Double Extended Zepp Antenna

For best results, antenna should be tuned to operating frequency by means of grid-dip oscillator.

Col ¡near The simple colinear antenna array Arrays is a very effective radiating system for the 3.5-Mc. and 7.0-Mc. bands, but its use is not recommended on higher frequencies since such arrays do not possess any vertical directivity. The elevation radiation pattern for such an array is essentially the same as for a half-wave dipole. This consideration applies whether the elements are of normal length or are extended.

The colinear antenna consists of two or more radiating sections from 0.5 to 0.65 wavelengths long, with the current in phase in each section. The necessary phase reversal between sections is obtained through the use of resonant tuning stubs as illustrated in figure 11. The gain of a colinear array using half-wave elements (in decibels) is approximately equal to the number of elements in the array. The exact figures are as follows:

Number of Elements 2 3 4 5 6 Gain in Decibels 1.8 3.3 4.5 5.3 6.2 As additional in-phase colinear elements are added to a doublet, the radiation resistance goes up much faster than when additional half waves are added out of phase (harmonic operated antenna).

For a colinear array of from 2 to 6 elements,

Collinear Out Phase
Figure 13
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