Bill Blum wrote in message om...
Hi there--

We've been given permission to mount a few antennas on the roof of one
of the buildings at school, with the only caveat being "don't make holes
in the roof." ...
Hi Bill,
some hams use an old tyre as the base. They lay it flat on the roof. A
lumber or sheet-metal circle fills the center of the tyre. An approx.
0,5 m (2 ft) long tube is attached vertically in its center. (Do not
forget a small hole for rain water dripping.) The tyre is filled with
concrete then. When the concrete hardens, you have a heavy and sturdy
base for a tube mast. Only the rubber tyre is in contact with the
roof, so no damage should be done. You can roll the tyre on the roof
if you have to move it.
If you need a bigger mounting, use a tyre from a truck or several
smaller tyres. The same tyre base adopted for a rope or wire can be
used for attaching guy wires / ropes.

73 Ivan OK1SIP