Radio and Electronics Cookbook

65

A vertical aerial for 70 cm

Introduction

If the range of your hand-held transceiver is very limited, what you need is a vertical aerial mounted outside. This design is a half-wave dipole fed at the end instead of the middle. Because the impedance of the dipole is high at its ends (and low in the centre), a matching circuit is needed so that this high impedance can be matched to that of the low-impedance coaxial cable. All that is needed is a coil, which increases the electrical length of the aerial to ⅝-wavelength. (Note that the electrical length (i.e. the length as it appears to an RF signal) is not necessarily the same as the actual length.)

Construction

The aerial element and the coil are made from a single piece of 1.5 mm welding ...