Asimov wrote:

Since a portion of the EM field in open wire line is free to travel
outside the conductor into the environment then we may safely assume
there is an exchange between the environment and the conductor.

If the conductors are perfectly conducting, no part of the field at all
exists within the conductor. With good conductors like copper and at HF
and above, there's very little penetration of the conductor by the
fields, either electric or magnetic. As far as an "exchange" goes, it
sounds like you're trying to describe radiation. If not, what's the
phenomenon you're referring to?

If the
impedance of each is approximately the same then there is less loss in
the interface between the two.

No, that's not true. First of all, a mismatch doesn't cause loss.
Secondly, as I explained in my last posting, the characteristic
impedance of a transmission line isn't the same thing as the
characteristic impedance of free space. If you were to construct a
transmission line with 377 ohms characteristic impedance (numerically
the same as the characteristic impedance of free space), the ratio of
E/H fields between the conductors probably won't be anywhere near 377
ohms, as it is in a plane wave propagating without wires.

It has to do with the reflective
coefficient where the energy is returned.

Well, no. There isn't a bundle of energy trying to escape the line and
bouncing off the air, or bouncing off the air as it travels along the
line, or bouncing off the conductors into the air. So reflection
coefficient isn't applicable here.

You will note 300 ohm open
line has less loss than 100 ohm open line.

Yes, and 600 ohm line has less loss than 377 ohm line. You'll have to
find a way to fit this into your theory if you want to pursue it.

RL The loss in coax is a trade off
to achieve stability.

RL Coax is more stable than open wire line? Does open wire line drift in
RL some way?

It is susceptible to ambient humidity and proximity to conductive
objects (birds, snow, rfi). That is a source of drift in practical
terms.

Thanks for the clarification. Because the differential fields are
completely confined within a coaxial cable, they are indeed more immune
to external influences.

I'm afraid that the conclusions you've reached about loss and
characteristic impedance are based on a poor understanding of
fundamental transmission line operation. The result is some conclusions
that are, and are well known to be, untrue.

If you really feel that you have a viable theory, you should be able to
provide some equations and formulas to quantify the extra loss you're
talking about. The existing theory, formulas and equations, in daily use
for over a hundred years, have been shown countless times to accurately
predict transmission line loss, and they don't include the phenomena
you're describing. So although I think it's highly doubtful that your
formulations will prove more accurate, if you post them they can pretty
easily be tested by actual cable measurement.

Roy Lewallen, W7EL

On Thu, 07 Apr 2005 09:09:51 -0500, Cecil Moore
wrote:

Reg Edwards wrote:
And, believe it or not, all is independent of the length of the line.

How much does an infinitessimally short
line radiate? :-)

Sterba and Feldman in "Transmission Lines for Short-Wave Radio
Systems", Proceedings of the IRE, Volume 20, No 7., July, 1932 give a
formula for the radiated power in a balanced line.

The line length *is* a factor, however, they give a simplified
approximation for the case of a length more than 20 times the line
spacing and the line spacing less than 1/10 lambda.

P/I^2 = 160 * ( pi * D / lambda)^2

whe

P is in watts

I is the RMS current in a matched line

D / lambda is the wire spacing in wavelengths

"Wes Stewart" wrote

The line length *is* a factor, however, they give a simplified
approximation for the case of a length more than 20 times the line
spacing and the line spacing less than 1/10 lambda.

P/I^2 = 160 * ( pi * D / lambda)^2

whe

P is in watts

I is the RMS current in a matched line

D / lambda is the wire spacing in wavelengths

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

I don't see line length in the formula.

What do they say about line lengths less than 20 times wire spacing
for small spacings?
----
Reg.

Wes Stewart wrote:
On Thu, 07 Apr 2005 09:09:51 -0500, Cecil Moore
wrote:

Reg Edwards wrote:
And, believe it or not, all is independent of the length of the
line.

How much does an infinitessimally short
line radiate? :-)

Sterba and Feldman in "Transmission Lines for Short-Wave Radio
Systems", Proceedings of the IRE, Volume 20, No 7., July, 1932 give a
formula for the radiated power in a balanced line.

The line length *is* a factor, however, they give a simplified
approximation for the case of a length more than 20 times the line
spacing and the line spacing less than 1/10 lambda.

P/I^2 = 160 * ( pi * D / lambda)^2

whe

P is in watts

I is the RMS current in a matched line

D / lambda is the wire spacing in wavelengths

Reg Edwards wrote:

Cec, you took the bait.

So just exercise a teeny bit of your imagination.

Suppose you have a generator directly connected to a load resistance
without any line in between.

Let the generator and load terminals both be spaced apart by the same
distance as the conductors of the non-existent line.

The load carries a current along a length equal to the spacing between
its terminals.

The load, by virtue of its length, possesses radiation resistance.

And so radiation occurs with zero line length.

You've told us about radiation from the connections to the generator and
the termination.

Now tell us about radiation from the line.


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

Reg Edwards wrote:

"Cecil Moore" asks -
How much does an infinitessimally short
line radiate? :-)

Cec, you took the bait.

We probably need an adjective to describe line
radiation from a line that isn't there. How
about "phantom radiation"? You know, like
phantom pain from a leg that isn't there? :-)
--
73, Cecil http://www.qsl.net/w5dxp


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On Thu, 7 Apr 2005 23:27:29 +0000 (UTC), "Reg Edwards"
wrote:


"Wes Stewart" wrote

The line length *is* a factor, however, they give a simplified
approximation for the case of a length more than 20 times the line
spacing and the line spacing less than 1/10 lambda.

P/I^2 = 160 * ( pi * D / lambda)^2

whe

P is in watts

I is the RMS current in a matched line

D / lambda is the wire spacing in wavelengths

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

I don't see line length in the formula.


That's because for the condition of length 20 * spacing it drops
out.

What do they say about line lengths less than 20 times wire spacing
for small spacings?

They say a whole bunch of things in a complicated formula full of
cosine integrals, etc. Too complicated to express here in plain
ASCII.

I'll try to scan it to pdf and post is somewhere.

Wes

On Fri, 08 Apr 2005 06:05:49 -0700, Wes Stewart
wrote:


I'll try to scan it to pdf and post is somewhere.

http://www.qsl.net/n7ws/Sterba_Openwire.pdf

Wes Stewart wrote:
http://www.qsl.net/n7ws/Sterba_Openwire.pdf

There seems to be a dotted line for feedline
radiation going to zero as feedline length
goes to zero. :-)
--
73, Cecil http://www.qsl.net/w5dxp


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You've told us about radiation from the connections to the generator
and
the termination.

Now tell us about radiation from the line.

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

Ian, you are falling into the same sort of trap as old wives who
imagine most radiation comes from the middle 1/3rd of a dipole because
that's where most of the current is.

It is self-misleading to consider the various parts of a radiating
system to be separate components which are capable of radiating
independently of each other. They can't. A system's behaviour must
be treated as a whole.

We have already discussed that the power radiated from a generator +
twin-line + load is a constant and is independent of line length.

Total power radiated is equal to that radiated from a wire having a
length equal to line spacing with a radiation resistance appropriate
to that length. The location of the radiator, insofar as the
far-field is concerned, can be considered to be at the load. The
current which flows in the radiator is the same as that flowing in a
matched load. And the load current is independent of line length.

Mathematically, the only way for the total power radiated to remain
constant and independent of line length is for zero radiation from the
line.

In summary, the system as a whole BEHAVES as if there is NO radiation
from the line itself - only from fictitious very short monopoles (or
dipoles?) at its ends.
----
Reg, G4FGQ