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On Wed, 12 Dec 2007 21:52:48 -0800, Roger wrote:

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Hi Roger,

99.9999% of posters here use unformatted text which makes responses
very readable.

73's
Richard Clark, KB7QHC

Loading Coils; was : Vincent antenna
 

On Dec 13, 12:52 am, Roger wrote:
Keith Dysart wrote:
clip text...........After considerable thought, I think the math you presented above is for one of two cases of reflective waves, the reflection from a higher impedance load. When the load is less than the Zo of the line, the currents add but voltages subtract. Right?I don't think so. Vt = Vf + Vr, It = If - Ir, Vf = If * Z0 and Vr = Ir * Z0 are the fundamental equations defining forward and reverse waves. Perhaps you arrive at two choices because sometimes Vr and Ir are negative, which after simplification appears to give an alternate form?The end result is the same for both cases.This is good. If you chase the signs, though, I think you will find that there is only one case. We probably should not toss Power into the mix until agreement is reached on this. Power is fraught with issues which seriously confuse some. ...KeithI can see that I need to further explain.
My analysis always begins with the source because the first formation of the wave comes from the source, then travels through the transmission line system. The source defines the waveonlyuntil the wave reaches any discontinuity(s) or the line end. Thereafter, discontinuities and end conditions define the system,.
Why might I say that? Initiation of the wave at the source results in a sine wave with the impedance of the transmission line, and the power and frequency of the source. This is a steady state condition until the first discontinuity or reflection point is reached by the traveling wave. Each successive reflection point (discontinuity) reflects power which travels back to the source and changes the feed point impedance conditions. The most distant possible reflection point is the end of the transmission line (ignoring reflections which might occur on the antenna) and might be an open circuit, a reactive resistance, or a short circuit. Any power reflected from the end will change themeasuredimpedance found atany pointon the transmission line all the way back to the source, and will define the steady state conditions of the system.
If we accept that the steady state conditions are defined by the load, then we should examine the conditions on the source side of the load, assuming it is the end of the transmission line. The forward wavespawnsthe reflective wave in one of two ways, one way of load resistance higher than line impedance, and a second way of load resistance lower than line impedance. In both cases the power of both forward and reflective wave add, but the voltages and currents both add and subtract. (Cecil explained it very well in his follow up postings. Thanks Cecil.) I presented the power equations to illustrate the two conditions.
It is convenient that both cases result in the same math for the directional watt meter.

I'd still suggest that you have the cart and the horse backwards.

The math came first and that is why all the example cases turn out
to be consistent with the math.

And just for completeness...
The fundamental equations also work when:
- the signal is not sinusoidal, e.g. pulse, step, square, ...
- rather than a load at one end, there is a source at each end
- the sources at each end produce different arbitrary functions
- the arbitrary functions at each end are DC sources
It is highly instructive to compute the forward and reverse
voltage and current (and then power) for a line with the same
DC voltage applied to each end.

....Keith

....Keith

Loading Coils; was : Vincent antenna
 

Richard Clark wrote:
On Wed, 12 Dec 2007 21:52:48 -0800, Roger wrote:


!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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head
meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"
title/title
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Hi Roger,

99.9999% of posters here use unformatted text which makes responses
very readable.

73's
Richard Clark, KB7QHC


Thanks Richard, I will use text from now on. Sorry for the inconvenience.

Roger

Loading Coils; was : Vincent antenna
 

Roger wrote:

...
Thanks Richard, I will use text from now on. Sorry for the
inconvenience.

Roger

HTML is not a problem for many of us, any decade old/decent newsreader
handles it fine--if you have .html enabled ...

Regards,
JS

Loading Coils; was : Vincent antenna
 

Keith Dysart wrote:
On Dec 13, 12:52 am, Roger wrote:

Keith Dysart wrote:


Clipping text.............
I'd still suggest that you have the cart and the horse backwards.

The math came first and that is why all the example cases turn out
to be consistent with the math.

And just for completeness...
The fundamental equations also work when:
- the signal is not sinusoidal, e.g. pulse, step, square, ...
- rather than a load at one end, there is a source at each end
- the sources at each end produce different arbitrary functions
- the arbitrary functions at each end are DC sources
It is highly instructive to compute the forward and reverse
voltage and current (and then power) for a line with the same
DC voltage applied to each end.

...Keith

...Keith

Interesting! The important thing is to get answers that agree with
our experiments.

I have done some computations for DC voltage applied to transmission
lines. The real surprise for me came when I realized that transmission
line impedance could be expressed as a function of capacitance and the
wave velocity. Z0 = 1/cC where c is the velocity of the wave and C is
the capacitance of the transmission line per unit length.

73, Roger , W7WKB

Loading Coils; was : Vincent antenna
 

Roger wrote:
Thanks Richard, I will use text from now on. Sorry for the
inconvenience.

I didn't even notice with Thunderbird since I had the
display HTML as plain text option selected.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:

...
I didn't even notice with Thunderbird since I had the
display HTML as plain text option selected.

That's because you have good taste and Thunderbird ROCKS! (the
newsreader, NOT the wine ;-) )

Regards,
JS

Loading Coils; was : Vincent antenna
 

On Thu, 13 Dec 2007 08:40:53 -0800, Roger wrote:

And just for completeness...
The fundamental equations also work when:
- the signal is not sinusoidal, e.g. pulse, step, square, ...
- rather than a load at one end, there is a source at each end
- the sources at each end produce different arbitrary functions
- the arbitrary functions at each end are DC sources
It is highly instructive to compute the forward and reverse
voltage and current (and then power) for a line with the same
DC voltage applied to each end.

...Keith

...Keith

Interesting! The important thing is to get answers that agree with
our experiments.

I have done some computations for DC voltage applied to transmission
lines. The real surprise for me came when I realized that transmission
line impedance could be expressed as a function of capacitance and the
wave velocity. Z0 = 1/cC where c is the velocity of the wave and C is
the capacitance of the transmission line per unit length.

Hi Roger,

This last round has piqued my interest when we dipped into DC. Those
"formulas" would lead us to a DC wave velocity?

73's
Richard Clark, KB7QHC

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
Keith Dysart wrote:

Can you expand on the two different interpretations of
"transfer" that will bring these views into alignment?

Perhaps you really are disagreeing on whether EM
waves always transfer energy (using the common
definition of "transfer").


Jim refuses to provide a reference for his definition
of "transfer".

As I have said before, I am using whatever definition is used, for
example, by Haliday and Resnick when they talk about power. I am not
able to inquire as to what exact definition they use. All I know is
when you say that energy is "transferring" in a transmission line, and
then try to use that statement as proof that "power is moving" in a
transmission line, you have the wrong idea about transfer of energy.
That is precisely where this discussion originated, but I'm sure that
you will disagree - as it is your nature to be highly disagreeable on
this subject.

ac6xg

Loading Coils; was : Vincent antenna
 

Jim Kelley wrote:
aAll I know is
when you say that energy is "transferring" in a transmission line, and
then try to use that statement as proof that "power is moving" in a
transmission line, you have the wrong idea about transfer of energy.

I recently tried, on this newsgroup, to explain to Richard
Harrison that power does *NOT* move in a transmission line.
Richard thinks that power does move as do most of my
engineering textbooks and the IEEE. Johnson, Ramo, and Whinnery
all talk about "power flow". Because it was hairlipping you,
I removed any reference to "power flow" from my magazine
article in support of your concept that power does not flow.

I have *NEVER* said "power is moving", at least not in this
century. That is just your straw man raising its ugly head
yet once again. Jim, when you force yourself to bear false
witness about what I have said, you are essentially giving
up whatever integrity and ethics you ever had. Why you have to
resort to such underhanded unfair techniques speaks volumes.
--
73, Cecil http://www.w5dxp.com