[TenTec] NEC, ground, grounds, and radials

[Steve Hunt]

Correct!

I believe it was Jerry who pointed me to the accurate formula a couple 
of years ago on this very List. I was considering how to build low 
impedance balanced line with a Zo in the range 50 Ohms to 70 Ohms for a 
Hexbeam application. One look at the published curves told me it 
couldn't be done; but Jerry put me right!

Steve G3TXQ


On 08/01/2011 02:05, Dr. Gerald N. Johnson wrote:
> Like my curves its center to center. The upper trace is using the 276
> log formula and the lower one is the 120 inv hyperbolic cosine function.
> Mine has the spacings on a log scale his is a liner scale. The upper
> trace formula is increasingly inaccurate below 300 ohms impedance with
> 87,000 percent error at a spacing just a hair wider than the conductors
> touching. The wrong formula says you can't get a Z0 less than 87 ohms
> (as published in QST last summer again), but the correct formula gets
> down to practically zero Z0 just before the conductors make contact.
> http://www.geraldj.networkiowa.com/papers/CSVHF2010/lztl1.JPG/
> http://www.geraldj.networkiowa.com/papers/CSVHF2010/lztl2.JPG/
>
> 73, Jerry, K0CQ
>
> On 1/7/2011 7:46 PM, Jack Mandelman wrote:
>> Steve,
>> In your plot how are you defining S, the spacing between conductors?  Is it center to center?  Is it consistent for both the approximated and actual curves?  It appears that only the actual curve uses the center to center definition; in the limit as S-->d  the inner edge to inner edge spacing goes to zero, and Zo also goes to zero.
>>
>> Jack K1VT
>>
>>> Jerry,
>>> A picture paints a thousand words:
>>> http://www.karinya.net/g3txq/temp/ladderline_zo.png
>>> 73,
>>> Steve G3TXQ
>>> On 07/01/2011 22:44, Dr. Gerald N. Johnson wrote:
>>>> /  I've published the same article twice now, once in The VHF'er in 1966/
>>>> /  and last year in the proceedings of the 2010 Central States VHF Conference./
>>>>
>>>> /  So I have it available on line but not in a format that will be found by/
>>>> /  search engines:/
>>>> /  http://www.geraldj.networkiowa.com/papers/CSVHF2010/lztl1.JPG/
>>>> /  http://www.geraldj.networkiowa.com/papers/CSVHF2010/lztl2.JPG/
>>>> /  I suppose I should work up an html page that could be found by a search/
>>>> /  engine and expand it with the history as I have found it./
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