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API · /antenna-api

Antenna Length API

healthy 3,063 Subscribers

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.

#antenna #dipole #amateur-radio #rf #frequency #developer-tools
api.oanor.com/antenna-api
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Machine-readable spec so AI agents can integrate this API.

/api/antenna-api/openapi.json
/api/antenna-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
91 ms
Server probes · 24h
Subscribers
3,063
active
Total calls
36
last 7 days
status Full status page → · 20 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 11,735 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 11,735 calls/month
  • 2 req/sec
  • Dipole + quarter-wave + element
  • No credit card
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Starter

€13.25 /month

  • 21,350 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 21.35k calls/month
  • 8 req/sec
  • Velocity factor + m/ft/in
  • Email support
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Pro

€33.15 /month

  • 263,500 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 263.5k calls/month
  • 20 req/sec
  • RF / antenna-design pipelines
  • Priority support
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Mega

€71.15 /month

  • 1,360,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 1.36M calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

VSWR & Impedance Match API

VSWR and RF impedance-matching maths as an API, computed locally and deterministically. The vswr endpoint computes the voltage standing-wave ratio and its companion figures — the reflection coefficient Γ = (ZL − Z0)/(ZL + Z0) = √(Pr/Pf), the VSWR = (1+|Γ|)/(1−|Γ|), the return loss −20·log₁₀|Γ| dB, the mismatch loss and the percentage of power reflected and transmitted — from a reflection coefficient, a load and source impedance (Z0 default 50 Ω), or the forward and reflected power. The fromvswr endpoint goes the other way, deriving Γ, return loss and the power split from a VSWR figure. The power endpoint computes the reflected and transmitted power from a forward power and a VSWR or reflection coefficient. Everything is computed locally and deterministically, so it is instant and private. Ideal for RF, antenna, amateur-radio and wireless app developers, antenna-tuning and feedline tools, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is RF impedance match; for antenna gain and aperture use an antenna API.

api.oanor.com/vswr-api

Maidenhead Locator API

Convert between latitude/longitude and the Maidenhead Locator System — the grid-square "QTH locator" (like JN58td or IO91wm) used by amateur radio, APRS and contesting to describe a position compactly. The encode endpoint turns a latitude and longitude into a locator at 4-, 6-, 8- or 10-character precision. The decode endpoint turns a locator back into the centre coordinates, the south-west corner and the size of the grid square. The distance endpoint gives the great-circle distance (kilometres and miles) and bearing between the centres of two locators — the classic "how far and which way is that station". Everything is computed locally and deterministically, so it is instant and private. Ideal for amateur-radio and APRS tools, contest logging, antenna aiming, and grid-based mapping. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the Maidenhead system; for Plus Codes, MGRS, UTM and DMS use a geo-convert API and for precise geodesic distance use a geodesy API.

api.oanor.com/maidenhead-api

Transmission Line API

Transmission-line RF maths as an API, computed locally and deterministically for a lossless line. The input-impedance endpoint transforms a complex load impedance along a line, Zin = Z0·(ZL + jZ0·tanβl)/(Z0 + jZL·tanβl), from the characteristic impedance, the load resistance and reactance and the electrical length in degrees — a quarter-wave (90°) line inverts the load to Z0²/ZL while a half-wave (180°) line repeats it, which is the basis of impedance matching. The quarter-wave endpoint computes the characteristic impedance Z0 = √(Z1·Z2) of a quarter-wave transformer that matches two real impedances, exact at one frequency. The electrical-length endpoint converts a physical line length to its electrical length in wavelengths, degrees and radians at a frequency, using the on-line wavelength λ = vf·c/f with a velocity factor for the dielectric. Impedances are in ohms (the load split into resistance and reactance), electrical length in degrees, physical length in metres and frequency in hertz. Everything is computed locally and deterministically, so it is instant and private. Ideal for RF, antenna-matching, PCB, radar and microwave app developers, stub-matching and transformer-design tools, and electromagnetics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is line impedance transformation; for SWR and return loss use a VSWR API and for microstrip trace geometry a PCB API.

api.oanor.com/transmissionline-api

Waveguide API

Rectangular-waveguide microwave maths as an API, computed locally and deterministically. The cutoff endpoint computes the cutoff frequency fc = (c/2)·√((m/a)²+(n/b)²) and cutoff wavelength of any TEmn or TMmn mode of a rectangular waveguide of inner width a and height b — below the cutoff a mode is evanescent and cannot propagate, and for the usual a > b the dominant mode is TE10 with fc = c/(2a). The guide-wavelength endpoint computes, at an operating frequency, the free-space wavelength, the guide wavelength λg = λ0/√(1−(fc/f)²) which is longer than free space, and the phase velocity (greater than c) and group velocity (the energy speed, below c). The modes endpoint lists every mode that propagates at a given frequency, sorted by cutoff, and identifies the dominant mode — so single-mode operation needs the frequency between the first and second cutoffs. Dimensions are in millimetres and frequencies in gigahertz, with c = 299,792,458 m/s. Everything is computed locally and deterministically, so it is instant and private. Ideal for RF, microwave, radar, satellite and antenna-feed app developers, waveguide-band and component-design tools, and electromagnetics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is metallic rectangular waveguide; for optical-fibre guiding use a fibre API and for SWR a VSWR API.

api.oanor.com/waveguide-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Antenna Length API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Antenna Length API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Antenna Length API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Antenna Length API cost?
Antenna Length API has a free tier with 100 calls / month. Paid plans start at €13.25 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Antenna Length API GDPR-compliant?
All requests to Antenna Length API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/antenna-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/antenna-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/antenna-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/antenna-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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