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Amateur radio and RF knowledge

Short, technically checked explanations of the Signal-Pirat tools. Each page leads straight to the matching calculator, decoder or trainer in the browser.

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Learning and exam

• Exam trainer for the amateur radio exam in Austria

  Prepare for the amateur radio exam in Austria: exam trainer with 69 questions and explanations, timed mock exam, learning paths and exercises – free.

• Learn amateur radio – step by step

  Learn amateur radio from scratch: learning paths from basics to antennas and digital modes, exercises with worked solutions, calculators and animations – free.

• Radio in motion – radio technology as animation

  Radio technology made visible: animations of waves, propagation, standing waves, Yagi directivity, the Smith chart and AM/FM spectrum – interactive.

• Formula collection for radio and RF engineering

  Formula collection for amateur radio and RF: Ohm's law, wavelength, decibels, resonant circuits, antennas, lines and propagation – with calculators.

• Radio engineering exercises with worked solutions

  68 radio engineering exercises with full worked solutions: electronics, antennas, propagation, modulation and decoders – to recalculate in the browser.

Decoders and signals

• Morse decoder and CW practice audio in the browser

  Morse decoder in the browser: decode CW from a recording or live via microphone, play text as Morse and save it as WAV, with Farnsworth timing for learning.

• APRS decoder for 144.800 MHz in the browser

  Decode APRS packets from a recording or live from the receiver: AFSK 1200 Bd, AX.25 with checksum, position, message, status and telemetry.

• RTTY decoder for radio teletype

  Decode RTTY in the browser: ITA2, 45.45 Bd, 170 Hz shift, automatic mark tone, squelch, from a recording or live – and create practice audio.

• PSK31 decoder in the browser

  Decode PSK31 and PSK63 in the browser: BPSK from a recording or live, carrier detected and tracked, Varicode after G3PLX, practice audio as WAV.

• Signal search with waterfall and mode detection

  Waterfall in the browser: find signals in a recording or live and identify the mode – CW, RTTY, PSK31/63, QPSK31 and APRS are decoded straight away.

• Receiving and tracking radiosondes

  Receive weather sondes in 400.15–406 MHz with an SDR: radiosonde_auto_rx and SondeHub, range by sonde altitude, what to do with landed sondes.

Calculators and antennas

• Radio horizon calculator for VHF and above

  Calculate radio horizon and line of sight: range from both antenna heights with earth curvature and k = 4/3, plus free-space loss and link budget.

• Fresnel zone and terrain profile

  Calculate the Fresnel zone and terrain profile: radius along the link, clearance over obstacles and earth curvature – for links, repeaters and LoRa.

• LoRa calculator: airtime, duty cycle and range

  LoRa calculator for 868 MHz: airtime per packet, duty cycle, sensitivity by spreading factor and bandwidth, range and link budget.

• Dipole calculator and antenna lengths

  Calculate dipole length: half-wave dipole for HF, 2 m and 70 cm with velocity factor, plus wavelength, quarter-wave radiator and matching.

• Antenna simulation in the browser

  Simulate antennas in the browser: radiation pattern, gain, impedance and SWR for dipole, ground plane and Yagi – no installation, with terrain influence.

• SWR calculator and RF tools

  RF calculators in the browser: SWR, reflection coefficient, return loss, dBm and watts, cable loss, wavelength, resonant circuit – with worked steps.

• Interactive Smith chart

  Understand the Smith chart interactively: see impedance, reflection coefficient and SWR, follow line transformation and calculate L-network matching.

• LoRa mesh planner: nodes, links, hops

  Plan a mesh network in the browser: links between node pairs, radio horizon, Fresnel zone, hops and bottlenecks for Meshtastic, MeshCore and MeshCom.

• S-meter calculator: S-units, dBm and microvolts

  Convert S-meter readings per IARU Region 1: S9 = −73 dBm on HF, −93 dBm on VHF, 6 dB per S-unit – with table and a check of your own S-meter.

• HAMNET and link planner for point-to-point links

  HAMNET in Austria: IP data network of radio amateurs on amateur bands. Plan a link with margin, Fresnel zone, earth bulge and radio horizon.

• Design a microwave horn antenna and make it by 3D printing

  Design an optimum-gain pyramidal horn for amateur microwave bands: aperture, length, beamwidth, waveguide WR-90 to WR-4, metallisation and STL file.

Propagation and sky

• Tropospheric radio weather and extended range

  Understand tropo radio weather: refractivity, inversions and ducting, extended range on 2 m and 70 cm – with calculator and explanations.

• HF propagation and space weather

  Understand HF propagation: ionosphere, MUF, daily and seasonal variation, solar activity, K-index and aurora – which band works when.

• Satellite passes and ground station

  Predict passes of the ISS and amateur radio satellites: time, elevation, direction and Doppler shift from orbital data – with frequencies and ground station.

Operating practice

• Repeater list Austria with map and CHIRP export

  Amateur radio repeaters in Austria on a map: frequency, offset, CTCSS and mode, filterable by band – and as a CHIRP file for your radio.

• Radiotelephony trainer for amateur radio

  Practise radiotelephony: international phonetic alphabet, Q codes, procedure words and the flow of a radio contact – with listening and speaking exercises.

• Radio logbook with ADIF import and export

  Amateur radio logbook in the browser: log contacts in UTC, import and export ADIF, optionally sync with your account – plus operating aids.

• Radio services at a glance

  Which radio for what? Overview of PMR446, CB radio, LoRa, amateur radio and other services – with frequencies, limits and licence requirements.

• Radio control with CAT and PTT in the browser

  Control your radio via USB in the browser: frequency, mode and transmit key for Icom CI-V, Kenwood and Yaesu – with transmit guard and virtual radio.

• Emergency and disaster radio in Austria

  Emergency radio for amateurs in Austria: legal framework under TKG 2021, emergency frequencies with sources, operating principles, radio log, message form.

• Self-sufficient radio station: power need, battery and solar panel

  Plan a radio station without mains or internet: Meshtastic node, radio, mini PC with local AI – calculate daily need, battery runtime and solar panel.

• FPV channels at 5.8 GHz: table, law and video link

  FPV channel table Raceband and bands A, B, E, F with legal status per channel: licence-exempt 5725–5875 MHz up to 25 mW EIRP, otherwise amateur only.

Building

• Build guide: receiving station for ADS-B and AIS

  Build guide for a receiving station: receive aircraft on 1090 MHz (ADS-B) and ships on 162 MHz (AIS) with an SDR stick – parts, antennas, legal notes.