PhosphorCalc

Ten RF calculators every ham needs. Dipole lengths, SWR, coax loss, link budgets, impedance matching, and more. No internet required. Numbers in, numbers out.

RF and antenna calculator for amateur radio operators. Ten standalone calculators on a clean, fast interface. Numbers in, numbers out. No network, no accounts, no subscriptions.

DIPOLE Calculate half-wave dipole, quarter-wave vertical, and full-wave loop antenna lengths for any frequency. Adjustable velocity factor for different wire types. Results in both metres and feet.

WAVELENGTH Bidirectional frequency and wavelength conversion. Enter either value and the other is derived instantly. Identifies standard amateur band allocations (ITU Region 1) automatically.

PATH LOSS Free space path loss calculator with approximate S-meter reading context. Supports kilometres and miles. Result can be imported directly into the Link Budget calculator.

COAX LOSS Feedline attenuation for seven common cable types: RG-58, RG-8X, RG-213, LMR-240, LMR-400, Aircell 7, and Ecoflex 15. Uses log-linear interpolated manufacturer data across frequency. Shows power delivered to antenna from a 100W transmitter. Result can be imported into the ERP calculator.

ERP / EIRP Effective radiated power accounting for transmitter output, feedline loss, and antenna gain. Supports both dBi and dBd gain input. Shows feed power, EIRP, and ERP in watts and dBW.

SWR Standing wave ratio from forward and reflected power readings, or direct SWR entry. Calculates return loss, mismatch loss, reflection coefficient, and power delivered. Colour-coded SWR indicator: green for good, amber for marginal, red for poor.

POWER Ohm's law solver: pick any two of voltage, current, resistance, and power — the other two are calculated. Separate dB conversion section converts between watts, milliwatts, dBm, and dBW.

LINK BUDGET Complete end-to-end signal path analysis. Enter TX power, feedline losses, antenna gains, and path loss to see received signal power in dBm and microvolts, S-meter estimate, and link margin above noise floor. Selectable receiver bandwidth: CW, SSB, FM, or Digital.

LC RESONANCE LC tank circuit calculator. Solve for resonant frequency, inductance, or capacitance given the other two values. Displays inductive and capacitive reactance at resonance as a cross-check.

IMPEDANCE L-network impedance matching calculator. Given source and load impedance at a target frequency, calculates component values for both low-pass and high-pass matching network topologies. Shows Q factor and network orientation.

FEATURES

All calculations update live as you type Tap any result to copy it to the clipboard Cross-tab import: pull coax loss into ERP, path loss into link budget Every calculator includes built-in reference notes explaining the formulae Clear and reset controls on every tab Decimal keypad input throughout No internet connection required — everything runs locally No tracking, no analytics, no data collection

Part of the Phosphor radio suite alongside PhosphorRTTY, PhosphorCW, PhosphorHertz, and PhosphorSol.