[TowerTalk] Fan Dipole

[Ignacy Misztal]

The simplest design by FAR for 2 band dipoles is folded skeleton sleeve
made of ladderline. See links to QST article in
http://www.highonsolder.com/ham-radio/folded-skeleton-sleeve-antennas/

I use one as non-directional antenna for contesting. It is 20/10 design
with an extra wire in the middle of the ladderline for 10m.  Weighs next to
nothing and no mechanical complexity. Now up for 10 years with no
maintenance.

I used to have a commercial 160/80/40 dipole with coils, with a fan dipole
for 30m. Constant maintenance of spreaders. Dismal performance on 160/80m
compared to a 80m doublet fed by ladderline. But it had low SWR at
resonance.

Ignacy, NO9E

On Mon, Feb 17, 2020 at 2:42 PM Jim Brown <jim at audiosystemsgroup.com> wrote:

> On 2/17/2020 11:12 AM, Jeff Widen via TowerTalk wrote:
> > I want to add a 20 meter wire to my 30 meter dipole and am looking for
> suggestions for spreaders to separate the  elements. Half inch PVC pipe
> seems to bulky and heavy, any suggestions for something lighter that will
> hold up to the sun? Also what is the best separation distance?
>
> Hi Jeff,
>
> Over the years, I've made good use of fan dipoles. 1/2-in PVC conduit
> cut into short lengths is what I've always used. I've built fans for 80
> and 40, for 20, 15 and 10, and for 40, 30 and 17. Now that I have good
> Al in the air for 20-6M, my only fan is for 80 and 40. I use a spacing
> of roughly 9-12 inches, with holes drilled into the spacers for wires to
> run through. For the longest element, I use #9 bare copper, with a wire
> jumper soldered around the spacer to hold it in place. The shorter
> element is #12 THHN, and can be held in place at each end by cable
> clamps or split bolts. Spacers are roughly 6 ft apart. That 80/40 fan
> has been up 120 ft or so suspended between redwoods for at least 10
> years. The spacers aren't as pretty as they were when I built it, but
> they haven't broken. They get plenty of UV exposure here in NorCal.
>
> The #9 bare copper was obtained by buying a spool of #8 bare copper from
> the big box store and stretching it by tying one end of a 200 ft length
> to the base of a tree and the other end to the trailer hitch of W6GJB's
> pickup and pulling VERY slowly until it breaks. Glen and I have done
> this several times after I first learned it from WA6NMF about 15 years
> ago. What you end up with is close to hard drawn copper, roughly 20%
> longer than what you started with.
>
> The only trouble I've had with fans is when something broke in a major
> storm, dropping one end, and the fan got tangled in a big madrone.
> Madrones are beautiful trees, but they're death on wire antennas. :)
>
> In a fan, the SWR bandwidth of the shorter element will be reduced by
> about half, while the SWR bandwidth of the longer element is that of a
> single wire dipole.
>
> Two of my fan dipoles are shown on pages 25 and 26 of
> http://k9yc.com/LimitedSpaceAntennasPPT.pdf
>
> 73, Jim K9YC
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