I am following some conversations elsewhere discussing materials to
build transmitting loop antennas from. There are the usual tradeoffs
between aluminum and copper. But some are suggesting that strap can be
used in place of tubing.

My understanding of the skin effect does not cover the required math to
describe the current gradient on the rectangular cross section of a
strap. I found a couple of papers on this, but they tend to analyze
things mathematically without ever actually giving detail of the current
gradient in two dimensions.

Most importantly I'm curious if the strap shape results in the current
being concentrated to the edges of the strap rather than being spread
across the long sides. One reference did refer to the current being
concentrated in the corners and so analyzed what they called a "stadium"
cross section which was just the rectangular strap with half circles for
the short edges rather than straight edges. That author gave numbers
showing the ratio of tube diameter with an equivalent conductivity to
the strap of equal thickness. The "stadium" strap was about 10% better
than the strap with corners. In all cases it was assumed that the strap
was many skin depths in thickness.

I guess I would like to see some sort of graph or shaded diagram to
indicate the current density across such a strap, perhaps one not so
much thicker than the skin depth.

Anyone here use a strap loop antenna and can tell how they compare to a
tubing loop antenna?

--

Rick

On Fri, 23 Oct 2015 03:18:22 -0400, rickman wrote:

I am following some conversations elsewhere discussing materials to
build transmitting loop antennas from. There are the usual tradeoffs
between aluminum and copper. But some are suggesting that strap can be
used in place of tubing.

My understanding of the skin effect does not cover the required math to
describe the current gradient on the rectangular cross section of a
strap. I found a couple of papers on this, but they tend to analyze
things mathematically without ever actually giving detail of the current
gradient in two dimensions.

Most importantly I'm curious if the strap shape results in the current
being concentrated to the edges of the strap rather than being spread
across the long sides. One reference did refer to the current being
concentrated in the corners and so analyzed what they called a "stadium"
cross section which was just the rectangular strap with half circles for
the short edges rather than straight edges. That author gave numbers
showing the ratio of tube diameter with an equivalent conductivity to
the strap of equal thickness. The "stadium" strap was about 10% better
than the strap with corners. In all cases it was assumed that the strap
was many skin depths in thickness.

I guess I would like to see some sort of graph or shaded diagram to
indicate the current density across such a strap, perhaps one not so
much thicker than the skin depth.

Anyone here use a strap loop antenna and can tell how they compare to a
tubing loop antenna?


You are a millionaire?

https://www.cst.com/Products/AntennaMagus

They used to have nice screenshots on display,
but cannot find any now.
Salesmen taking over the company?
****'em.

w.

On 10/23/2015 3:34 AM, Helmut Wabnig wrote:
On Fri, 23 Oct 2015 03:18:22 -0400, rickman wrote:

I am following some conversations elsewhere discussing materials to
build transmitting loop antennas from. There are the usual tradeoffs
between aluminum and copper. But some are suggesting that strap can be
used in place of tubing.

My understanding of the skin effect does not cover the required math to
describe the current gradient on the rectangular cross section of a
strap. I found a couple of papers on this, but they tend to analyze
things mathematically without ever actually giving detail of the current
gradient in two dimensions.

Most importantly I'm curious if the strap shape results in the current
being concentrated to the edges of the strap rather than being spread
across the long sides. One reference did refer to the current being
concentrated in the corners and so analyzed what they called a "stadium"
cross section which was just the rectangular strap with half circles for
the short edges rather than straight edges. That author gave numbers
showing the ratio of tube diameter with an equivalent conductivity to
the strap of equal thickness. The "stadium" strap was about 10% better
than the strap with corners. In all cases it was assumed that the strap
was many skin depths in thickness.

I guess I would like to see some sort of graph or shaded diagram to
indicate the current density across such a strap, perhaps one not so
much thicker than the skin depth.

Anyone here use a strap loop antenna and can tell how they compare to a
tubing loop antenna?


You are a millionaire?

Yes, as a matter of fact I am. Why do you ask?


https://www.cst.com/Products/AntennaMagus

They used to have nice screenshots on display,
but cannot find any now.
Salesmen taking over the company?
****'em.



--

Rick