Putting up a first antenna
Work out the leg lengths, pick the feed point and get the height right.
Start here
Three tasks people come here with most often. Each one has the calculators you need and what is worth reading alongside.
Measuring with a NanoVNA
Turn SWR into numbers you can act on, estimate cable loss and find the fault.
Getting on the air
Find your locator, work out the bearing to the other station and tell when a band is open.
Most used
Calculator sections
Full list →Antenna calculators
24 calculatorsTwenty-four antennas — from the dipole and the magnetic loop to the Moxon, the discone and the parabolic dish — together with matching and the radial system.
Transmission lines and measurement
16 calculatorsCharacteristic impedance and line geometry, cable loss, SWR and return loss, fault location and measuring with a NanoVNA.
Matching and baluns
6 calculatorsHow to join two different impedances without losing anything on the way: L-, Pi- and T-networks, the quarter-wave transformer, the Wilkinson divider and series/parallel equivalents.
Filters and crystals
6 calculatorsLC filters from Butterworth and Chebyshev prototypes, crystal ladder filters, resonator parameters, a diplexer and a notch circuit.
Oscillators and synthesis
4 calculatorsColpitts, Clapp and Hartley LC oscillators, the PLL loop, direct digital synthesis and crystal pulling.
Receive path
4 calculatorsWhat decides how well a station hears: cascade noise figure, sensitivity and the noise floor, linearity and signal levels.
Power and safety
3 calculatorsHow much a station actually radiates and at what distance that is safe: ERP and EIRP, RF exposure distance, and power in decibels.
Propagation and location
11 calculatorsWhere a signal goes and how far: QTH locator, bearing and distance, link budget, urban path loss, MUF, satellites and the grey line.
Coil calculations
27 calculatorsTwenty-seven calculators in four subsections: inductors, ferrite cores, extra calculations, and markings and construction.
Electronics and construction
4 calculatorsWhat no home-built project avoids: PCB trace width, heatsink sizing, basic resistor circuits and the 555 timer.
Measurement and tools
3 calculatorsAccessories for the measurement path — an attenuator and a directional coupler — plus basic wavelength conversion.