# Radio & RF Calc

Maidenhead grid squares, path loss, link budgets, Fresnel zones, antenna length, SWR, dBm conversion, Morse and phonetic spelling.

## How to pay

Machine-payable over x402. USDC on: Base (eip155:8453), Solana (solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp), Polygon (eip155:137), Arbitrum One (eip155:42161).
No accounts. No API keys. No signup. The paying wallet is the account.

## Machine-readable

- OpenAPI: https://radio-calc.x402tookit.com/openapi.json
- x402 manifest: https://radio-calc.x402tookit.com/.well-known/x402
- Catalog (free): https://radio-calc.x402tookit.com/catalog
- Health (free): https://radio-calc.x402tookit.com/health
- Uptime (free): https://radio-calc.x402tookit.com/uptime

## Endpoints (9)

### GET /dbm-convert — $0.02
Convert power between dBm, dBW, mW and W, and the RMS and peak voltage across 50 ohms (or your impedance).
Params: value: number, unit: string, ohms?: number
Example: https://radio-calc.x402tookit.com/dbm-convert?value=30&unit=dbm

### GET /dipole-length — $0.02
Wavelength and half-wave dipole, quarter-wave vertical and full-wave loop lengths for a frequency, with velocity factor.
Params: frequencyMHz: number, velocityFactor?: number
Example: https://radio-calc.x402tookit.com/dipole-length?frequencyMHz=14.2

### GET /fresnel-zone — $0.02
Fresnel zone radius for a radio path from distance and frequency, with the 60% clearance needed for a clear link.
Params: distanceKm: number, frequencyGHz: number, zone?: integer, fromTransmitterKm?: number
Example: https://radio-calc.x402tookit.com/fresnel-zone?distanceKm=10&frequencyGHz=2.4

### GET /fspl — $0.02
Free-space path loss in dB from distance and frequency, plus wavelength; or the range that produces a given loss.
Params: frequencyMHz: number, distanceKm?: number, lossDb?: number
Example: https://radio-calc.x402tookit.com/fspl?frequencyMHz=100&distanceKm=1

### GET /link-budget — $0.02
Link budget: received power, fade margin and maximum free-space range from TX power, antenna gains, losses and sensitivity.
Params: txPowerDbm: number, txGainDbi?: number, rxGainDbi?: number, lossesDb?: number, frequencyMHz: number, distanceKm: number, sensitivityDbm?: number
Example: https://radio-calc.x402tookit.com/link-budget?txPowerDbm=14&txGainDbi=2&rxGainDbi=2&lossesDb=2&frequencyMHz=868&distanceKm=5&sensitivityDbm=-120

### GET /maidenhead — $0.02
Convert latitude/longitude to a Maidenhead grid locator (4, 6 or 8 characters) or a locator to its centre and bounds.
Params: latitude?: number, longitude?: number, locator?: string, characters?: integer
Example: https://radio-calc.x402tookit.com/maidenhead?latitude=48.1458&longitude=11.625&characters=6

### GET /morse — $0.02
Encode text to International Morse or decode dots and dashes, with duration at your words-per-minute (PARIS standard).
Params: text: string, action?: string, wpm?: number
Example: https://radio-calc.x402tookit.com/morse?text=SOS&action=encode&wpm=20

### GET /phonetic-spell — $0.02
Spell a callsign, code or name with the ICAO/NATO phonetic alphabet, digits included, flagging unspellable symbols.
Params: text: string
Example: https://radio-calc.x402tookit.com/phonetic-spell?text=W1AW

### GET /swr — $0.02
SWR, reflection coefficient, return loss, mismatch loss and reflected power from SWR, a resistive load, or two power readings.
Params: swr?: number, loadOhms?: number, lineOhms?: number, forwardWatts?: number, reflectedWatts?: number
Example: https://radio-calc.x402tookit.com/swr?swr=2

## Terms

Radio-frequency arithmetic computed locally from the numbers given, using standard textbook formulas, provided as is. Free-space path loss ignores terrain, buildings, weather and antenna patterns, so real links differ. Not engineering certification, and not legal advice about transmitter power, licensing or band use in your country.