Jeff Liebermann wrote:
On Mon, 30 Apr 2012 12:18:29 -0400, John Ferrell
wrote:

I put up a fan inverted -V cut for 80-40-30 a while back just to test.
I use a tuner, as long as the transmitter likes it, I like it.

If it's anywhere near a 1/2 wave dipole, a fan dipole shouldn't need a
tuner. I've built two fan dipoles over the years. Since everything
affects everything else, I spent far too much time adjusting the wire
lengths. I eventually settled on a trapped dipole, which was easier
and worked the first time. Either antenna would work for me except
for the length. I don't have the room for a proper 80 meter dipole.
For the immediate problem, I'll be happy if I can get on 20 meters
(PSK31) and 10 meters (radio club net).


FYI I spent an afternoon with EZNEC exploring fan dipoles.

What I found was the farther apart the wires, the less the interaction,
which is what one would expect from common sense.

From my limited runs it appears that somewhere around 20 degrees is about
where the minimum separation needs to be for practical length adjustments.

At angles less than that be prepared to spend a lot of time pruning.

It doesn't matter if the wires are separated vertically or horizontally
other than horizontal separatation means you need lots of support points.

If the bands are too close together, i.e. 20-17, 17-15, 12-10, you can
never get both bands to "work", i.e. a decent match.

That appears to be also true for trap antennas from some limited EZNEC
modeling.

Of course, there is always the alternative of throwing technology and
money at the problem and just put up whatever wire you can and put an
autotuner up.