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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