trunk Recorder	Luke Berndt	GNU Radio recorder
RTLSDR-Airband	Tomasz Lemiech & contributors	Analog / airband receive
DSDPlus Fast Lane	DSDPlus LLC	Digital voice decode
ProScan	ProScan	Scanner control & record
rtl-sdr / osmocom	osmocom & contributors	USB dongle stack
GNU Radio	GNU Radio project	SDR signal processing
Rdio Scanner	Chrystian Huot	Scanner server ThinLine is built on
ThinLine Radio	ThinLine Dynamic Solutions	Platform, apps, delay, accounts, alerts

Project names and marks belong to their authors. Links go to the upstream sites. If we missed a recorder you use with ThinLine Radio, tell us on Discord.