[TowerTalk] Fan dipole
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Fri Mar 27 02:20:16 EDT 2015
I currently have a 2-wire "sloping"fan dipole for 75. The ends are held
with a 3' separator made from 1/2" PVC conduit.
End spreader @ 90 to 95 feet
Feed point and common mode choke.
It covers about a third of 75 with both wire being the same length. I
plan on adding a third wire equally spaced so the ends will form a
triangle. The wires will also be of different lengths to get better
A 75 meter, sloping, fan dipole is definitely NOT a balanced antenna.
I'm building a new choke with 7 cores and 1/8th in spacing between the
cores. (Lexan spreaders) I had to add a second choke where the feed
line reaches the tower to keep RF out of the shack. With just the one
choke at the feed point, at about 1 KW out, all the LEDs in the shack
would light. Adding the second choke seemed to tame it as no LEDs light
at full power, and I can detect no RF in the shack.
When I had the antenna facing NE, I heard lots of stations in Europe the
first night it was up. A few nights later I started working them.
I've use the AV640 mounted on a 24' Al mast. On 40 meters I had very
good results. I had equally good results with a half wave, center fed,
sloping dipoles to the NE and NW. an a/B comparison would show one
better and a short time later the other would win. There were several
times at the last sunspot cycle low that 40 was open world wide for 24
hours at a time.
The problem here is a lot 200 X 200 doesn't give a lot of room for
multiple antennas with out interaction. I was amazed at how much the
sloping dipole over 50 feet away affected the AV640 on 40.
On 3/26/2015 3:12 PM, LY2KZ wrote:
> Hello gentlemen,
> I'm considering one antenna for domestic - continental contacts. I'm
> curious about all pros and cons of this construction and possible
> pitfalls. That is a fan dipole having three wires. Something like here
> http://www.hamuniverse.com/multidipole.html One wire is for 7100kHz,
> another for about 3800kHz and third for 3550kHz. My idea is to have
> two bands covered in full. Is there anyone who has had experience with
> fan dipoles? What should I keep in mind before starting to build? Yes,
> tuning perhaps will not be very simple, but hopefully I will manage.
> How far apart wires should be? 10in OK?
> Should all center conductor legs go to the same side or vary left -
> right - left
> This will be low hanging antenna 10-15m. For DX contacts there will be
> another antenna.
> Thank you
> Vytenis LY5T
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> TowerTalk at contesting.com
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