Re: [RCSE] calculating height using small angle formula

[Joe & Jan Wurts]

-----Original Message-----
From: Pete S. <[EMAIL PROTECTED]>

>Here's what I came up with. Let's say my two split
>fingers are 1/4" apart 22" from my eyeball. I'll need
>an angular
>measurement for that so the circumference around my
>eye would be 2piR = 138.16". That divided by my 1/4"
>finger
>spread = 552.64. This must be converted to degrees so
>552.64 / 360º = 1.535º.  This is the angular measure
>from my eye to my outstretched fingers.
.....
>I did these over and over and can't find fault. This,
>however, does not mean I'm sure I'm right. I can't
>find any text
>with the formula you give. Can you point me in the
>right direction?

Simple.  The angle that should come from the above
is:
angle = 360º/552.64 = 0.6515 degrees

That is, you had the angle calculation inverted.  (oops!  :-))

Using the equation that you listed, the distance is:
R = 100" / 0.6515 º x 57.3 = 3732" = 733 ft

Alternately, you don't have to solve for the angle at all.

The equation: d = a / 360º x 2piR

Rewrite as: a= d * 360º /(2piR)

Now, the angle is constant, so:
a = d1*360º /(2piR1) = d2*360º /(2piR2)

Solve for R2,

R2 = (d2/d1) * R1

d1 = antenna end diameter
d2 = plane wingspan
R1 = distance to antenna end

This is the same formula that John gave.

Joe


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