Inductance of a solid disk
 

I am looking for a formula giving the inductance of a solid disk for a
known diam/material/thickness...

Any idea?

Thanks for your hels de Pierre VE2PID

Inductance of a solid disk
 

On Dec 27, 9:35*am, ve2pid wrote:
I am looking for a formula giving the inductance of a solid disk for a
known diam/material/thickness...

Any idea?

Thanks for your hels de Pierre VE2PID

What, exactly, do you mean by "the inductance of a solid disk"? How
do you connect to the disk? Are your connection points on opposite
ends of a diameter across the disk, or along its axis from the center
of one face to the center of the face on the opposite side -- or
perhaps some other connection? With a wire (formed into any shape),
it's reasonable to assume it's the inductance measured between the two
ends of the wire. For a disk, it's not obvious to me.

Cheers,
Tom

Inductance of a solid disk
 

"ve2pid" wrote in message
...
I am looking for a formula giving the inductance of a solid disk for a
known diam/material/thickness...

Any idea?

Thanks for your hels de Pierre VE2PID

Hi Pierre

Can you measure or estimate the inductive reactance of the disk?

Jerry KD6JDJ

Inductance of a solid disk
 

ve2pid wrote:
I am looking for a formula giving the inductance of a solid disk for a
known diam/material/thickness...

Any idea?

Thanks for your hels de Pierre VE2PID

I am taking it, you mean when it is used as a radiating element in the
antennas' construction. Such as a few charts which can be found around
which predict the inductance of a wire radiating element -- I have never
seen, either software or charts/tables/formulas, to predict such ...
perhaps EZNEC or MMANA-GAL could be used for such a purpose--I honestly
don't know ... Roy would know ... perhaps Cecil is aware of something?

Or, do you mean something else?

Regards,
JS

Inductance of a solid disk
 

"Jerry" wrote in message
...

"ve2pid" wrote in message
...
I am looking for a formula giving the inductance of a solid disk for a
known diam/material/thickness...

Any idea?

Thanks for your hels de Pierre VE2PID

Hi Pierre

Can you measure or estimate the inductive reactance of the disk?

Jerry KD6JDJ

try this:
http://www.consultrsr.com/resources/eis/induct5.htm

Inductance of a solid disk
 

John Smith wrote:
... perhaps Cecil is aware of something?

I'm wondering if he means "reactance" instead of
inductance. The reactance to ground is capacitive
for a solid disk.
--
73, Cecil http://www.w5dxp.com

Inductance of a solid disk
 

On 28 déc, 09:52, Cecil Moore wrote:
John Smith wrote:
*... perhaps Cecil is aware of something?

I'm wondering if he means "reactance" instead of
inductance. The reactance to ground is capacitive
for a solid disk.
--
73, Cecil *http://www.w5dxp.com

Hello to all,

The context is this: We are discuting about capacitance hats.. It
seems that the name is confusing, since it adds inductance instead of
capacitance to an antenna.

So, since a solid disk adds inductance (the resonnant freq of the
antenna drops), we are looking for a formula to evaluate that
inductance (and then inductive reactance)..

BTW, why don't we use the name 'inductive hat'...??

Inductance of a solid disk
 

"ve2pid" wrote in message
...
The context is this: We are discuting about capacitance hats.. It
seems that the name is confusing, since it adds inductance instead of
capacitance to an antenna.

So, since a solid disk adds inductance (the resonnant freq of the
antenna drops), we are looking for a formula to evaluate that
inductance (and then inductive reactance)..

BTW, why don't we use the name 'inductive hat'...??

adding capacitance also lowers the resonant frequency. remember, the
capacitive hat is not adding capacitance in series with the feedpoint, it is
adding to the self capacitance and capacitance to the ground.

Inductance of a solid disk
 

Cecil Moore wrote:
John Smith wrote:
... perhaps Cecil is aware of something?

I'm wondering if he means "reactance" instead of
inductance. The reactance to ground is capacitive
for a solid disk.

I see what you mean, the disk DOES contain inductive reactance (I don't
even know how to begin to compute its' value, however), and, as per your
post, the capacitive reactance to ground is an important point to consider.

I hope he posts back, with more definition, he posed a question to catch
my interest; although, you are best to provide us with real information.

Regards,
JS

Inductance of a solid disk
 

ve2pid wrote:
On 28 déc, 09:52, Cecil Moore wrote:
John Smith wrote:
... perhaps Cecil is aware of something?
I'm wondering if he means "reactance" instead of
inductance. The reactance to ground is capacitive
for a solid disk.
--
73, Cecil http://www.w5dxp.com

Hello to all,

The context is this: We are discuting about capacitance hats.. It
seems that the name is confusing, since it adds inductance instead of
capacitance to an antenna.

So, since a solid disk adds inductance (the resonnant freq of the
antenna drops), we are looking for a formula to evaluate that
inductance (and then inductive reactance)..

BTW, why don't we use the name 'inductive hat'...??

Sorry, when replying to Cecil, I missed this post ... thanks for posting
back. Yes, in the scope of my knowledge, it WOULD, indeed, add
inductive reactance to the antenna, however, as Cecil seemed to imply,
the effect of the capacitive reactance, you are also adding with the
disk, overwhelms the inductive ... however, Cecils' input will be the
correct one; consider mine a guess.

Regards,
JS

Inductance of a solid disk
 

On Dec 27, 1:58*pm, K7ITM wrote:
On Dec 27, 9:35*am, ve2pid wrote:

I am looking for a formula giving the inductance of a solid disk for a
known diam/material/thickness...

Any idea?

Thanks for your hels de Pierre VE2PID

What, exactly, do you mean by "the inductance of a solid disk"? *How
do you connect to the disk? *Are your connection points on opposite
ends of a diameter across the disk, or along its axis from the center
of one face to the center of the face on the opposite side -- or
perhaps some other connection? *With a wire (formed into any shape),
it's reasonable to assume it's the inductance measured between the two
ends of the wire. *For a disk, it's not obvious to me.

Cheers,
Tom

I would think if you measure the inductance from the center of one
side of the disk to the cnter of the other side of it would be like a
large number of hair pins in parallel.
I tried building a collinear antenna around this idea with the
vertical part of the antenna a solid piece of CU tubing with the disk
place at .5wl points. The problem was that the disc act as capacity
hat.


Jimmie

Inductance of a solid disk
 

On Dec 28, 8:37*am, ve2pid wrote:
On 28 déc, 09:52, Cecil Moore wrote:

John Smith wrote:
*... perhaps Cecil is aware of something?

I'm wondering if he means "reactance" instead of
inductance. The reactance to ground is capacitive
for a solid disk.
--
73, Cecil *http://www.w5dxp.com

Hello to all,

The context is this: We are discuting about capacitance hats.. It
seems that the name is confusing, since it adds inductance instead of
capacitance to an antenna.

So, since a solid disk adds inductance (the resonnant freq of the
antenna drops), we are looking for a formula to evaluate that
inductance (and then inductive reactance)..

BTW, why don't we use the name 'inductive hat'...??

Remember, the current where a capacitive hat is located in the antenna
(at the end of an element) is relatively low. Adding inductance there
has relatively little effect. On the other hand, that's just where
even small amounts of capacitance have a fairly large effect.

Consider too that if the environment is symmetric, such as with a
vertical over a flat, uniform (or radially symmetrical) ground, with a
top had that's also radially symmetrical, the current in that top hat
will be radial and symmetrical, and will for all practical purposes
cancel out with respect to radiation from the top hat itself.

Look at the change in current distribution along the antenna
conductor, and compare the situation with and without top hats. It
should become immediately obvious what the advantage of a top hat is.
I would certainly call the effect "capacitive" and not "inductive."

It may also be instructive to look up design notes about VLF
transmitting antennas. Very large non-radiating "top hat" structures
are commonly used in them to get reasonable efficiency. I think
you'll be able to find examples of this sort of design from as far
back as a hundred years ago. The folks I've talked with about the
design of one such local antenna system are quite clear about the top
wires' role in changing the current distribution in the vertical
element, but not contributing directly to the radiation in any
significant way.

Adios,
Tom