[Antennaware] Metal roof interaction

[Jon M. Knodel]

Hello,

I am getting ready to install my tower this summer and am looking for some help before I do.  My house has a metal roof that I am afraid is going to interact with the antennas.  

I will be able to completely load the tower with all the antennas that I want to at the 40' height.  This would put the top of the tower only about 25' above the metal roof.  Is this close distance going to affect the antenna performance (3 element SteppIR yagi)?  I can also sacrifice some antenna load and put the tower up to 60'.  This would be the path I would take if the roof would interfere with the antenna at 40'  (trading off antennas for additional height and less interaction with the metal roof).

So, my question is:  how much would the roof interact with my antenna?  Because it is a SteppIR and fully adjustable, is this a concern at all due to the fact that it can be retuned easily?  Or would the radiation pattern be adversely affected?  I appreciate all the help I can get.  Thanks.

Jon, N7XW