12m-15m-17m fan dipole.

[ai8o]

I am thinking about making a 12-15-17m fan dipole.
Similar to the Alpha delta DX-cc.

I have a straight line 67 foot space to mount this antenna, supported at either end by trees,
heighth wolud be 20+ at one end, and about 35 feet at the other.

It would cross over my DXCC antenna about 7 to ten feet above it at about a 75 degree angle.
Of course it will have to be slightly shorter to allow for insulators on either end.
So maybe I have 64 feet to work in.

The antenna would be three separate half wave dipoles (12-15-17m), connected to a center insulator that accepts a PL-259.
This is so I can feed the antenna with rg-8x or rg-8.

I dont't want to use an antenna tuner.

Does anyone have any suggestions on what center insulator or balun to use here?

AI8O

 

[W5lz]

Personally, I don't think there's a real good reason to use a balun with this type antenna. If you like how connections are made on a balun, why not just make a center insulator like that? There are a bunch of them around. Got some plexiglass or simular stuff? Just takes drilling a few holes and adding a connector...

 

[prcguy]

I would use a good ferrite 1:1 choke balun to keep RF off the feedline. The wire lengths will probably come out somewhat shorter than a single band dipole due to interaction and extra capacitance from the unused elements. Tuning may also be a little tricky until you get all the lengths close.

There will also be some interaction with the other antenna nearby and lots of coupling. I have a 133ft offset center fed dipole with the balun near the top of my tower. I also have a 10-20-40m trapped 1/4 wave sloping down from the top of the tower at 90deg to the OCFD. When I run 1.2kW on the offset center fed I can measure about 10 watts of power at the end of the coax for the sloper. That will damage most radios.

 

[W5lz]

What exactly is a 1:1 choke balun? A choke or a balun? Big difference...