Tools for the radio shack
Antenna calculators, live band conditions, satellite tracking, Morse code, licence exam practice, channel charts and electronics, worked out properly and explained in plain English. Free, no sign-up, and everything runs in your browser.
Propagation
- Fresnel zone calculatorFresnel zone radius, 60% clearance, earth bulge and radio horizon for a point-to-point link.
- Meteor shower calendarThe next meteor showers with rates, moonlight and radiant height for you, including daytime showers for meteor scatter.
- HF band conditionsLive solar flux, K-index, X-rays, solar wind and NOAA alerts, with a band-by-band estimate for day and night.
- NCDXF beacon trackerWhich of the 18 worldwide HF beacons is transmitting on each band right now, with headings and distances.
- Grey line map and UTC clockLive day, night and twilight map, your sunrise and sunset, and which DX locations share the grey line now.
Satellites
- Satellite Doppler calculatorHow much to retune on 2m and 70cm through a satellite pass, minute by minute.
- Dish antenna gain calculatorGain and beamwidth of any dish at any frequency, including QO-100, and the focal length from its depth.
- Moon tracker and EME plannerMoon direction now, moonrise and set, EME path loss and Doppler, and shared moon windows with a DX station.
- Live satellite tracker mapWhere the ISS and other satellites are now, with ground tracks, coverage and what's above you.
- ISS and satellite visible passesWhen you can see the ISS, Tiangong, Hubble and other bright satellites with your own eyes.
- Satellite dish alignment calculatorAzimuth, elevation and LNB skew for Astra, Hot Bird, DirecTV, DISH and Optus from your postcode.
- Satellite dish pointing calculator (USA)Compass heading, elevation and skew for DirecTV, DISH and free-to-air satellites from your ZIP code.
- Satellite dish alignment calculator (Australia)Bearing, elevation and LNB skew for Foxtel and VAST on Optus 156°E from your postcode.
- QO-100 calculatorDish pointing for the geostationary amateur satellite, and uplink, downlink and LNB IF conversion.
- Weather satellite pass predictorWhen the Meteor-M satellites pass over for 137 MHz pictures, with frequencies and an antenna calculator.
- GNSS sky viewGPS, Galileo, GLONASS and BeiDou satellites above you now, with usable count and PDOP.
- Amateur satellite pass predictorWhen the ISS and the ham satellites pass over you, how high they get, a sky plot and the frequencies to use.
On the air
- FT8 clock checkHow far your computer's clock is from UTC, to the millisecond, and whether it's good enough for FT8 and FT4.
- UTC time converterUTC now, UTC to local time and back for any date, and the same moment around the world.
- ADIF log viewer and converterOpen an ADIF log to count countries, bands and modes, find duplicates, and convert ADIF to CSV or back.
- QSL card designerDesign your QSL card with your details or photo, then download a 300 dpi image or print at 140 × 90 mm.
- Learn Morse code: trainerLearn CW by ear with the Koch method and Farnsworth timing, from two letters to all 40 characters.
- Morse code translator and decoderText to Morse and back, play or download it as audio, and decode Morse from a recording or your microphone.
- Repeater offset calculatorThe input frequency, offset and shift direction for any repeater in the UK, Europe, the US or Australia.
- APRS frequencies, SSIDs and passcodeAPRS frequency for every region, what each SSID is for, the right path, and an APRS-IS passcode generator.
- SSTV decoder and encoderTurn an SSTV recording into a picture, such as ISS images, or turn a picture into SSTV audio.
- Live POTA spotsParks on the Air activators on now, filtered by band and mode, with the distance and heading to each park.
- Contest calendarThe next 12 months of major HF and VHF contests in your time or UTC, with calendar downloads.
Licence exams
- UK Intermediate licence quizPractice questions for the UK Intermediate exam, with an explanation for every answer.
- UK Full licence quizPractice questions on the advanced theory in the UK Full licence exam, with explanations.
- Technician practice test (US)Every question in the 2026-2030 Technician pool, with full practice exams, study by subelement and a missed-question drill.
- General class practice test (US)The full 2023-2027 General pool as practice exams or by subelement, with your progress saved.
- Amateur Extra practice test (US)All 600 questions of the 2024-2028 Extra pool, with 50-question practice exams and the diagrams.
- Foundation licence practice quizPractice questions for the UK Foundation exam on every topic, with an explanation for each answer.
- Australian Foundation licence quizPractice questions for the Australian Foundation amateur licence, with an explanation for every answer.
Station and licence
- Battery C-rate calculatorConvert C-rate to amps for any battery, the C-rate of your current, and the run time.
- Harmonics and interference calculatorWhere your transmitter's harmonics land, such as FM, DAB, TV or mobile phones, and which bands could cause interference.
- Battery bank and solar calculatorBatteries in series and parallel, and the battery and solar panel size for an off-grid or portable station.
- EMF exposure calculatorWhether Ofcom's EMF condition means you need an assessment, and the safe distance from your antenna.
- Battery runtime calculatorHow long your battery will run your radio portable, for any chemistry, mode and transmit time.
- UK callsign decoderWhat a UK callsign tells you: licence level, region, club or special event, and what /P and /M mean.
Location
- Callsign prefix lookupWhich country any callsign is from, its CQ and ITU zones, and the beam heading, plus all 340 DXCC entities.
- Beam heading calculator and azimuthal mapShort and long path headings to any callsign, prefix, locator or country, on a world map centred on you.
- Maidenhead grid square locatorFind your QTH locator from GPS, convert locators to coordinates, and get distance and beam heading.
Antennas
- Yagi stacking calculatorOptimum stacking distance for two Yagis and a quarter-wave coax phasing harness to feed them.
- 5/8-wave vertical calculatorRadiator and radial lengths for a 5/8-wave vertical on any band, and how to match it.
- Folded dipole calculatorLength, impedance step-up and feed impedance of a folded dipole for equal or unequal conductors.
- HB9CV antenna calculatorElements, spacing, phasing line taps and matching capacitor for the two-element HB9CV beam.
- Beverage antenna calculatorLength, directivity, termination and feed transformer for a low-noise Beverage on 160m and 80m.
- OCF (Windom) dipole calculatorTotal and leg lengths for an off-centre-fed dipole, and which harmonic bands will match with a 4:1 or 6:1 balun.
- QFH antenna calculatorEvery dimension of a quadrifilar helix for 137 MHz weather satellites, corrected for conductor size and bends.
- Log periodic (LPDA) calculatorNumber of elements, every element length and spacing, and boom length for any frequency range.
- ADS-B 1090 MHz antenna calculatorCoaxial collinear and ground plane dimensions for flight tracking on 1090 MHz, or any other frequency.
- Discone antenna calculatorCone, disc and gap dimensions for a wideband discone for scanners and SDRs.
- Loading coil calculatorInductance and turns for a base or centre-loaded short vertical or mobile whip, with efficiency.
- Mast wind load and guying calculatorWind force on your antenna and mast, base bending moment, and guy length, tension and breaking strength.
- Dipole calculatorTotal and leg lengths for any frequency, every HF band at a glance, and a trim-to-resonance helper.
- EFHW and random wire calculatorEnd-fed half-wave length and harmonic bands, plus random wire lengths that keep a 9:1 unun happy.
- J-pole and Slim Jim calculatorEvery dimension for a 2m or 70cm J-pole or Slim Jim, in pipe, wire or ladder line, with a diagram.
- Horizontal loop (sky loop) calculatorWire and side lengths for a full-wave horizontal loop in any shape, and the bands it covers.
- Inverted L calculatorVertical and horizontal lengths for a 160m or 80m inverted L at your mast height, with radials.
- Helical antenna calculatorDiameter, spacing, gain and matching for an axial-mode helix for satellites and QO-100.
- Antenna height and take-off angleHow height shapes a dipole or beam's vertical pattern, with the main lobe angle and skip distance.
- Yagi antenna calculatorElement lengths and spacings for 3 to 17 element Yagis from the tested NBS designs, for any band.
- Quarter-wave vertical and ground plane calculatorVertical and radial lengths for any band, elevated or on the ground, and how many radials are worth laying.
- Magnetic loop calculatorEfficiency, tuning capacitor, bandwidth and capacitor voltage for a small transmitting loop on every band.
- G5RV and ZS6BKW calculatorG5RV, half-size G5RV and ZS6BKW dimensions, with the matching section cut for your ladder line.
- Trap and fan dipole calculatorTrap values and wire lengths for a two-band trap dipole, and element lengths for a fan dipole.
- Moxon, delta loop and quad calculatorDimensions for a Moxon rectangle with wire-size correction, a full-wave delta loop and a two-element quad.
Feedline and matching
- Wilkinson splitter calculatorLine impedance, length and isolation resistor for a Wilkinson splitter or combiner, including lumped and N-way designs.
- PEP, RMS and average power calculatorPEP from oscilloscope volts, RMS and peak voltage and current, and average power for every mode.
- Smith chart and matching calculatorPlot any load on a Smith chart, with SWR, single-stub matching, hairpin match values and gamma match starting points.
- Unun calculatorTurns and core for a 49:1, 64:1, 9:1 or 4:1 unun, a check for your lowest band, and the SWR to expect.
- Coax and twin-line impedance calculatorImpedance, velocity factor and capacitance from cable dimensions, and the size for a target impedance.
- Coax stub and velocity factor calculatorQuarter-wave stubs to notch harmonics, electrical length of any cable, measured velocity factor and Q-section matching.
- Choke and balun calculatorFerrite mix, core and turns for a common-mode choke, plus what a coil of coax does on each band.
- Coax loss calculatorLoss for any cable, length and frequency, including SWR, with every common cable compared.
- SWR calculatorSWR from forward and reflected power, and conversions between VSWR, return loss and reflection coefficient.
- dBm, watts and ERP calculatorConvert power units, work out ERP and EIRP, and check against UK licence limits and Ofcom's EMF threshold.
RF and electronics
- Microstrip impedance calculatorPCB track width for 50 Ω on FR-4, Rogers or PTFE, or the impedance of any track.
- Bandpass filter calculatorLC Butterworth and Chebyshev bandpass filters for any centre frequency and bandwidth, with a response plot.
- Image frequency calculatorLocal oscillator and image frequency of a superhet receiver for any IF, and what the image lands on.
- Pi network calculatorPlate load, tune and load capacitors and coil for a valve amplifier's tank circuit on every HF band.
- Decibel calculatordB to power and voltage ratios and back, and adding up gains, losses and noise in dB.
- S-meter converterS-units to dBm, microvolts and dBµV and back, using the standard S9 = −73 dBm on HF and −93 dBm on VHF.
- Noise figure calculatorCascaded noise figure of LNAs, coax and receivers, with noise temperature, noise floor and sensitivity.
- Low-pass filter and L-network calculatorChebyshev and Butterworth harmonic filters with toroid turns, and L-network matching for any load.
- RF attenuator calculatorPi and T pad resistor values for any attenuation, with the power each resistor must handle.
- Wire gauge calculator (AWG to mm²)SWG, AWG and mm with resistance, weight, current and RF resistance from skin effect.
- Frequency to wavelength calculatorFrequency to wavelength and back, with half, quarter and 5/8 wave lengths and a velocity factor option.
- Toroid and coil calculatorTurns on Amidon iron powder and ferrite toroids, air-core coil inductance, and LC resonance.
- Path loss and link budget calculatorFree space path loss, received signal and S-meter reading, dBi and dBd, and the radio horizon.
Electronics
- Watts, volts and amps calculatorConvert watts, volts and amps for DC, single-phase and three-phase, with running cost and plug fuse.
- Buck and boost converter calculatorDuty cycle, inductor and output capacitor for a step-down or step-up switching regulator.
- Inductor colour code calculatorRead the coloured bands on moulded inductors and RF chokes, in microhenries.
- Capacitors and inductors in series and parallelTotal capacitance or inductance of any number of parts in series or parallel.
- PCB trace width calculatorIPC-2221 track width for any current and temperature rise, with resistance and voltage drop.
- LM317 calculatorResistors for any LM317 output voltage, the regulator's heat, and the resistor for a constant-current source.
- Zener diode regulator calculatorSeries resistor and power ratings for a zener voltage regulator over your input voltage range.
- RC time constant and filter calculatorTime constant, charging curve and capacitor voltage at any time, and RC filter cutoff frequency.
- Op-amp gain calculatorInverting and non-inverting gain, bandwidth from GBW, and the best standard resistors for any gain.
- Transformer turns ratio calculatorSecondary voltage, current and impedance from the turns ratio, for mains, audio and RF transformers.
- Heatsink calculatorThe heatsink thermal resistance needed to keep a regulator or transistor cool, for TO-220, TO-247 and TO-3.
- LED resistor calculatorThe series resistor for one LED or a string, with the nearest standard value and the wattage you need.
- Voltage divider calculatorDivider output with a load, and the best pairs of standard resistors for any input and output voltage.
- 555 timer calculatorAstable frequency, duty cycle and timing, and monostable pulse length, with a waveform preview.
- LC resonance and reactance calculatorResonant frequency from L and C, or the L or C you need, plus reactance at any frequency.
- SMD resistor and capacitor codesDecode 3-digit, 4-digit and EIA-96 resistor codes and capacitor codes, or find the code for a value.
- DC cable voltage drop calculatorVoltage lost in 12 V and 24 V cables, and the smallest mm² or AWG wire for radios, cars, solar and boats.
- Ohm's law calculatorVoltage, current, resistance and power from any two, plus dividers, series and parallel, and LED resistors.
- Resistor color code calculatorRead 4, 5 and 6 band resistors, find the colours for any value, and the nearest standard values.
Channels
- CB radio channelsUK FM, EU and US 27 MHz CB channels, and the 80 Australian UHF CB channels, with emergency and calling channels.
- PMR446, FRS and GMRS channelsFrequencies for every walkie-talkie channel in Europe and the US, power limits and the 38 privacy codes.
- Marine VHF channelsEvery international marine channel with ship and coast frequencies and its use, plus AIS and UK marina channels.
- 8.33 kHz airband channel calculatorConvert aviation channel names such as 118.005 to the real frequency and back, and list any block of channels.
Reference
- Ham radio abbreviationsWhat 73, 88, QSL, OM, XYL, FB and the common CW shorthand and prosigns mean, searchable.
- UK HF band planEvery RSGB band plan segment from 160m to 10m, including the 60m UK segments, with a frequency lookup.
- European HF band planThe IARU Region 1 band plan used across Europe, from 160m to 10m, with a frequency lookup.
- US ham radio band planARRL band plan and FCC privileges for Technician, General and Extra on every HF band.
- Australian amateur band planWIA HF band plan with Foundation, Standard and Advanced licence access for each band.
- European VHF and UHF band planIARU Region 1 plan for 6m, 2m and 70cm: calling channels, repeaters, beacons and satellites.
- Australian VHF and UHF band planWIA plan for 6m, 2m and 70cm with repeater blocks, offsets, calling frequencies and licence access.
- Digital mode frequenciesFT8, FT4, WSPR, JS8Call, PSK31, RTTY and SSTV frequencies on every band from 160m to 70cm.
- CTCSS tones and DTMF generatorAll 50 CTCSS tones with UK repeater codes A to J, a 1750 Hz toneburst and a DTMF keypad.
- 2m and 70cm band plansUK (RSGB) and US (ARRL) band plans with calling frequencies, repeater channels and offsets, searchable.
- Q codes and RST reportsEvery common Q code with its question and answer meaning, searchable, plus the RST scale.
- NATO phonetic alphabetNATO and ITU phonetics with pronunciation and Morse, and a speller for your callsign.
Built for people who actually build things
ShackWiki has over 120 free tools for amateur radio and electronics: antenna and feedline calculators, live band conditions and satellite tracking, licence exam practice for the UK, US and Australia, Morse code training, channel charts for CB, PMR446 and marine radio, and everyday electronics calculators.
Every tool explains its working. You get the formula, a diagram on most calculators that redraws as you change the numbers, and the practical advice that usually lives in forum threads: cut it long, fold the spare back, choke the feedline, check the power rating of that unun before you run FT8 through it.
Lengths are given in metres and in feet and inches, and band plans cover the UK and Europe, the US and Canada, and Australia. Everything runs in your browser, with no sign-up and nothing to install.