John Popelish wrote:
. . .
Of course, it can't. But a lumped LC network made of perfect, ideal
components can be constructed that mimic the terminal conditions of the
coil in question to any degree of accuracy desired. The caveat is that
you may not explore much of a frequency range if you expect this
idealized model to remain a good mimic. At another frequency, you have
to rebuild it to copy the effects at that frequency. The broader the
frequency range of such a model, the more complexity it must have.

Yes, but you can use an arbitrarily large number of sections, each with
a small amount of L and C, and mimic a transmission line to any desired
degree, over any frequency range you want. And all with zero physical
size in the theoretical case, and arbitrarily small physical size in the
practical case. In the limit of an infinite number of sections of
vanishingly small L and C each, you arrive at the general equations for
a transmission line, valid at all frequencies.

The point I'm trying to make is that you don't need any particular
physical size or any particular length of wire to make something that
behaves like a transmission line to any degree of accuracy.

Roy Lewallen, W7EL

Roy Lewallen wrote:
The point I'm trying to make is that you don't need any particular
physical size or any particular length of wire to make something that
behaves like a transmission line to any degree of accuracy.

and more important to this discussion, you don't need standing waves or
antennas. For any given load impedance, it behaves the same way.

It's a shame Cecil misses that point, and thinks it is standing waves
that affect the system.

73 Tom

Roy Lewallen wrote:
John Popelish wrote:

. . .
Of course, it can't. But a lumped LC network made of perfect, ideal
components can be constructed that mimic the terminal conditions of
the coil in question to any degree of accuracy desired. The caveat is
that you may not explore much of a frequency range if you expect this
idealized model to remain a good mimic. At another frequency, you
have to rebuild it to copy the effects at that frequency. The broader
the frequency range of such a model, the more complexity it must have.


Yes, but you can use an arbitrarily large number of sections, each with
a small amount of L and C, and mimic a transmission line to any desired
degree, over any frequency range you want. And all with zero physical
size in the theoretical case, and arbitrarily small physical size in the
practical case. In the limit of an infinite number of sections of
vanishingly small L and C each, you arrive at the general equations for
a transmission line, valid at all frequencies.

The point I'm trying to make is that you don't need any particular
physical size or any particular length of wire to make something that
behaves like a transmission line to any degree of accuracy.

Oh. Then never mind. :-)

Roy Lewallen wrote:
The point I'm trying to make is that you don't need any particular
physical size or any particular length of wire to make something that
behaves like a transmission line to any degree of accuracy.

Are you admitting that a 75m bugcatcher behaves like
a transmission line?
--
73, Cecil http://www.qsl.net/w5dxp

EVERYTHING has Inductance, Capacitance and Resistance, and therefore
behaves as a transmission line.
----
Reg, G4FGQ

EVERYTHING????

I thought there is/was a restriction that "Everything" must include "a
significant portion of a wavelength".

:-)

Reg Edwards wrote:

EVERYTHING has Inductance, Capacitance and Resistance, and therefore
behaves as a transmission line.
----
Reg, G4FGQ

Dave wrote:
I thought there is/was a restriction that "Everything" must include "a
significant portion of a wavelength". :-)

A lumped-circuit inductance is *NEVER* a significant
portion of a wavelength, by definition and presupposition.
That's the argument being put forth by the lumped-circuit
gurus. :-)
--
73, Cecil http://www.qsl.net/w5dxp

I thought there is/was a restriction that "Everything" must include
"a
significant portion of a wavelength".

===================================

There are no problems. A very short coil behaves as a very short
transmission line.
----
Reg.

Reg Edwards wrote:
I thought there is/was a restriction that "Everything" must include

"a

significant portion of a wavelength".


===================================

There are no problems. A very short coil behaves as a very short
transmission line.
----
Reg.



I'm glad to know that I can substitute a coil of wire every time I
need a transmission line. So tell me, Reg, what
are the specs on the coil I'd need to make a transmission line
transformer to match 75 ohms to 325.33 ohms?
73,
Tom Donaly, KA6RUH

Reg Edwards wrote:

I thought there is/was a restriction that "Everything" must include

"a

significant portion of a wavelength".


===================================

There are no problems. A very short coil behaves as a very short
transmission line.
----
Reg.



C'mon Reg! We both know that a 1/4 inch diameter loop is NOT a
transmission line at 0.1 MHz. :-0