Re: Can twisted wire replace shielded wire?


Jasen Betts wrote:
> noot sure what you mean:
>
> 1 > air is a dielectric (ie generally non-conductive)
>
> 2 > a solitary bare wire is an antenna, not a transmission line :)
>
>
>
> Bye.
> Jasen
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Ever heard of a G-line? ,AKA " Goubau Line".

See: <http://www.finitesite.com/wetnoodle/We0004.htm>
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"G-string or G-line: No this not something worn by an exotic dancer.
This is a form of rf transmission line. It was developed by Dr. Goubel.
Goubel was in the armed services when he came up with this. A G-line is
a true single wire transmission line system. For all practical
purposes, it is the inverse of a wave guide. With the wave guide the
signal travels through a pipe. With the G-line the signal the signal
travels around the outside of a single wire. Goubel went with the
concept that after a certain point the impedance of rf reaches a
maximum in free space. He devised a system for conversion of the
impedance from a coaxial cable to that of the the impedance of that
around a wire. Much like wave guide, the G-line has upper and lower
frequency limits. The major benefit of a G-line system is its
attenuation over a long run is much lower than other transmission line
system. Losses of 1db per mile at 200 MHz was not unheard of this
system. Is it in use anymore? I don't know. In the mid to late 1950's
it was common place. In the mid 1950's the FCC established the UHF tv
band. UHF stations started spring up all over. Somewhere around the
same time frame the FCC also allowed some VHF stations to be translated
into the UHF band. No tv was equipped with a UHF tuner initially. Many
companies made set top converter units. Nearly all of the early units
were hot carrier diode converters. They worked fine within 15 or 20
miles of a commercial UHF station. Where they fell short was on UHF
translators. Some of the earliest converters had a noise figure well in
excess of 12db, some were as much as 18 or 20db."
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There are many resfferences just do a net search for "g-line" antenna

The damn things really work]
Have lower loss then all but the best ladder line, way less loss
then good 300 Ohm. Of cousre they do leak some RF
whcih may be usefull.

Only for VHF and above.

And inspite of installing several g-line systems, I still don't
believe i them :-)

Terry

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