[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 
frequency coverage.

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.


Roger  (K8RI)

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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Roger (K8RI)

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