#frequency

Doppler-effect maths as an API, computed locally and deterministically. The sound endpoint computes the acoustic Doppler shift, f' = f·(v + vo) / (v − vs), where v is the speed of sound (given directly, derived from an air temperature, or the default 343 m/s at 20 °C), vs is the source velocity and vo the observer velocity, with positive velocities meaning approaching: it returns the observed frequency and the frequency shift, and refuses a supersonic source. The light endpoint computes the relativistic Doppler effect for light, f' = f·√((1+β)/(1−β)), from a velocity in metres per second or as a fraction of the speed of light and a direction (approaching blue-shifts, receding red-shifts), returning the frequency and wavelength factor, the observed frequency or wavelength, and the redshift z. The radial-velocity endpoint reverses it: from a measured redshift, or an observed and rest wavelength, it recovers the radial velocity with the exact relativistic relation and the simple v ≈ z·c estimate. Frequencies are in hertz, wavelengths in nanometres, velocities in metres per second. Everything is computed locally and deterministically, so it is instant and private. Ideal for physics and astronomy education, radar, sonar and lidar tools, audio and acoustics apps, and spectroscopy and redshift calculators. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the Doppler effect; for sound levels and decibels use an acoustics API.

api.oanor.com/doppler-api

Wi-Fi channel maths as an API, computed locally and deterministically from the standard channel-numbering formulas. The channel endpoint returns the centre frequency of a Wi-Fi channel on the 2.4, 5 or 6 GHz band — the band is auto-detected from the channel number or can be given explicitly (2.4 GHz: 2407 + 5·channel, with channel 14 at 2484; 5 GHz: 5000 + 5·channel; 6 GHz: 5950 + 5·channel). The frequency endpoint does the reverse, returning the nearest channel and band for a centre frequency in MHz or GHz. The overlap endpoint reports whether two channels overlap at a chosen channel width (two channels overlap when their centre-frequency separation is less than the width) and gives the recommended non-overlapping set — the classic 1, 6 and 11 on 2.4 GHz at 20 MHz. Everything is computed locally and deterministically, so it is instant and private. Channel availability is regulated and varies by country. Ideal for networking and Wi-Fi tools, site-survey and IoT apps, and router and access-point configuration software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is Wi-Fi channel mapping; for general wavelength/frequency and photon energy use a wavelength API.

api.oanor.com/wifichannel-api

Antenna length maths as an API, computed locally and deterministically. The dipole endpoint gives the total and per-leg length of a half-wave dipole for a frequency, in metres, feet, inches and centimetres, applying a velocity factor (about 0.95 for wire) and also reporting the classic 468 ÷ f(MHz) feet rule of thumb. The quarterwave endpoint gives the element length of a quarter-wave vertical or monopole, with the 234 ÷ f(MHz) rule. The element endpoint computes the length of an element at any fraction of a wavelength — full-wave, half-wave, quarter-wave, fifth-wave, five-eighths or a custom fraction. Frequencies accept Hz, kHz, MHz and GHz, and the velocity factor is configurable. Everything is computed locally and deterministically, so it is instant and private. These are starting lengths: real antennas need trimming and tuning for the lowest SWR, as end effects and surroundings shift the resonant length. Ideal for amateur-radio and RF tools, antenna and IoT design, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is antenna geometry; for general wavelength, frequency and photon energy use a wavelength API.

api.oanor.com/antenna-api

Electromagnetic-wave maths as an API, computed locally and deterministically. The convert endpoint converts between wavelength and frequency (λ = c ÷ f) and also reports the period, the wavenumber, the photon energy and the part of the spectrum — optionally for light travelling in a medium of a given refractive index, where the wavelength scales by 1/n while the frequency stays the same. The energy endpoint gives the photon energy in joules, electron-volts and kilo-electron-volts from a wavelength or frequency (E = h·f = h·c ÷ λ). The band endpoint classifies a wavelength or frequency into the electromagnetic spectrum — radio, microwave, infrared, visible, ultraviolet, X-ray or gamma — and adds the ITU radio sub-band (ELF through EHF) and the approximate colour for visible light. Frequencies accept Hz/kHz/MHz/GHz/THz and wavelengths m/cm/mm/µm/nm/pm/ångström. Everything is computed locally and deterministically, so it is instant and private. Ideal for RF and antenna tools, optics and photonics, spectroscopy and lab software, physics and astronomy education, and amateur radio. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is electromagnetic-wave physics; for general unit conversion use a unit-conversion API.

api.oanor.com/wavelength-api

Measure the information content of text. The analyze endpoint computes the Shannon entropy in bits per symbol, the total information in bits and bytes, the maximum possible entropy for the alphabet that was actually used, and a normalized 0–1 score that says how uniform (random-looking) the distribution is — over Unicode code points or raw UTF-8 bytes. The frequency endpoint returns the full character-frequency distribution, most common symbol first, with counts and percentages, showing control characters escaped and bytes as hex. It is exact, deterministic and runs entirely locally with no network calls, so it is instant and private. Ideal for randomness and password-quality checks, estimating how compressible data is, language and classical-cipher analysis, spotting low-variety or repetitive input, and feature extraction for text classification. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This measures information content; for password-strength scoring use a password API, for number statistics use a statistics API, and for grapheme/character counts use a text-segmentation API.

api.oanor.com/entropy-api