A 5/8 wavelength mobile whip
Build a 5/8 wavelength 2m mobile whip from a repurposed CB helical antenna.
Description
A 5/8 wavelength mobile whip antenna for 2 meters can be constructed from a 5-foot CB helical whip, requiring the removal of original wire and installation of a new radiating element made from coax braid. The design incorporates an 8-turn loading coil with 5mm spacing, fabricated from the original whip wire, and utilizes approximately 1400mm of RG-58 coax braid for the radiating element to enhance flexibility and bandwidth.
Final whip length is approximately 1350mm from base to braid end, with tuning adjustments made by trimming the braid. Dual-wall 12mm heat shrink, such as Jaycar WH5643, is recommended for weatherproofing and stabilization, costing around $4.50 per 1200mm length.
Achieving a 1.1:1 VSWR may not be feasible; a 1.5:1 VSWR is considered acceptable. Optimal mobile mounting is centered on the vehicle roof to minimize radiation pattern variations.