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
Half wave 4:1 coax balun From G8AJN.
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.
Coaxial line loss calculator From the Orchard City Amateur Radio Group
GPS-enabled mobile phone Maidenhead calculator Works with Nokia N95
Metric <-> Other
Most common metric conversions from World Wide Metric
Convert just about any unit you care to name from OnlineConversion.com