[Towertalk] Yagi Rotational Center

[Mike Gilmer, N2MG]

N4KG wrote:
> Mathematically, calculate the rotational radius to 
> the reflector tip and the director tip from points along
> the boom until they are equal.  

>  (R/2)^2 + Br^2 = Rr  
>  where R = Reflector Length, 
>  Br = distance on boom from reflector to test point

>  (D/2)^2 + Bd^2 = Rd
>  where D = Director Length,
>  Bd = distance on boom from end director to test point

Sharpen that pencil and renew those algebra techniques 
and, FWIW, this reduces to:

Bd = 0.5 * ( ( ( (R/2)^2 - (D/2)^2 ) / Bt ) + Bt ) 

where Bt (total boom length) = Br +Bd

73 Mike N2MG