resonance coils

[Murlin]

I had a question on winding coils that need to be tuned to each other.

If your Secondary coil is suppose to be 25% shorter than the Primary in order to be in tune,
would it matter you ended up with a partial turn on the last coil in order to keep the right length of wires?


Thanks,


Murlin

[cody]

I would design a tuning method for one or both of the coils, that way you dont have to be exact with coil length. Im not sure exactly what your working on but 25% shorter sounds strange, ideally the coils should be the same length or multiples to be in tune, of course thats not considering adding capacitance. Either way, I would add a way to vary capacitance or inductance and just dial it in exactly form there.

[Murlin]

I would design a tuning method for one or both of the coils, that way you dont have to be exact with coil length. Im not sure exactly what your working on but 25% shorter sounds strange, ideally the coils should be the same length or multiples to be in tune, of course thats not considering adding capacitance. Either way, I would add a way to vary capacitance or inductance and just dial it in exactly form there.

If the tuning method is set and not changeable and it's output is 100
volts with a frequency of 20 khz and mil amps and is applied to a coil
of 5 turns. Then by inductance is picked up by another smaller od coil
with 10 and 1/2 turns what will be the total voltage of the second coil?
200 volts or 200 plus 10 volts or?


Lets assume the only way you have to tune the two coils to resonance is by wire length and number of coils.


I guess what I am asking is if the extra partial coil would add to the total voltage of the inductance coil or does it have to have to end up to be an exact number of turns so the od of the winding jig has to be exact?


Thanks,

Murlin

[cody]

I believe it should add to the total voltage so it would go like this

Primary- 100V to 5 turns
100/5 = 20V per turn

Secondary 10.5 turns
20V X 10.5 = 210V output

So it should put out around 210V. But if your talking about resonance than of course the extra length is going to make some difference as any change in wire length, inductance, capacitance will effect the resonant frequency.

[Murlin]

Thanks for the replies cody. Have a great day!


Murlin

[Harvey]

Transformer Formula:

Es = Ep * ns / np

Es = Secondary EMF (voltage)
Ep = Primary EMF
ns = number of secondary windings
np = number of primary windings


Reactance Formulas:

Capacitive Reactance:

Xc = 1 / 2 π f C
π = 3.14159
f = frequency in Hertz
C = capacitance in Farads

Inductive Reactance:

XL = 2 π f L
π = 3.14159
f = frequency in Hertz
L = inductance in Henries

Resonance:
Resonance occurs when Xc = XL.
The frequency for resonance can be determined by:
f = 1 / 2 π √LC

Inductance:
For a single layer air core coil:

L = r˛N˛ / 9r + 10l

L = microhenries

r = radius of the coil in inches
N = number of turns
l = Length of the coil in inches

To determine the number of turns for a known inductance:
N = √(L(9r + 10l) / r˛

=============================================

From this you can see that the length of the coil (not the wire, but the actual coil) affects the inductance. This means that you can change the spacing between windings and alter the inductance. Likewise, the size of the coil diameter (2r) also affects the inductance. So these things are important as is the number of turns. As you might imagine, you can have half a turn, and still be off because of the insulation coating on the windings may accumulate to a longer coil than you calculated. They all interplay. Also, every coil has a self capacitance, because each winding acts as a capacitor plate to the one next to it. The capacitance is usually very very small but it does add to the ability for a coil to store a capacitive charge at one end of the wire when the magnetic field is collapsed, and this allows the coil to resonate all on its own at certain frequencies.

In the old days when TV tuners were made of coils and capacitors, we would tune them by stretching or compressing the coils to change their length and thus change their inductance, which in turn changes the inductive reactance, which would bring the two into resonance. Most tuners had a variable capacitor in series with the selector capacitor for fine tuning (it was a dial behind the main channel selector switch).

When you say your secondary needs to be 25% shorter to be in tune, that could be taken a number of ways.

One meaning could be the length of the coil as I have mentioned above.

Another way could mean that the coil is being used as a loading coil on an antenna where the overall length of the antenna requires the load coil to be 25% that of the primary transmission coil. One application would be where the transmission antenna is a full wave antenna and the receiver is a quarter wave antenna.

So without the actual dimensions of your coils it is difficult to tell if that half turn will make a significant difference or not. From a voltage perspective in a transformer arrangement it amounts to a 10V differential for the turns ratio you posted. But from a resonance point of view determining the self capacitance of each coil is no trivial matter.

[Murlin]

Thank you Harvey for that detailed explanation.

I was just doing some reading in the Donald Smith thread and never having experimented with resonance coils before myself, I sought some guidance from those who were.

Resonance does sound tricky indeed...but your knowledge has given me some place to start.

Thanks allot


Murlin

[Xenomorph]

Thank you Harvey for that detailed explanation.

I was just doing some reading in the Donald Smith thread and never having experimented with resonance coils before myself, I sought some guidance from those who were.

Resonance does sound tricky indeed...but your knowledge has given me some place to start.

Thanks allot


Murlin

Donald Smith ???
Calculate a quarter wavelength of 20kHz before you build anything

[Harvey]

Donald Smith ???
Calculate a quarter wavelength of 20kHz before you build anything

Is that about 3.75 km ?

[wings]

Is that about 3.75 km ?

try EH antenna very different from "Hertz theory"

wide band much less dimensions

EH-Antenna

EH Antenna Systems

[Harvey]

Yes the EH and the H-Z are interesting Radio Applications.

I think Murlin is working on a Don Smith application though?

[Murlin]

Yes the EH and the H-Z are interesting Radio Applications.

I think Murlin is working on a Don Smith application though?

Oh Darn I have been found out

Yes... just doing research though...must finish my commutator tesla switch before I get too deep into his stuff though...

regards,

Murlin

[wings]

Yes the EH and the H-Z are interesting Radio Applications.

I think Murlin is working on a Don Smith application though?

from
EH antennas:

"On 13/7/2005, because of a solar storm, all the bands were silent with normal antennas, but my EH were very noisy: the noise level was S5 and those “fritting pan” signal were S6 !!! …

Normally the EH are much more silent than the standard dipoles !!!!"

...
om




Any idea about the reason ?

[Xenomorph]

from
EH antennas:

"On 13/7/2005, because of a solar storm, all the bands were silent with normal antennas, but my EH were very noisy: the noise level was S5 and those “fritting pan” signal were S6 !!! …

Normally the EH are much more silent than the standard dipoles !!!!"

...
om




Any idea about the reason ?

Solar storms are likely to emit all kinds of radiation including
not only Hertzian waves but strong longitudinal energy as well.
This will manifest itself as "noise" in the antenna.
(See Meyl etc.)