On Apr 23, 7:06*am, Cecil Moore wrote:
Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic. It's open circuited at the end,
so it behaves pretty much like an open circuited transmission line,
resulting in the same reflections and resulting standing waves you see
on a real antenna.

The Z0 characteristic impedance that matters is the
one that exists at the coil-stinger junction which
can be estimated from the single-wire transmission
line Z0 equation. It's usually in the neighborhood
of a few hundred ohms. For instance, a #14 horizontal
wire at 30 feet has a Z0 very close to 600 ohms
according to the formula.

One difficulty is accounting for the radiation, which
adds resistance to the feedpoint. I've never seen an attempt at
simulating it with distributed resistance, which I don't think would
work except over a narrow frequency range.

I have simulated such using EZNEC's wire resistivity
option. The resistance wire simulates the radiation
"loss" from the antenna. But for a standing wave
antenna, the "loss" to radiation is only about 20%
of the total energy stored on the standing wave
antenna. Therefore, a qualitative conceptual analysis
can be done assuming lossless conditions just as it
can be done with transmission lines.

But one
shortcoming of many antenna transmission line analogies is the attempt
to assign a single "average" or "effective" characteristic impedance to
the antenna, rather than the actual varying value. This is where a lot
of care has to be taken to assure that the model is valid in the regime
where it's being used.

Seems EZNEC automatically compensates for the varying Z0
so all we need to estimate is the single effective Z0 at
the coil to stinger impedance discontinuity.

There's no reason you can't also include a loading coil in the
transmission line model, and Boyer devotes much of the second part of
his article to doing just that. A solenoidal coil raises the
characteristic impedance of the length of "line" it occupies, because of
the increase in L/C ratio in that section. The traveling wave delay in
that section of the transmission line also increases due to the
increased LC product.

Are you saying the physics of the delay through a loading
coil changes between a traveling wave and a standing wave???
The standing wave is composed of a forward traveling wave
and a reflected traveling wave. They would experience the
same delay that you are talking about above.

So why didn't you use a traveling wave to measure the delay
through a loading coil??? Exactly how can the following
antenna current (from EZNEC) be used to calculate delay? The
current changes phase by 2.71 degrees in 90 degrees of
antenna. If the antenna was lossless, i.e. no radiation,
that current would not change phase at all.

* * * * * * * * * * * *EZNEC+ ver. 4.0
thin-wire 1/4WL vertical * * 4/23/2009 * * 6:52:13 AM
* * * * * --------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment *Conn * * *Magnitude (A.) *Phase (Deg.)
1 * * * *Ground * * 1 * * * * * * * *0.00
2 * * * * * * * * * .97651 * * * * *-0.42
3 * * * * * * * * * .93005 * * * * *-0.83
4 * * * * * * * * * .86159 * * * * *-1.19
5 * * * * * * * * * .77258 * * * * *-1.50
6 * * * * * * * * * .66485 * * * * *-1.78
7 * * * * * * * * * .54059 * * * * *-2.04
8 * * * * * * * * * .40213 * * * * *-2.28
9 * * * * * * * * * .25161 * * * * *-2.50
10 * * * Open * * * .08883 * * * * *-2.71

--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Cecil
The problem in this debate is that others are concentrating on
resonance
where as you are thinking in terms of anti resonance which portends to
a higher impedance and also the condition of equilibrium. When
considering the boundary law
one must recognise that momentum increases and decreases twice per
period. Thus when considering the boundary laws the negative area of
the sine wave must be placed underneath the positive area such that
momentum is taken account of.
When the diagram provided by Best on this thread was shown what it
described was the period was extended by the containment within the
boundary and where that containment extended the period which is now
longer than the period of non containment.In one case you have
accelleration and deaccelleration which is depicted
as the emmission of energy or flux. Consevation of energy laws demands
that for balance we must take into account the energy or flux that
enters the boundary to maintain equilibrium which is depicted by the
negative area of the sine wave period
such that this area is placed directly under the positive area while
still remaining within the arbritrary boundary. Thus we have
effectively changed the period when looking at a coil where the slow
wave is now half of the original wave as is theresonant point is half
of the anti resonant point which in terms of Newton and Maxwell
represents the point of equilibrium. When using the resonant point in
terms of relativity ie Maxwell you are seeing movement of a charge
from "a" to "b" which when repeated is repetitive movement in a single
direction. When using the anti resonant point the charge returns to
the starting point and if time is regarded as /dt
then the charge only moves in the vertical direction. Thus in terms of
Earth mass consists of energy movement in the ":z" plan and with
respect to the Universe the energy movement is solely in the "x" or
"y": direction until this action is equated with an action from the
opposite direction as per the law of Newton. Thus like Einstein
viewing the same action of Newton this thread is viewing the same
problem where one is static and one is relative but never the less the
same problem but relatively different. Pure physics my dear Watson
viewed fron different vantage points., one takes equilibrium into
account where as the other doesn't.
Not "babble"' David just an explanation per classical physics which is
the sole and only root of both mechanical and electrical engineering
Best regards
Art Unwin KB9MZ xg(uk)