[TowerTalk] sheet metal roof

[K4IA at aol.com]

Can't help with the modeling question but I have a Mosley tribander mounted 
about 18 feet above a metal roof.  On 20 meters, the roof has "some" effect but 
not a lot.  My lowest SWR is a little bit higher than I would have wanted 
maybe 1.5:1.  Mosley warned me the roof might couple with the antenna and pull 
the lowest SWR point lower in frequency.  That didn't happen to me but it looks 
like what you are experiencing.  You didn't say what the lowest SWR was.  Is 
the SWR low enough that you can just shorten the antenna to bring the dip up 
where you want it?

If you are not being heard, I suspect there is something else going on.  Are 
you sure you don't have any issues with the coax, the feed, a balun, or 
feed-line radiation distorting the pattern?

Radio k4ia
Craig "Buck"
Fredericksburg, Virginia USA
FISTS 6702 CC 788 Diamond 64