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C h a p t e r 2 8 : S u p p o r t s f o r W i r e s a n d V e r t i c a l s 647<br />

Coax to<br />

transmitter<br />

Radials<br />

Insulator<br />

Rope<br />

Insulator<br />

Rope<br />

Insulator<br />

Rope<br />

Insulator<br />

Rope<br />

Figure 28.18A Feeding the mast-Âmounted vertical antenna.<br />

When a vertical is placed atop a mast of any significant height, the support needs to<br />

be more substantial than just a pipe driven into the ground. Not only the vertical but the<br />

mast itself contributes to the total moment arm that exerts a sometimes unexpectedly<br />

large sideward or overturning force on the base.<br />

Figure 28.20 shows a standard chain-Âlink fence post used as a support for either a<br />

vertical antenna or a mast (which could be metal, PVC, or wood). The typical fence post<br />

is 1.25 to 2.00 in OD and made of thick-Âwall galvanized steel. Thus, such a pipe makes<br />

a rugged installation. Some users believe that the pipe will last longer if painted along<br />

Ground level<br />

3 to 4 in. or more<br />

Coax<br />

to XMTR<br />

Buried radials<br />

Figure 28.18B Feeding the ground-Âmounted vertical antenna.

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