Single-conductor transmission line?
 

I recall reading about an impedence matching technique where the conductors
of, say a coax segment, would be spaced slowly more and more apart (like the
braid becoming larger like the shape of a funnel) and extending until only
one conductor (the center conductor) is required for transmission. A similar
setup at the other end of the run would transform the impedence back to
usable levels.
The drawings in the article portrayed the transformation as appearing
like a funnel flaring out slowly with the center conductor eventually the
only conductor - then the same setup at the other end.
The idea of a single-conductor transmission line makes it an inviting
idea, but physically building the impedence matching sections on the ends
look like a real challenge.

Google "G-Line".

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.
"Hal Rosser" wrote in message . ..
I recall reading about an impedence matching technique where the conductors
of, say a coax segment, would be spaced slowly more and more apart (like the
braid becoming larger like the shape of a funnel) and extending until only
one conductor (the center conductor) is required for transmission. A similar
setup at the other end of the run would transform the impedence back to
usable levels.
The drawings in the article portrayed the transformation as appearing
like a funnel flaring out slowly with the center conductor eventually the
only conductor - then the same setup at the other end.
The idea of a single-conductor transmission line makes it an inviting
idea, but physically building the impedence matching sections on the ends
look like a real challenge.

Hal Rosser wrote:
The idea of a single-conductor transmission line makes it an inviting
idea, but physically building the impedence matching sections on the ends
look like a real challenge.

A single-wire transmission line has a Z0 of a few
hundred ohms. A transformer at each end is all you
need for impedance matching. The single-wire section
will radiate but it's surprising to me how much power
can be delivered to a load at the end of the wire.

My Electronics Equations Handbook give the Z0 of a
single-wire transmission line as 138*log(4D/d) where
'D' is the distance above ground and 'd' is the
diameter of the wire. A 0.1" dia. line 30 ft. in
the air has a Z0 of 574 ohms.
--
73, Cecil http://www.qsl.net/w5dxp


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Crazy George wrote:
"Hal Rosser" wrote in message
...
I recall reading about an impedence matching technique where the conductors
of, say a coax segment, would be spaced slowly more and more apart (like the
braid becoming larger like the shape of a funnel) and extending until only
one conductor (the center conductor) is required for transmission. A similar
setup at the other end of the run would transform the impedence back to
usable levels.
The drawings in the article portrayed the transformation as appearing
like a funnel flaring out slowly with the center conductor eventually the
only conductor - then the same setup at the other end.
The idea of a single-conductor transmission line makes it an inviting
idea, but physically building the impedence matching sections on the ends
look like a real challenge.

Google "G-Line".

That's the name. It was once promoted as an alternative to large
waveguide for UHF transmission, until low-loss coax came on the scene.

Unfortunately G-line has a number of practical problems, all involved
with keeping the propagating EM field attached to the single wire, and
preventing it from radiating like a long-wire antenna. If the line
radiates, that energy fails to reach its destination at the other end -
which of course means loss.

I don't understand the detailed EM physics, but G-line does not use the
same TEM mode as coax or parallel line. Basically, Nature never intended
an EM field to propagate along a single wire, so it's always trying to
fall off and radiate. To keep the field attached, the wire needs a
fairly thick, low-loss dielectric covering (bare wire won't work). The
line also needs to be straight and uninterrupted, so practical
installation is extremely critical. G-line is always trying to become a
long-wire antenna. Make any mistakes, and that's exactly what you'll
get.

Coax of course is the complete opposite, so Heliax and other forms of
low-loss hardline have wiped G-line off the map. For many years it has
been nothing more than a technological curiosity.

But now it seems to have made a reappearance as a carrier for BPL. Yet
the same basic problem is still the in any practical installation,
G-line is *always* trying to become a radiating long-wire antenna.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Gobau? After 24 hours, the name came. Maybe another 48 and I can spell it correctly.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.

Close. It's Goubau, from "Surface Waves and Their Applications to
Transmission Lines," J. Appl. Phys., vol. 21, 1950. An interesting
variation is described in "Low-Loss RF Transport Over Long Distances",
by M. Friedman and Richard F. Fernsler, IEEE Trans. on Microwave Theory
and Techniques, Vol. 49, No. 2, Feb. 2001, describing a system the
authors describe as "simple, inexpensive, lightweight, and [having] low
attenuation". They used a strip of aluminum foil 6 cm wide and 0.02 mm
thick with periodic punched holes as the line, strung it around a lab
with the strip suspended by threads, and measured low attenuation. How
this could translate to a practical outdoor system for "long distance RF
transportation" as the authors claim is beyond my feeble imagination.

Roy Lewallen, W7EL

Crazy George wrote:
Gobau? After 24 hours, the name came. Maybe another 48 and I can spell it correctly.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.

On Fri, 08 Apr 2005 21:50:36 -0700, Roy Lewallen
wrote:

Close. It's Goubau, from "Surface Waves and Their Applications to
Transmission Lines," J. Appl. Phys., vol. 21, 1950. An interesting
variation is described in "Low-Loss RF Transport Over Long Distances",
by M. Friedman and Richard F. Fernsler, IEEE Trans. on Microwave Theory
and Techniques, Vol. 49, No. 2, Feb. 2001, describing a system the
authors describe as "simple, inexpensive, lightweight, and [having] low
attenuation". They used a strip of aluminum foil 6 cm wide and 0.02 mm
thick with periodic punched holes as the line, strung it around a lab
with the strip suspended by threads, and measured low attenuation. How
this could translate to a practical outdoor system for "long distance RF
transportation" as the authors claim is beyond my feeble imagination.

Darn it Roy, that's your problem... no imagination. These guys
apparently couldn't see the commercial applications either.

They should have written a companion article in Worldradio News about
the super performance they see when using this stuff to feed E-H and
Fractal antennas.

And if they had been really sharp they would have started a company
ahead of time---let's call it "Foilman"---(apologies to Press Jones)
and been ready to peddle this stuff to hams.

A coupla glowing reviews on eham.com and the money would roll in.

Wes

ps. I going to go out and start punching holes in the elements of my
20-meter beam and see what happens.

Roy Lewallen wrote:
Close. It's Goubau, from "Surface Waves and Their Applications to
Transmission Lines," J. Appl. Phys., vol. 21, 1950. An interesting
variation is described in "Low-Loss RF Transport Over Long Distances",
by M. Friedman and Richard F. Fernsler, IEEE Trans. on Microwave Theory
and Techniques, Vol. 49, No. 2, Feb. 2001, describing a system the
authors describe as "simple, inexpensive, lightweight, and [having] low
attenuation". They used a strip of aluminum foil 6 cm wide and 0.02 mm
thick with periodic punched holes as the line, strung it around a lab
with the strip suspended by threads, and measured low attenuation. How
this could translate to a practical outdoor system for "long distance RF
transportation" as the authors claim is beyond my feeble imagination.

In a Beverage antenna, how much transmit power is lost in the
terminating resistor? We know a Beverage is a very inefficient
transmitting antenna. Could it be because it's a fairly efficient
transmission line? Or is it because of ground losses?
--
73, Cecil http://www.qsl.net/w5dxp

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Roy Lewallen wrote:
Close. It's Goubau, from "Surface Waves and Their Applications to
Transmission Lines," J. Appl. Phys., vol. 21, 1950. An interesting
variation is described in "Low-Loss RF Transport Over Long Distances",
by M. Friedman and Richard F. Fernsler, IEEE Trans. on Microwave Theory
and Techniques, Vol. 49, No. 2, Feb. 2001, describing a system the
authors describe as "simple, inexpensive, lightweight, and [having] low
attenuation". They used a strip of aluminum foil 6 cm wide and 0.02 mm
thick with periodic punched holes as the line, strung it around a lab
with the strip suspended by threads, and measured low attenuation. How
this could translate to a practical outdoor system for "long distance RF
transportation" as the authors claim is beyond my feeble imagination.

Heh, heh, maybe they modeled it with NEC2. Violating the
height above Mininec ground rule yields a source power of
396 watts and a load power of 340 watts (86% efficiency)
for a 1000 foot line, one foot above ground, on 20m. :-)
(While yielding a Beverage antenna gain of 13 dBi)

How would it work between two ships on a calm ocean?

Can the single-wire transmission line be modeled with EZNEC
if the height is greater than 0.2 wavelength?

Can it be modeled with NEC4? If so, could someone do it
and report the results?
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:

In a Beverage antenna, how much transmit power is lost in the
terminating resistor? We know a Beverage is a very inefficient
transmitting antenna. Could it be because it's a fairly efficient
transmission line? Or is it because of ground losses?

Model one with EZNEC to find out. At each end, put a few radial wires
just above the ground to connect the source and terminating resistors
to, and use High Accuracy ground. The Average Gain will tell you the
total loss which includes resistor and ground loss. Click the Load Dat
button to find the loss in the terminating resistor. From those you can
get the amount of ground loss.

Roy Lewallen, W7EL