[OKDXA] One more dipole-balun question

[John Geiger]

Thanks Kim,

I was looking at a 1:1 current balun when  I believed it was a more balanced 
antenna.  Since it is unbalanced, I didn't know which balun would be best, 
or if it would even be possible to keep the RF off off the coax shield.

73 John AF5CC

----- Original Message ----- 
From: "Kim Elmore" <cw_de_n5op at sbcglobal.net>
To: "Oklahoma - DX news and information" <okdxa at mailman.qth.net>
Sent: Tuesday, June 04, 2013 1:19 AM
Subject: Re: [OKDXA] One more dipole-balun question


> 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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