Twin-Radial ¼ λ Ground Plane for 70 cm

The driven element of this antenna is a telescopic whip. It is mounted in a tubular aluminium pill box using polythene end-caps as insulators. A BNC flange-type socket is mounted on the bottom end-cap, with its centre pin soldered to the whip.

Twin-Radial ¼ λ 70 cm Ground Plane
Two aluminium-strip radials are bolted on to an aluminium base plate, beneath which the driven element assembly is attached. The whip clears the base plate through a central hole.

Mounting screws ensure that the base plate and the BNC flange make contact with the pill box.

SWR at 435MHz is better than 1.5:1.