On Fri, 2007-01-26 at 22:41 +0000, Steve Hunt wrote:
> Jerry,
>
> Thanks for the correction. I've never come across the Zo formula involving a
> cosh function and for all these years have been using the log formula in
> "ignorant bliss".
>
> Just shows you're never too old to learn something new :)
>
> 73,
> Steve G3TXQ
>
>
The inverse hyperbolic cosine formula is in some of the better reference
books like the IT&T Radio Engineer's Handbook. Long about, about 1965, I
got tired of not being allowed by the log formula to make low impedance
lines and dug deeper. Then I published and article in "The VHFer" in
1966 showing the difference. Something not in every ham's library I'm
sure.
I thought I might have to resurrect that article and make it into a web
page. Might have to do that someday, though an article posted at:
http://users.triconet.org/wesandlinda/ladder_line.pdf seems to do well.
Cebik's page http://www.cebik.com/trans/par.html starts to do it right
and then messes it up thinking the cosh formula is only good for wide
spacing and goes on to erroneously say the formulas will have conductors
overlapping at low impedance.
It appears there is as much bad data as good data on the internet and if
I did a page I could refer to it, but otherwise I'd just be trying to
shout contrary to the mobs which isn't especially productive.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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