Per Ralph Mowery:
How tall (far off the ground ) is this antenna ?

Also how far above the roof of the bulding is it ?

14', which puts it 3' above the roof of the garden shed.

I am pretty sure that will work, because my breadboard implementation
has the antenna attached to an 11' pruning pole with the antenna just an
inch or so off the roof.
--
Pete Cresswell