Build or tune your Slim Jim antenna with precision! This calculator provides optimal dimensions like radiator length, stub length, overall length, and feedpoint for your desired VHF/UHF frequency. Get accurate measurements for amateur radio, GMRS, and marine band applications. Perfect for hams and radio enthusiasts seeking efficient, low-angle radiation.
Formula:
λ = c / fLtotal = 0.75 * λ * VFLradiator = 0.25 * λ * VFLstub = 0.25 * λ * VFGap = λ / 100Lfeed = Lstub / 10
Where:
- λ = Wavelength (meters)
- c = Speed of Light (299,792,458 m/s)
- f = Frequency (Hz)
- VF = Velocity Factor (typical wire: 0.95-0.97)
- Ltotal = Total physical length of the antenna
- Lradiator = Length of the radiating element
- Lstub = Length of the matching stub
- Gap = Spacing between parallel elements
- Lfeed = Feedpoint distance from the bottom of the stub for 50 Ohm match