On 16 Nov, 07:06, (Richard Harrison) wrote:
Art wrote:

"I am trying to deduce an alternative to the thinking current can hurdle
a capacitor and retain its time variation."

An early demonstration of electroostatic repulsion was via an instrument
called the electroscope. Put a charge on its plates and it opened like a
book. It proved like charges repelled and that repulsion was
proportional to charge.

From that it can be imagined that if you put a charge on one insulated
plate and like charges on an insulated plate nearby have an avenue of
escape to the outside world, you may have produced a capacitor useful
for ac coupling or bypass. It isn`t a hurdle. It is a device capable of
a displacement current which blocks dc but passes ac. It`s a device
formerly called a condenser, now called a capacitor.

Best regards, Richard Harrison, KB5WZI

I assume you are not trying to be funny and are using the dictates of
Terman to make a point. So I will respond. The antenna am referring to
consists
of a tank circuit where the distributed capacitance is the capacitor
in the circuit.
The capacitor stores energy from the time varying current and then
releases the energy
when the terminals are shorted. This energy is not released with the
same properties
that the capacitor but in a similar way that a battery does when the
terminals are
shorted. Thus the time variant that one sees on the energy release is
not the same
as the time varient possesed when delivered to the capacitor but I
could be in error.
I have most of Termans books so if you can point to a section that
confirms your position
and contradicts mine I would apreciate if you would share that section
with me.
Regards
Art

On 16 Nov, 07:06, (Richard Harrison) wrote:
Art wrote:

"I am trying to deduce an alternative to the thinking current can hurdle
a capacitor and retain its time variation."

An early demonstration of electroostatic repulsion was via an instrument
called the electroscope. Put a charge on its plates and it opened like a
book. It proved like charges repelled and that repulsion was
proportional to charge.

From that it can be imagined that if you put a charge on one insulated
plate and like charges on an insulated plate nearby have an avenue of
escape to the outside world, you may have produced a capacitor useful
for ac coupling or bypass. It isn`t a hurdle. It is a device capable of
a displacement current which blocks dc but passes ac. It`s a device
formerly called a condenser, now called a capacitor.

Best regards, Richard Harrison, KB5WZI

What you must understand is t5he circuit that constitutes a
capacitor part of which is a resister that is seen in parallel.
So yes, a portion of energy can bypass the capacitor.
However the time varient that one must measure is at best,
a superinposed expellation of energy from the capacitor
which changes the original time varient required for radiation.
Cecil makes the point he can measure the current
along the radiator, but in fact he has a measuring problem
by what he is using to measure current with respect to time.
Regards
Art

Art wrote:
"What you nust understand is the circuit that constitutes a capacitor
part of which is a resistor that is seen in parallel."

That would be equivalent to a leaky capacitor.

There is no time delay in a pure resistor. Its voltage drop is in-phase
with the current through it.

I don`t have a complete equivalent circuit in mind.

Best regards, Richard Harrison, KB5WZI

On 17 Nov, 16:57, (Richard Harrison) wrote:
Art wrote:

"What you nust understand is the circuit that constitutes a capacitor
part of which is a resistor that is seen in parallel."

That would be equivalent to a leaky capacitor.

There is no time delay in a pure resistor. Its voltage drop is in-phase
with the current through it.

I don`t have a complete equivalent circuit in mind.

Best regards, Richard Harrison, KB5WZI

Right. The the sino soidal shape will go thru with its time varient
which is the condition applied by programmers for EVERY segment.
But that is only half the story for a TANK circuit. The capacitor
stores energy just like charging a battery, it will not NOT thru.
When the situation is right the capacitor/battery releases all its
energy like
connecting a terminal to ground or shorting it.This allows the energy
to flow in dc format at a rate decides by its time constant ot time
varient
required for radiation. This energy release is imposed on the leakage
current
thus forming a new time varient rquirede for radiation.
Thus at different segment points the time varient is not a reflection
of a sino soidal leakage current but the summation of that PLUS the
capacitor dicharge time constant. Look up a tank circuit and all will
become clear when you follow the phase changes of the voltage and the
current first in forward direction and then the reverse direction.
Regards
Art

Art wrote:
"When the situation is right the capacitor/battery releases all its
energy like connecting a terminal to ground or shorting it."

Not quite. The inductance, whose reactance equals the capacitance`s
reactance at resonance, opposes any change in current. It only allows
current to grow exponentially during the cycle by simultaneously
generating a counter emf to oppose the current imposed on the inductance
from outside. The impressed current will lag the voltage across a pure
inductance by 90 degrees. The voltage builds across a pure capacitance
with a 90 degree lag of the current through the capacitance. This is
basic electricity 101.

Best regards, Richard Harrison, KB5WZI

On 18 Nov, 19:00, (Richard Harrison) wrote:
Art wrote:

"When the situation is right the capacitor/battery releases all its
energy like connecting a terminal to ground or shorting it."

Not quite. The inductance, whose reactance equals the capacitance`s
reactance at resonance, opposes any change in current. It only allows
current to grow exponentially during the cycle by simultaneously
generating a counter emf to oppose the current imposed on the inductance
from outside. The impressed current will lag the voltage across a pure
inductance by 90 degrees. The voltage builds across a pure capacitance
with a 90 degree lag of the current through the capacitance.


This is
basic electricity 101.
Maybe in America!
Since it is resonant then it is a tank circuit where you have to
rethink the
90 degree lag
Art

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Art wrote:
"When the situation is right the capacitor/battery releases all its
energy like connecting a terminal to ground or shorting it."

Not quite. The inductance, whose reactance equals the capacitance`s
reactance at resonance, opposes any change in current. It only allows
current to grow exponentially during the cycle by simultaneously
generating a counter emf to oppose the current imposed on the inductance
from outside. The impressed current will lag the voltage across a pure
inductance by 90 degrees. The voltage builds across a pure capacitance
with a 90 degree lag of the current through the capacitance. This is
basic electricity 101.

A little too basic, I'm afraid. The 90 degree current lag applies only
to a steady state sinusoidal voltage. For other waveforms (like ones
you'd get connecting batteries or capacitors) you have to resort to the
more general time relationship v = L * di/dt. (Or, if inductance is
changing with time, v = d/dt (L * i).)

Roy Lewallen, W7EL

Roy Lewallen wrote:
"S little too basic, I`m afraid. The 90 degree current lag applies only
to a steady state sinusoidal voltage."

A steady state sinusoidal voltage is exactly what I would expect on a
resonant antenna in the absence of modulation when a carrier has been
applied to the antenna for a short but not too short period of time.

Best regards, Richard Harrison, KB5WZI

On 20 Nov, 00:07, "Jimmie D" wrote:
"Richard Harrison" wrote in message

...

Roy Lewallen wrote:
"S little too basic, I`m afraid. The 90 degree current lag applies only
to a steady state sinusoidal voltage."

A steady state sinusoidal voltage is exactly what I would expect on a
resonant antenna in the absence of modulation when a carrier has been
applied to the antenna for a short but not too short period of time.

Best regards, Richard Harrison, KB5WZI

The peril of trying to actualy answer Art's questions.

Richard can be excused for making this error.
This is the same fundamental reason that Ted Hart,
Professor Underhill and lately Vincent failed
to design a radiator that actually works efficiently.
And to this day they and the ham world are totally
oblivious as to why.
This is a direct effect of memorizing facts in college
without regard to first principles to obtain a degree.
Pretty much all examinations I had to take in Europe
demanded a response to a question using only first
principles to avoid failure.
Where failure in any subject during the year required
a repeat of all subjects taken that year, even those
where a pass was obtained, where one has to be successfull,
or thrown out!
Art Unwin KB9MZ....xg (UK)

Art wrote:
"Richard can be excused for making this error."

Prove I erred!

Put a sine wave in an antenna and you get a sine wave out.

Kraus says:
"The currents on the transmission line flow out on the antenna and end
there, but the fields associated with them keep on going."

Art in a previous posting said I should quote "Lady Chatterley`s Lover"
as people were tiring of Terman. I read it before it was even printed in
the U.K. (1960) but this is an antenna newsgroup and Terman is more
appropriate.

If people want something other than Terman, he gives a terrific
bibliography at the bottom of page 864 in his 1955 opus.

Art also said in a previous posting that Terman did not credit Maxwell
with defining radiation. Let me put the lie to that. On page 864 of his
1955 opus, Terman writes:
"The laws governing such radiation are obtained by using Maxwell`s
equations to express the fields associated with the wire; when this is
done there is found to be a component, termed the radiated field having
a strength that varies inversely with the distance."

Best regards, Richard Harrison, KB5WZI