I just finished up installing the antenna with about half of the lower (ground
plane) tube above the roof line. Got good field strength all around the antenna
and a SWR of 1.7.
Thanks to all that answered my question.

BTW, last year I had this same antenna mounted to the TV antenna in the
motorhome. Sounded like a slick idea, just crank up the TV antenna and the VHF
antenna was ready to go, or so I thoight. I found several cases of blanking
with this arrangement. I believe the metel TV shaft that I clamped thr VHF
antenna to, was blocking transmittion and reception on that side. My *stand
alone* set-up has fixed this problem.
Peace,
JJ Sinclair