Ham Radio

Ham Radio Protocols

Your comprehensive guide to radio frequencies, protocols, and the tools to explore them.

GMRS (General Mobile Radio Service)

Frequency allocation: 462-467 MHz, 22 channels total. Channels 1-7 and 15-22 allow up to 50W, channels 8-14 limited to 5W.

Repeater pairs: Channels 15-22 use +5 MHz offset (input 467.550-467.725, output 462.550-762.725).

Licensing: $35 FCC registration, no examination required, 10-year term covers immediate family.

CTCSS/DCS: Privacy codes prevent interference but don’t provide security - all transmissions remain receivable.

Amateur Radio Fundamentals

2 meters (144-148 MHz): Most popular VHF band. Repeater outputs 144-145 MHz, inputs 145-146 MHz with +600 kHz offset. Simplex operation on 146.52 MHz (national calling frequency).

70 centimeters (420-450 MHz): UHF band with +5 MHz offset for repeaters. Regional variations exist - West Coast often uses -5 MHz.

6 meters (50-54 MHz): “Magic band” with sporadic E propagation enabling 500+ mile contacts during openings.

License progression: Technician (VHF/UHF privileges, limited HF), General (most HF bands), Amateur Extra (full privileges including exclusive subbands).

Exam structure: 35 multiple choice questions, 74% passing score. No Morse code requirement since 2007.

Mesh Networking

Meshtastic: LoRa modulation on 915 MHz (US), 868 MHz (EU), 433 MHz (Asia). Spreading factors SF7-SF12, higher SF = longer range but slower data rate. AES-256 encryption with rotating keys.

Hardware: ESP32-based nodes, typical 1-10km range depending on terrain and antenna height.

Protocols: Position sharing, text messaging, sensor data relay through multi-hop mesh.

AREDN (Amateur Radio Emergency Data Network): High-speed mesh on 2.4/5.8 GHz using modified OpenWrt firmware. IP networking over amateur frequencies enables video, VoIP, file sharing.

Equipment: Ubiquiti devices flashed with AREDN firmware. Bandwidth up to 150 Mbps depending on modulation and channel width.

ATAK Integration

TAK (Team Awareness Kit): Military-derived situational awareness platform using Cursor-on-Target (CoT) messages in XML format.

Data sources: GPS positions, imagery, chat, file sharing.

Radio integration: APRS position feeds, voice coordination on amateur frequencies.

Mesh compatibility: Operates over any IP network including AREDN mesh nodes.

Plugin architecture: Supports various radios through TAK server or direct integration. Amateur radio provides backup when primary data links fail.

Software Defined Radio

HackRF One: 1 MHz - 6 GHz coverage, half-duplex operation. Sample rate up to 20 MSPS, 8-bit resolution.

Software: GNU Radio, SDR#, GQRX, Universal Radio Hacker.

Applications: Spectrum analysis, signal reverse engineering, protocol development, interference hunting.

RTL-SDR: $20-30 dongles covering 24-1700 MHz (with gaps). RTL2832U + R820T2 common chipset combination.

Uses: ADS-B aircraft tracking, ACARS decoding, trunked radio monitoring, ISM band analysis.

Flipper Zero Capabilities

Sub-GHz radio: 300-928 MHz coverage using CC1101 transceiver. ASK, FSK, GFSK, MSK modulations with configurable parameters.

Applications: Garage door analysis, weather station monitoring, ISM device research.

Storage: Raw recordings and protocol analysis for reverse engineering.

Additional radios: 125 kHz RFID, 13.56 MHz NFC, infrared transceiver.

GPIO interface: External radio modules and sensors. Open source firmware with active development community.

ADS-B Surveillance

Frequency: 1090 MHz, Mode S transponders broadcasting position, velocity, identification, status.

Range: Line-of-sight, typically 100-250 miles with elevated antenna.

Decoding: dump1090 software with RTL-SDR hardware.

Integration: Feeds to FlightRadar24, ADSBexchange for global tracking network.

Military/sensitive aircraft: Often operate with transponders disabled or on different frequencies.

MLAT: Multilateration using time-difference-of-arrival from multiple receivers enables tracking without GPS broadcasts.

Programming Procedures

TH-D3 offset programming: Menu → Frequency → Offset Direction (+ or -) → Offset Frequency → Enter value → Store.

Memory channels: Menu → Memory → Channel number → Store current frequency/settings.

CTCSS: Menu → Signaling → CTCSS → Tone frequency selection.

Repeater directories: RepeaterBook.com, RadioLabs.com for frequency coordination.

Band plans: ARRL band plan documents specify recommended uses for frequency segments.