Re: Transmission Line Demonstrators

On Aug 9, 5:08 pm, chris7007 <chris7...@xxxxxxxxx> wrote:
Hi, my name's Chris and currently finishing my college degree in EE. I
was really interested in leaving some sort of legacy for my department
and my professor suggested building a Transmission Line Demonstrator
for her RF and EMC class. I looked up online and could only find 2
sites, one that sold them, and another that gave a very short
description.

Has anyone here ever tried to build one or has any idea what it
entails, as well as any references anyone might have? The help is
greatly appreciated. This isn't for a project by the way, its just one
thing I want to do for my school

The best I've seen, though tedious to make, is a torsion system.
There's a central rod, with connectors at each end, and cross pieces.
The impedance depends on the moment of the cross pieces; the system I
saw used uniform center rods, I believe. (It was a lonnnnggg time
ago, in Bell Labs educational films.) It's especially impressive if
you paint the ends of the cross pieces with fluorescent paint...

I'd say there were perhaps four cross pieces per foot, with central
rods about three or four feet long. The system could be made from
plastic rods or wooden dowels.

The advantage over rope is that you can demonstrate specific
reflection properties, and you can make tapered lines to match
impedances over a range of frequencies. The system in the film had a
motor that could be used for sinusoidal excitation; it just needs to
pull up and down on the end of a cross piece. It must also have had
loads, though I don't remember them specifically.

The images were so vivid to me that I still remember them when
thinking about transmission line problems.

If you decided to do it that way, you could perhaps enlist the help of
some other students and make it a more interesting team effort.

Cheers,
Tom

.

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