Calculators

Antennas
Dipole calculator From the Larkfield Amateur Radio Club.

Dipole and inverted V calculator from the Carolina DX association

J-Pole calculator From K4ABT

Ground Plane antenna (Quarter wave) Frome Computer Support Group

Loop antenna Dimension calculator from KA1FSB.

Cubical Quad From N6ACH

Vertical Antenna From Computer Support Group

Yagi: Three element beam From Computer Support Group

Yagi: Seven element beam From Computer Support Group

Baluns
Half wave 4:1 coax balun From G8AJN.

Narrow band Balun calculator

Circuits and components
Antenna Tuner circuit for a parallel LC antenna tuner from Crystal radio EU.

Parallel resistors Calculate the total resistance of up to 10 parallel resistors. From G8AJN.

Resistors, capacitors, coils, attenuators From SM0VPO.

Feedlines
Coaxial line loss calculator From the Orchard City Amateur Radio Group

Unit Conversions
Metric <-> Other

Most common metric conversions from World Wide Metric

Convert just about any unit you care to name from OnlineConversion.com