Asked something similar while ago but this time I will surely build the
thing. So, I will put up a vertical over metal roof. Roof is 11 by 35
metres, 17m from ground, vertical will be 7m from one end of the roof,
support (a fishing pole) will be 9.5m high. Feeder will be unbalanced
open wire (173 ohms) described by K7JEB in this group.
And then autotuner. I want to operate on 30 and 17, 40 would be bonus,
20 optional. 80 would be very nice too......
Shortly, would like to have a compromise antenna for 80, 30, 17.
Autotuner will do the work but why not try to make it bit easyer fot
it. To get 80, i feel that i need to coil the wire around the fishing
pole. If I would coil 20 metres, would feedpoint impedance be same
(yes, not efficiency) as if wire would be stretched out? If not, should
I coil more or less and by what margin? And what length for feedline?
Minimum would be 8m. I guess I'd like to have some kind of "vertical
G5RV". Did some modeling using 4nec2 but its like banging head against
wall.. So, any educated guess/opinnion/suggestion will be most welcome.
Otherwise I will cut everything random and, I'm afraid, result will be
appropriate too..
Sorry for lenghty post.


Andrus