ARSB HF ENGINEERING RESOURCE

Amateur Radio HF Calculator Center

Antenna, Spiderbeam, Yagi, dipole, EFHW, vertical, loop, wavelength, transmission-line, SWR, RF power, propagation and electronic engineering calculators for radio amateurs, experimenters and students.

〰

Frequency & Wavelength

Calculate wavelength plus full, half and quarter-wave lengths.

Frequency (MHz)

↔

Half-Wave Dipole

Calculate practical HF dipole total length and each wire element.

Operating Frequency (MHz)

⌃

Inverted-V Antenna

Calculate each leg and approximate horizontal span from the included angle.

Frequency (MHz)

Apex Included Angle (°)

Wire length is a starting value. Final antenna tuning should be performed at the installed height and location.

━

EFHW Wire Length

Starting length for an end-fed half-wave antenna.

Fundamental Frequency (MHz)

EFHW matching transformers, wire environment, insulation and installation geometry can shift resonance.

📡

¼-Wave HF Vertical

Calculate approximate radiator and radial lengths.

Frequency (MHz)

◯

Full-Wave Loop

Approximate total wire length for an HF full-wave loop.

Frequency (MHz)

□

Square / Delta Loop Dimensions

Convert calculated full-wave perimeter into square or equilateral delta-loop side dimensions.

Frequency (MHz)

〰

Long-Wire Electrical Length

See how many wavelengths a selected wire length represents.

Frequency (MHz)

Wire Length (m)

MHz

HF Amateur Band Finder

Identify the common amateur band associated with an entered frequency.

Frequency (MHz)

🕸

Spiderbeam Dimension Scaler

Scale verified Spiderbeam wire lengths and spacings from one design frequency to another.

Reference Frequency (MHz)

Target Frequency (MHz)

Item Reference m New m

Enter dimensions from your verified Spiderbeam design.

Scale factor = reference frequency ÷ target frequency. Use dimensions from an established Spiderbeam design/manual; this calculator deliberately does not invent proprietary or design-specific dimensions.

⇉

3-Element HF Yagi Starting Dimensions

Approximate reflector, driven element and director lengths for preliminary experimentation.

Center Frequency (MHz)

This is a rough starting-point model, not a final optimized Yagi. Element diameter, boom, spacing, mounting and matching alter the finished design.

Element Length Percentage Adjuster

Increase or decrease antenna element dimensions by a selected percentage.

Existing Length (m)

Adjustment (%)

⇄

Antenna Frequency Scaling

Scale any antenna dimension to a different center frequency.

Original Frequency (MHz)

New Frequency (MHz)

Original Dimension (m)

🔌

Coax Electrical Length

Calculate physical quarter-wave and half-wave coax lengths using velocity factor.

Frequency (MHz)

Velocity Factor

↓

Coax Cable Loss

Calculate total feed-line loss and antenna-end power from manufacturer's loss specification.

Cable Length (m)

Loss (dB / 100 m)

Transmitter Power (W)

Enter the cable manufacturer's attenuation value for your actual frequency.

Quarter-Wave Transformer

Calculate the characteristic impedance needed for a quarter-wave matching section.

Source Impedance (Ω)

Load Impedance (Ω)

Velocity Factor from Measured Length

Estimate velocity factor from a known quarter-wave resonant cable length.

Frequency (MHz)

Measured ¼-wave Length (m)

📶

SWR & Reflected Power

Calculate standing-wave ratio, reflected percentage and return loss.

Forward Power (W)

Reflected Power (W)

1.50 : 1

4% REFLECTED

14 dB RETURN LOSS

GOOD STATUS

⚡

RF Power / Voltage / Current

Calculate RF RMS and peak voltage for a resistive load.

Power (W)

Load Impedance (Ω)

Watts ↔ dBm

Watts

dBm

📡

EIRP Calculator

Calculate effective isotropic radiated power from transmitter power, feed-line loss and antenna gain.

TX Power (W)

Feed-Line Loss (dB)

Antenna Gain (dBi)

🌐

Free-Space Path Loss

Frequency (MHz)

Distance (km)

⇆

Basic RF Link Budget

TX Power (dBm)

TX Antenna Gain (dBi)

Path Loss (dB)

RX Antenna Gain (dBi)

Other System Losses (dB)

LC Resonant Frequency

Inductance (µH)

Capacitance (pF)

Capacitive Reactance

Frequency (MHz)

Capacitance (pF)

Inductive Reactance

Frequency (MHz)

Inductance (µH)

Ohm's Law

Enter any two values.

Voltage (V)

Current (A)

Resistance (Ω)

Power (W)

Enter any two known values.