Hi Bob
I guess one should ask how big the roof is... Be handy for modeling the
thing.
Since you probably want a set and forget installation with no tuning
needed across the 80m (or other) bands, it may be worthwhile looking to
a resistive terminated antenna rather than trying to make it
resonant/low Z by its size. Kind of like a TFDP but maybe a loop
construction using very thin (say) stainless steel wire. I would guess
that a balun would still be needed but by playing with a terminating
resistor you may be able to make it multiband. Perhaps running around
the edges of the roof above the gutter line wont be very visible.
Does the fire station have one of those hose drying towers? I realize
you want NVIS rather than vertical pol low angle but it may be worth
considering that avenue.
I guess a roof mounted DDRR would be too visible..
A magloop can be small but there might be an efficiency issue there.
A balloon lifted antenna only for use during emergencies or exercises?
If the building is indeed way out in the country are there any trees
within a few 100 yards? Perhaps some underground coax to an antenna
structure would do it. Cecil has this interesting design at
http://www.w5dxp.com/notuner.htm that uses ribbon cable switched in and
out for the bands you want to use. This switching could be remoted with
the use of relays.
Apologies for not being too specific..
Cheers Bob W5/VK2YQA
Bob Dixon wrote:
Our local fire station would like us to provide an HF station to be
operated by hams during an emergencies.