> Subject: [TowerTalk] ANTENNA SURFACE AREA VS ROTOR
> Date: Tuesday, June 16, 1998 12:36 PM
> Last question is, would anyone care to guess what the surface area
> would be for a 15M 6 element monobander on a 38 ft boom would be.
> Estimates are OK.
> TNX & 73 Denis, W4DC
I get a different area than the one cited by KJ6Y for the KLM 615 36' 3"
If the boom is 3" dia by 36' the effective area is 6.5 SqFt. If the boom is
2" dia (as in my KLM manual) the area is 4.5 Sq Ft.
The effective area of the 6 KLM elements is 3.6 Sqft.
The reason the antenna area in the KLM data is overstated is due to the
erroneous methods used. KLM is not alone in making this mistake. 6 years
ago the "conventional wisdom" said that one should combine element and boom
areas according to the Pythagoreum theory to obtain a net effective area
(if you payed attention in Trig class it uses the A^2 = B^2 + C^2 formula).
This has since been proven wrong. The maximum effective area of any antenna
is simply the largest of either the elements or the boom.
If your 38' long boom is 2" Dia constant, the effective area is 4.22 SqFt.
If the Dia is 3", the effective area is 6.33 SqFt. This assumes that the
antenna you describe uses small elements, like the KLM that are only 3.6
If your antenna uses big fat elements, then you need to determine if they
have a larger effective area than the boom.
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