Distributed capacitance effects Q?
 

"Richard Clark" wrote in message
...
On Sun, 29 Apr 2007 06:52:17 -0500, "amdx" wrote:

I agree with your assertion that distributed winding capacitance
degrades efficiency.
My thoughts about this are ;
Assume a 10 turn loop, between each turn there is a capacitance,
so, you have a complete circuit, (L,C,R) there is current
flowing through this circuit that is not flowing through the entire 10
turn loop. (this happens in the other 9 turns also)
I think these extra currents flowing that don't make the entire 10
turn circuit increase the losses.

Hi Mike,

Capacitance does not bring loss.

I'm not ready to give on that yet, but I could be convinced.
It seems I could add capacitors across turns of a coil and increase
circulating currents that would show as a lower Q. But I haven't
built a coil to test this.

Loss ALWAYS resides in Resistance and nothing else.

I agree, X/R=Q Lower Q means more loss.
(let's not get into radiation resistance right now)


Between you and Bill, there appears to be a fixation on the loopS
(emphasis on there being more than one). If you are going to blame
them (that emphasis on there being more than one), and try to tie it
to loss (that emphasis being naturally in Resistance, not
Capacitance); then it follows it is in the natural increase in
conductor Resistance that occurs when wires are spaced closer than 3
or 4 wire diameters to each other. When wires (or loops in this case)
are in close proximity, the magnetic field of the near wire (or loop
in this case, and each loop in proximity to the next) FORCES the
current in that loop to the surface of the wire - INCREASING that
conductor's Skin Resistance. Loss thus increases by proximity.
Capacitance does too, but that is merely a correlating factor.

Proximity effect could cause all of the additional losses.
Or it might just be part of the additional losses.

Why is it that when you get near self resonance of a coil the Q gets lower?
Note; to help clearify my question,
( as you get nearer and nearer resonance the capacitor you are using to tune
the inductor is getting smaller and smaller, and closer to equalling the
self
capacitance of the inductor)

Remember---Correlation is NOT causality.

If you measure reading skills in an elementary school you will find the
kids with big feet read better.

But then 5th graders usually have bigger feet than kindergarteners.

Thanks for the discussion____

Mike

Distributed capacitance effects Q?
 

"amdx" wrote in message
...

"Richard Clark" wrote in message
...
On Sun, 29 Apr 2007 06:52:17 -0500, "amdx" wrote:

I agree with your assertion that distributed winding capacitance
degrades efficiency.
My thoughts about this are ;
Assume a 10 turn loop, between each turn there is a capacitance,
so, you have a complete circuit, (L,C,R) there is current
flowing through this circuit that is not flowing through the entire 10
turn loop. (this happens in the other 9 turns also)
I think these extra currents flowing that don't make the entire 10
turn circuit increase the losses.

Hi Mike,

Capacitance does not bring loss.

I'm not ready to give on that yet, but I could be convinced.
It seems I could add capacitors across turns of a coil and increase
circulating currents that would show as a lower Q. But I haven't
built a coil to test this.

Loss ALWAYS resides in Resistance and nothing else.

I agree, X/R=Q Lower Q means more loss.
(let's not get into radiation resistance right now)


Between you and Bill, there appears to be a fixation on the loopS
(emphasis on there being more than one). If you are going to blame
them (that emphasis on there being more than one), and try to tie it
to loss (that emphasis being naturally in Resistance, not
Capacitance); then it follows it is in the natural increase in
conductor Resistance that occurs when wires are spaced closer than 3
or 4 wire diameters to each other. When wires (or loops in this case)
are in close proximity, the magnetic field of the near wire (or loop
in this case, and each loop in proximity to the next) FORCES the
current in that loop to the surface of the wire - INCREASING that
conductor's Skin Resistance. Loss thus increases by proximity.
Capacitance does too, but that is merely a correlating factor.

Proximity effect could cause all of the additional losses.
Or it might just be part of the additional losses.

Why is it that when you get near self resonance of a coil the Q gets
lower?
Note; to help clearify my question,
( as you get nearer and nearer resonance the capacitor you are using to
tune
the inductor is getting smaller and smaller, and closer to equalling the
self
capacitance of the inductor)

Remember---Correlation is NOT causality.

If you measure reading skills in an elementary school you will find the
kids with big feet read better.

But then 5th graders usually have bigger feet than kindergarteners.

Thanks for the discussion____

Mike


Hi Mike

I am curious about how the comment in your post ---
It seems I could add capacitors across turns of a coil and increase
circulating currents that would show as a lower Q. But I haven't
built a coil to test this.
I would have thought that, when the circulating current increases when a
passive devce is introduced, the Q would have Increased.

Jerry

Distributed capacitance effects Q?
 

On Sun, 29 Apr 2007 14:30:29 -0500, "amdx" wrote:

Capacitance does not bring loss.

I'm not ready to give on that yet, but I could be convinced.
It seems I could add capacitors across turns of a coil and increase
circulating currents that would show as a lower Q. But I haven't
built a coil to test this.

Hi Mike,

This is then a characteristic of the Capacitor called D (dissipation).
Any increase in current tied to loss immediately goes to the bottom
line of resistance - it is a square law relationship, after all.

Loss ALWAYS resides in Resistance and nothing else.

I agree, X/R=Q Lower Q means more loss.
(let's not get into radiation resistance right now)

Why not? Small loops suffer by comparison, and multi-turn loops even
more so.

Proximity effect could cause all of the additional losses.
Or it might just be part of the additional losses.

For wire separations beyond 3 or 4 wire diameters, the increase in
skin effect is small. It might be noted that interwinding Capacitance
also falls.

Why is it that when you get near self resonance of a coil the Q gets lower?
Note; to help clearify my question,
( as you get nearer and nearer resonance the capacitor you are using to tune
the inductor is getting smaller and smaller, and closer to equalling the
self
capacitance of the inductor)

Again, the answer must reside in Resistance. There are many
characteristics (wavelength, solenoid diameter, length, pitch, wire
gauge, self-capacitance, distributed capacitance, balance,
connections, earth proximity, radiation resistance) being juggled with
small Loop antennas and some (even many) choices that can be made to
resonate the antenna do not lead to an efficient solution.

73's
Richard Clark, KB7QHC

Distributed capacitance effects Q?
 

"Richard Clark" wrote in message
...
On Sun, 29 Apr 2007 14:30:29 -0500, "amdx" wrote:

Capacitance does not bring loss.

I'm not ready to give on that yet, but I could be convinced.
It seems I could add capacitors across turns of a coil and increase
circulating currents that would show as a lower Q. But I haven't
built a coil to test this.

Hi Mike,

This is then a characteristic of the Capacitor called D (dissipation).
Any increase in current tied to loss immediately goes to the bottom
line of resistance - it is a square law relationship, after all.

So your saying yes, the thought experiment would show more loss,
but the loss is in the capacitor. The loss in a capacitor would be
dielectric
and loss in the plates right?


Loss ALWAYS resides in Resistance and nothing else.

I agree, X/R=Q Lower Q means more loss.
(let's not get into radiation resistance right now)

Why not? Small loops suffer by comparison, and multi-turn loops even
more so.

I figure it would only confuse the issue.
I was trying to stay away from radiation resistance because my experience of
the effect Bill ask about has been with small aircore inductors. But on
second thought
even those have Rr.

Proximity effect could cause all of the additional losses.
Or it might just be part of the additional losses.

For wire separations beyond 3 or 4 wire diameters, the increase in
skin effect is small. It might be noted that interwinding Capacitance
also falls.

Why is it that when you get near self resonance of a coil the Q gets
lower?
Note; to help clearify my question,
( as you get nearer and nearer resonance the capacitor you are using to
tune
the inductor is getting smaller and smaller, and closer to equalling the
self
capacitance of the inductor)



Again, the answer must reside in Resistance. There are many
characteristics (wavelength, solenoid diameter, length, pitch, wire
gauge, self-capacitance, distributed capacitance, balance,
connections, earth proximity, radiation resistance) being juggled with
small Loop antennas and some (even many) choices that can be made to
resonate the antenna do not lead to an efficient solution.

Richard, I don't think anyone would disagree that the losses are resistive.
You seem to have answered the question I posted by saying it's increased
resistance.
Yes I agree,
Why does the reistance go up near resonance?

Mike

Distributed capacitance effects Q?
 

On Sun, 29 Apr 2007 15:36:43 -0500, "amdx" wrote:

This is then a characteristic of the Capacitor called D (dissipation).
Any increase in current tied to loss immediately goes to the bottom
line of resistance - it is a square law relationship, after all.

So your saying yes, the thought experiment would show more loss,
but the loss is in the capacitor. The loss in a capacitor would be
dielectric
and loss in the plates right?

Hi Mike,

Depending upon construction, most assuredly. However, little loss is
found in dielectrics (unless you are using particularly crummy
examples). For bad dielectric, you can expects arcs and sparks
followed by carbon, and then catastrophic heat accumulation. Most
lost is in what is specified in ESR (effective series resistance)
which you have already identified as in the plates, but often more in
the leads and their connections to the plates. To pack in more
capacitance, the trend is for thinner plates for a given package
volume. You can guess where the resistance will rise there when the
circulating currents are see-sawing in that thin metal.

(let's not get into radiation resistance right now)

Why not? Small loops suffer by comparison, and multi-turn loops even
more so.

I figure it would only confuse the issue.
I was trying to stay away from radiation resistance because my experience of
the effect Bill ask about has been with small aircore inductors. But on
second thought
even those have Rr.

The smaller, the worse. It is not so much about the size of Rr, but
its relation (ratio) to Ohmic loss. For instance, a 1 meter loop
composed of #40 wire is going to be deaf and dumb at 80M, but you
might have a chance with 10cM hollow pipe with tight connections. Both
exhibit the same Rr, but the wire's Ohmic loss is clearly deadly in
comparison to it, than for the pipe's Ohmic loss. Rr in this band,
for this size, runs on the order of 0.0075 Ohms.

Why does the reistance go up near resonance?

I haven't seen that happen. However, for the same resistance, as you
approach resonance, the circulating currents climb, and loss is by the
square.

73's
Richard Clark, KB7QHC

Distributed capacitance effects Q?
 

"Richard Clark" wrote in message
...
On Sun, 29 Apr 2007 15:36:43 -0500, "amdx" wrote:

This is then a characteristic of the Capacitor called D (dissipation).
Any increase in current tied to loss immediately goes to the bottom
line of resistance - it is a square law relationship, after all.

So your saying yes, the thought experiment would show more loss,
but the loss is in the capacitor. The loss in a capacitor would be
dielectric
and loss in the plates right?

Hi Mike,

Depending upon construction, most assuredly. However, little loss is
found in dielectrics (unless you are using particularly crummy
examples). For bad dielectric, you can expects arcs and sparks
followed by carbon, and then catastrophic heat accumulation. Most
lost is in what is specified in ESR (effective series resistance)
which you have already identified as in the plates, but often more in
the leads and their connections to the plates. To pack in more
capacitance, the trend is for thinner plates for a given package
volume. You can guess where the resistance will rise there when the
circulating currents are see-sawing in that thin metal.

I gave you a little bit of a trick question when I ask,

The loss in a capacitor would be dielectric and loss in the plates right?

In my inductor the interwinding capacitance is made of a dielectric
(some type of insulation and air) and the plates (made by the wire).
The wire has more current because of that interwinding capacitance,
and as you say "loss is by the square".
Is my argument moving you at all?



(let's not get into radiation resistance right now)

Why not? Small loops suffer by comparison, and multi-turn loops even
more so.

I figure it would only confuse the issue.
I was trying to stay away from radiation resistance because my experience
of
the effect Bill ask about has been with small aircore inductors. But on
second thought
even those have Rr.

The smaller, the worse. It is not so much about the size of Rr, but
its relation (ratio) to Ohmic loss. For instance, a 1 meter loop
composed of #40 wire is going to be deaf and dumb at 80M, but you
might have a chance with 10cM hollow pipe with tight connections. Both
exhibit the same Rr, but the wire's Ohmic loss is clearly deadly in
comparison to it, than for the pipe's Ohmic loss. Rr in this band,
for this size, runs on the order of 0.0075 Ohms.

Why does the resistance go up near resonance?

I haven't seen that happen.
Try measureing the Q of an aircore coil close to it's self resonance
(or worse, at self resonance without an additional capacitor)
and then at half that frequency.

However, for the same resistance, as you
approach resonance, the circulating currents climb, and loss is by the
square.

I'm defining circulating currents as those that circulate between turns
and don't necessarily go through the capacitor used to resonate the coil.
Does that fit your definition as used in your paragraph above?

Thanks, Mike

Distributed capacitance effects Q?
 

Wimpie wrote:
The vertical coil behaves
almost as a quarter wave resonator, just a small top capacitor was
necessary.

Sounds like a 75m mobile bugcatcher antenna. :-)
--
73, Cecil http://www.w5dxp.com

Distributed capacitance effects Q?
 

Jim Kelley wrote:
I think this will interest you:
http://www.rhombus-ind.com/dlcat/app1_pas.pdf

Thanks very much, Jim.
--
73, Cecil http://www.w5dxp.com

Distributed capacitance effects Q?
 

On Sun, 29 Apr 2007 18:51:52 -0500, "amdx" wrote:

I gave you a little bit of a trick question when I ask,

The loss in a capacitor would be dielectric and loss in the plates right?

In my inductor the interwinding capacitance is made of a dielectric
(some type of insulation and air) and the plates (made by the wire).
The wire has more current because of that interwinding capacitance,
and as you say "loss is by the square".
Is my argument moving you at all?

Hi Mike,

I'm afraid that if you have expressed an argument, it was lost on me.

Why does the resistance go up near resonance?

I haven't seen that happen.
Try measureing the Q of an aircore coil close to it's self resonance
(or worse, at self resonance without an additional capacitor)
and then at half that frequency.

You have a moving target. Skin effect is shifting as you double/halve
the frequency. What does it mean to compare Q at so disparate
frequencies? Are you exploring an intellectual curiosity or trying to
remedy a defect in application?

However, for the same resistance, as you
approach resonance, the circulating currents climb, and loss is by the
square.

I'm defining circulating currents as those that circulate between turns
and don't necessarily go through the capacitor used to resonate the coil.
Does that fit your definition as used in your paragraph above?

Going between turns can be through a turn-to-turn capacitive coupling,
the magnetic coupling has already been discussed in regard to
increased skin effect due to proximity. Loss still remains the
province of resistance. Your best argument is that Capacitance
exacerbates loss, but it does not cause it.

73's
Richard Clark, KB7QHC

Distributed capacitance effects Q?
 

"Richard Clark" wrote in message
...
On Sun, 29 Apr 2007 18:51:52 -0500, "amdx" wrote:

I gave you a little bit of a trick question when I ask,

The loss in a capacitor would be dielectric and loss in the plates
right?

In my inductor the interwinding capacitance is made of a dielectric
(some type of insulation and air) and the plates (made by the wire).
The wire has more current because of that interwinding capacitance,
and as you say "loss is by the square".
Is my argument moving you at all?

Hi Mike,

I'm afraid that if you have expressed an argument, it was lost on me.

Why does the resistance go up near resonance?

I haven't seen that happen.
Try measureing the Q of an aircore coil close to it's self resonance
(or worse, at self resonance without an additional capacitor)
and then at half that frequency.

You have a moving target. Skin effect is shifting as you double/halve
the frequency. What does it mean to compare Q at so disparate
frequencies?

I agree that skin effect is just one more charactistic that needs to be
added to the mix.

Are you exploring an intellectual curiosity or trying to
remedy a defect in application?

No, I just have experienced the effect that Bill ask about and
gave my own pet theory about why it happens.
Now I'm looking for a little confirmation or where I went wrong.



However, for the same resistance, as you
approach resonance, the circulating currents climb, and loss is by the
square.

I'm defining circulating currents as those that circulate between
turns
and don't necessarily go through the capacitor used to resonate the coil.
Does that fit your definition as used in your paragraph above?

Going between turns can be through a turn-to-turn capacitive coupling,
the magnetic coupling has already been discussed in regard to
increased skin effect due to proximity.

Loss still remains the province of resistance.

Richard, That's like saying rain has water in it. No matter how many times
you say it,
I'm still going to agree with you.


Your best argument is that Capacitance exacerbates loss.

I would rephrase that as "interwinding capacitance exacerbates loss".

And with that, you have summed up my argument perfectly.

You have helped reduce my argument to 4 words.

Now, do you agree that interwinding capacitance will reduce Q?
(yes, I know it's the province of resistance)

Thanks, Mike