[OKDXA] One more dipole-balun question

[Kim Elmore]

All this does is change the feed impedance (it's always higher) but it's 
also an unbalanced system. You can probably figure it out with an 
antenna modelling program. My recommendation would be a stout choke-type 
1:1 unit that is sometimes called a "current balun." A string of ferrite 
beads on coax would do, but might be expensive if you want to go down 
to, say, 80 m. Or you could buy a 1:1 "current balun" from someplace.

Cheers,

Kim N5OP


On 6/2/2013 11:07 PM, John Geiger (AF5CC) wrote:
> I had previously said that I had a G5RV type dipole that I made myself.  After repairing it today following a run in with a tree branch last Wednesday, I realize that it isn't quite that.  It is more of an "off center fed dipole". It isn't the classic "Windom off center fed" where one leg is twice as long as the onther.  On my antenna one leg is approximately 50 feet long, and the other leg is around 60 to 65 feet.  It is fed with 300 ohm radio shack twin lead-about a 25 foot run, which goes to a 4:1 voltage balun, and then to 75ohm RG-11 coax to the shack.
>
> Given this new revelation, that it is a off center fed dipole, what is now the best balun for the twin lead to coax junction?  I am assuming that it isn't quite a balanced antenna, since the legs aren't equal, so how crucial does a balanced to unbalanced (coax feedline) transformer become?  My main interest is trying to keep the RF off of the coax shield, although I haven't had any real problems with RFI in the shack.
>
> 73 John AF5CC
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