Looking at the formula 1005/freq in mhz gives wave length
1005/28.4 is 35.38 feet multiply the .38 to get inches since it is decimal by 1.2 so roughly 35feet 4 1/2 inch or 424 1/2 inches.
element spacing.
Reflector to driven is .15wl,, driven to first director is .125 wl, first director to second director is .15wl
This is the basic beam configuration, there are many and various different configurations of how to design a yagi, for me this formula was the all around best for gain vs rejection as any yagi is a compromise on the element spacing
(moonraker four dimensions on wave length spacing)
reflector to driven is 63.75"
driven to first director is 53"
first director to second director is 63.75"
I rounded off for simplicity sake but that only gives you 15 foot and you do have 16 foot of boom, so if you want to move the reflector back 6 inches to make it 69.75 " from the director and move the second director 6" more to 69.75" this will increase the bandwidth by moving the reflector back from the director and by moving the front director further away it should make your front lobe a little tighter.
some yagi programs have all elements spaced .25wl apart, that will work, but not optimal.
The fun thing about yagi's is experimenting to see which works best for your QTH, the basics are always the same.
As far as element lengths? your driven will be same as a dipole, velocity factor is given consideration.
468/28.4 = 16.47 so round it off to 16'6" divide by two so each element will be 8' 3" from center of boom. This may be a fraction of an inch to long but you are in the ball park for 28.4mhz.
the reflector is 5% larger than the driven.
the first director is 5% smaller than the driven. the second director is 5% smaller than the first director.
In a nutshell that is yagi design by formula use. Now some one can transpose all that information into an antenna modeling program and tell you how it is going to work from their pc monitor screen, I prefer to build it and try it in the real world, on the air.
those dimensions and spacing will get you in the ball park, the rest is for you to have fun with and try different things.
Good luck and hopefully the band will open up and you can try some contacts.
Here is the spacing for the Maco.
from reflector to driven is 63 3/8in then to first director it is 45in and then 86in to last director.
Here is the spacing for the Cushcraft.
from reflector to driven is 52in then to first director is 52in and then 83 1/2 to last director.
they are both 16ft booms and now I dont know which to do, I am trying to figure how to work a free program I found on the net to model these but just can not figure it out.
I might just build it the Cushcraft spacing as it is designed for 10 meter.[/QUOTE]