This keeps coming up from time to time... Early 80's
IIRC in QST. 105 ohms, losses started getting
appreciable above 10MHz. I think DeMaw (or one of the
other "big names") did the article.
Shawn KB1CKT
--- "Dr. Gerald N. Johnson"
<geraldj@storm.weather.net> wrote:
> On Sat, 2007-01-27 at 07:39 -0600, GARY HUBER wrote:
> > Common "lamp cord" (parallel conductors), has been
> used as twin lead and has
> > an impedance of "about" 72 Ohms depending on the
> exact conductor diameter /
> > spacing / dielectric rating of the insulation.
> >
> > Best regards,
> > Gary - AB9M
> > CSM(r) G.L.Huber
> > 9679 Heron Bay Road
> > Bloomington, Illinois 61704
> > (309)662-0604
>
> Generally the dielectric material in lamp cord is
> significantly more
> lossy at RF than real transmission lines. In the
> early days of ham use
> of transmission lines I've read that twisted rubber
> and cloth insulated
> line cord was used for some feed lines, but it was
> noticeably lossy at
> 80 meters. The modern plastics are better but not
> really great yet.
> There was an article in QST about using zip cord a
> couple years ago.
>
> 73, Jerry, K0CQ
>
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>
Shawn Upton, KB1CKT
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