[TowerTalk] 80M Yagi - Height Recommendation

[Bill Coleman]

On Jan 4, 2006, at 4:14 PM, Keith Dutson wrote:

> I am planning to install a 2 el 80M Yagi.  Originally it was going  
> on a 120
> foot Rohn 55G tower.  I now have some flexibility and can put it on  
> a taller
> tower, up to 190 feet.  What are the recommended heights for this  
> type of
> beam, and why?  Thanks in advance for your comments.

120 ft / 280 ft = 0.43 wavelength high

190 ft / 280 ft = 0.68 wavelength high

It's generally considered that horizontal antennas don't have much of  
a directional pattern until they are 1/4 wavelength high or higher.  
But, even at 190 feet, you still aren't one wavelength high yet. Not  
even 3/4 wavelength. The ground will have a heavy influence on the  
pattern.

I'd go with higher - you'll have a more distinct pattern from the yagi.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901