The reason for 1/4 wave length

[tekmann]

Hi dR-Green.......I will try this again as I have skipped too far ahead. If I have a primary wound coil and capacitor LC frequency tuned to 100 cps and a secondary wound coil that has a tuned resonant frequency or 400 cps ....and these two are used to make a tesla coil is this system considered 1/4 wave?

Bud

[dR-Green]

Hi dR-Green.......I will try this again as I have skipped too far ahead. If I have a primary wound coil and capacitor LC frequency tuned to 100 cps and a secondary wound coil that has a tuned resonant frequency or 400 cps ....and these two are used to make a tesla coil is this system considered 1/4 wave?

Bud

Hi Bud. A system is 1/4 wave when the electrical length of the conductor/resonator is 1/4 the wave length of the driving frequency.

λ = c/F

λ = wavelength in metres
c = speed of light in metres per second
F = frequency in cycles per second

The main component you should be working with is the frequency, not wire lengths. Even though the full wavelength of the wire in and of itself may be 400 CPS, it's being used in 1/4 wave mode so the full wavelength in terms of the particular piece of wire as a solitary object is irrelevant, because it's not a solitary object. The resonant frequency is still 100 CPS.

The luminal wavelength, or effective wavelength, is 4 times the conductor length, hence the inverse being 1/4. In resonance the conductor is effectively or electrically 4 times longer than its physical length. So there is no 400 CPS in relation to the system in question.

Like a radio, if you have a transmitter at 100 CPS and a receiver at 400 CPS you will receive nothing. The receiver must be tuned to a matching frequency in order to work.

[tekmann]

Hi Bud. A system is 1/4 wave when the electrical length of the conductor/resonator is 1/4 the wave length of the driving frequency.

λ = c/F

λ = wavelength in metres
c = speed of light in metres per second
F = frequency in cycles per second

The main component you should be working with is the frequency, not wire lengths. Even though the full wavelength of the wire in and of itself may be 400 CPS, it's being used in 1/4 wave mode so the full wavelength in terms of the particular piece of wire as a solitary object is irrelevant, because it's not a solitary object. The resonant frequency is still 100 CPS.

The luminal wavelength, or effective wavelength, is 4 times the conductor length, hence the inverse being 1/4. In resonance the conductor is effectively or electrically 4 times longer than its physical length. So there is no 400 CPS in relation to the system in question.

Like a radio, if you have a transmitter at 100 CPS and a receiver at 400 CPS you will receive nothing. The receiver must be tuned to a matching frequency in order to work.

OK, Lets try a different approach. If I were to build a tesla coil of any frequency....pick one......what would be the parameters of the primary and secondary so it would operate at 1/4 wave?

Bud

[artoj]

Not always Simple

Hi tekmann

dR-Green is absolutely correct, he explains it well, I thought this might help you.

Fp = 1/(2 x pi x sqrt( L x C )) = Frequency of Primary
Fs = 299792458 / ( WL x 4 ) = Frequency of secondary (this is only approx)

Fp = Fs this is the key

L = Induction of primary coil in Henries approx from 1 to 20 turns
C = Capacitance of Primary capacitor in Farads, high voltage type(5000-50000 volts)
WL = wire length of secondary in Meters, turns 20-2000, anywhere between awg16 to awg28, I generally use awg21 or awg25 or what is available.

This will get you started in the right direction, remember the secondary also has an inductance , this also needs to be balanced with a Top load capacitor, there is no simple equation on building Tesla coils. many other parameters need to be considered once you have the basic system tuned. The clearances between the primary and secondary are crucial to get a nice resonant action, keep it loose and not to close. Harmonics can also play a big role but that will just complicate your understanding somewhat.

Basically start with the coil former you want to use, then decide a frequency some where between 50000 hz to 500000 hz to 5000000 hz that will all depend on the number of turns. This will give you Fs, then work out your primary coil and cap until it matches the same frequency. I hope this helps regards Arto.

[dR-Green]

In basic terms

λ = c/F

λ = wavelength in metres
c = speed of light in metres per second
F = frequency in cycles per second

If F = 1000 kc

λ = 299792458/1000000 = 299.792458 Metres (luminal (full) wavelength)

λ/4 = 74.9481145 Metres (quarter wave conductor length)

Conductor length divided by desired number of turns = coil circumference

If number of turns = 20

74.9481145/20 = 3.747405725 Metres per turn

Diameter = 1.192... Metres

Coil height = 20% diameter = 0.2*1.192 = 0.2385... Metres

However, coil geometry will affect the effective propagation velocity so you will need to calculate and compensate if you want a certain frequency. See formulas for inductance and self capacitance

Coil Inductance Calculator - 66pacific.com







For given coil geometry

L = 721.83 µH
C = 83.44 pF

Given



F = 648.507 kc

This won't be 100% accurate with the measured frequency but should be close in free resonance.

I won't do any corrections because this is only for example purposes, but obviously if you want the original 1000 kc the coil should be reduced in size because the frequency will be too low. 648.507/1000 = 0.648507 so as a basic guide the conductor length should be approx 64% the original calculated length.

Going with 648.507 kc as the secondary resonant frequency, with 2 turn primary coil of 1.6cm height, same diameter as secondary

Primary L = 10.12 µH

Using the LC Constant to calculate required capacitance LC = 25330/f²

C = 5951 pF approx

However, one coil will also affect the characteristics of the other and this primary capacitance may lower the secondary frequency. Either way with one end of the secondary coil free and the other connected to a ground plane it will be in quarter wave resonance around that frequency.

http://www.energeticforum.com/eric-d...ompendium.html

[tekmann]

dR-Green- Thanks for being persistent with me. My perception of 1/4 wave was a relationship between the primary resonance and the secondary resonance. I see it is not that way now.

I just want to get this thing right in my mind. Hate not knowing why I am doing something the wrong way. Your explanation is very detailed and educational to me as well. We need more like you around. Thank you again!

Now I need time to digest this stuff.

Bud

[Ruphus]

This may also be helpful

Sondhauss tube[edit]

The Rijke tube operates with both ends open. However, a tube with one end closed will also generate sound from heat, if the closed end is very hot. Such a device is called a “Sondhauss tube”. The phenomenon was first observed by glassblowers and was first described in 1850 by the German physicist Karl Friedrich Julius Sondhauss (1815–1886).[8][9] Lord Rayleigh first explained the operation of the Sondhauss tube.[10]
The Sondhauss tube operates in a way that is basically similar to the Rijke tube: Initially, air moves towards the hot, closed end of the tube, where it's heated, so that the pressure at that end increases. The hot, higher-pressure air then flows from the closed end towards the cooler, open end of the tube. The air transfers its heat to the tube and cools. The air surges slightly beyond the open end of the tube, briefly compressing the atmosphere; the compression propagates through the atmosphere as a sound wave. The atmosphere then pushes the air back into the tube, and the cycle repeats. Unlike the Rijke tube, the Sondhauss tube does not require a steady flow of air through it, and whereas the Rijke tube acts as a half-wave resonator, the Sondhauss tube acts as a quarter-wave resonator.[11]
Like the Rijke tube, it was discovered that placing a porous heater — as well as a "stack" (a "plug" that is porous) — in the tube greatly increased the power and efficiency of the Sondhauss tube.[12][13] (In demonstration models, the tube can be heated externally and steel wool can serve as a stack.)[14]

From:
Rijke tube - Wikipedia, the free encyclopedia

[mikrovolt]

I agree with the comment here. Actually you are correct about Resonance but the wave also needs to be in phase. Maintain the phase angle.
With inductors the current lags the voltage. You could change the capacitance in which case the voltage lags. It is when the current peaks that you get little loss.
When the wave measured at A is not on top of the same wave measured at B. it is not in phase.

The sine wave on an oscilloscope represents voltage over time. The sine starts at zero, approaches max, down crosses zero, up approaches min, ends at zero. 1/4 wave works out nicely with this designation. Full wave has a feed point in the center of the coil like the Oudin coil. 3/4 5/8 1/8 could be messy.

It is better in achieving maximum current to think in terms of current and allow for the lag. Under load the phase angle changes. It is mismatch that contributes to loss in unnecessary wasted heat.

Dr Green chose 300 ohm as impedance. Now that he has a "given" he can work out a match between components. Today 50 ohm is often used today and wavelength are usually shorter. Also what we call DC can be pulsed DC, the wording changed over time and makes things confusing.
Here is a video supporting current lags voltage in an inductor which relates to 1/4 wave tesla.
There are more component waveforms we cannot easily identify but can utilize with Tesla devices.

Understand this clearly 2 videos. remember PEAK current has an important point in timing cycle.
1. Find the peak current that lags voltage.
2. Choose component values for impedance matching to keeps the wave in phase.
Back to Basics Tutorial: Voltage / Current in capacitors and inductors - YouTube
Wave phase and phase difference - YouTube

[Cycle]

Fp = 1/(2 x pi x sqrt( L x C )) = Frequency of Primary
Fs = 299792458 / ( WL x 4 ) = Frequency of secondary (this is only approx)

Fp = Fs this is the key

L = Induction of primary coil in Henries approx from 1 to 20 turns
C = Capacitance of Primary capacitor in Farads, high voltage type(5000-50000 volts)
WL = wire length of secondary in Meters, turns 20-2000, anywhere between awg16 to awg28, I generally use awg21 or awg25 or what is available.

Having no formal training in electrical theory or practice and being a mechanical engineer by trade, I'm afraid I'm forced to ask what may be Very Stupid Questions right now... please forgive me (and tell me) if this makes no sense whatsoever...

Reapplying the Tesla coil calculations above to an ordinary ignition coil, since the primary doesn't have any capacitor in parallel, would it be beneficial to figure out some way of applying a variable capacitance that would match with the firing rate of the coil at any given engine speed?

Would this not provide for "tuning" the coil to that specific firing "frequency", thereby increasing the transfer efficiency of power to the secondary and lessening the amount wasted as heat?

Would one also be required, if my assumptions above are correct, to do the same with the secondary?

[artoj]

Some Parameters

Hi Cycle,

Here is a little more to add in the equations (from my next book volume)
The most important is the Natural Frequency of all its parts.
These are all approximates
Measured can also mean calculated using formula

Ve = 299792458 x vf

vf = velocity factor relating to skin resistance, dielectric, heat etc usually 1 - 0.9

vp = pi / 2

Vt = Ve x vp = average Tesla longitudinal velocity

Ve = the particle velocity, radiation velocity

Vt = average longitudinal pressure wave velocity(a pressure differential wave)

Using Standard Radio light velocity (particle velocity) = Hertzian

Fp1 = Ve / ( WLp x 2 x Hmp ) = Frequency of Primary
Fp2 = 1/(2 x pi x sqrt( Lp x Cp )) = Frequency of Primary
Fs1 = Ve / ( WLs x 4 ) = Frequency of secondary
Fs2 = 1/(2 x pi x sqrt( Ls x Cs ))= Frequency of Secondary

Fp1 = Fp2 = Fs1 = Fs2 these are the keys to good performance

Using Tesla Longitudinal Velocity (pressure wave) = Non Hertzian

Fp1 = Vt / ( WLp x 2 x Hmp ) = Frequency of Primary
Fp2 = 1/(2 x pi x sqrt( Lp x Cp )) = Frequency of Primary
Fs1 = Vt / ( WLs x 4 ) = Frequency of secondary (a type of phase resonance)
Fs2 = 1/(2 x pi x sqrt( Ls x Cs ))= Frequency of Secondary

Fp1 = Fp2 = Fs1 = Fs2 these are the keys to even greater performance(using Vt)

Lpm = Measured Induction of primary air coil in Henries
Lpa = Induction of added wound on core/air coil, tunable
Lpb = Induction of metallic peripherals
Lpc = Mutual Induction coefficient of primary to secondary

Lp = Lpm + Lpa + Lpb + Lpc = Total Induction of Primary

Lsm = Measured Induction of Secondary air coil in Henries approx from 20 to 2000 turns
Lsa = Induction of added air core coil, tunable
Lsb = Induction of Top capacitor and metallic peripherals
Lsc = Mutual Induction coefficient of primary to secondary

Ls = Lsm + Lsa + Lsb + Lsc = Total Induction of Primary

Cpm = Measured Capacitance of Primary capacitor in Farads, high voltage type(5000-50000 volts)
Cpa = Capacitance added to Cpm for tuning, separate unit, safe distance
Cpb = distributed capacity of coil
Cpc = add stray capacity of nearby objects etc

Cp = Cpm + Cpa + Cpb + Cpc = Total Capacity of Primary

Csm = Measured Capacitance of Secondary capacitor in Farads, high voltage (100000-2000000 volts)
Csa = Top single terminal capacitor, generally a sphere or torus
Csb = distributed capacity of coil
Csc = add stray capacity of nearby walls roof etc
Csd = tunable plate, ball, cylinder etc, acting near Csa

Cs = Csm + Csa + Csb + Csc + Csd = Total Capacity of Secondary

WLp = wire length of primary in Meters, approx from 1 to 20 turns
WLs = wire length of secondary in Meters, turns 20-2000, anywhere between awg16 to awg28, I generally use awg21 or awg25 or what is available.

Hmp = Harmonic number for primary half wave, generally around a 100, from 20 to 2000

Also another important ratio is:

Lp x Cp = Ls x Cs

in term of reactance

XLp = XCp
XLs = XCs

The power in a Tesla resonating coil is massive, if the top capacitor breaks down, then this is considered a loss, but it is the only indicator of the actual voltage present. Good Tesla coils do not radiate and do not spark, they drive a longitudinal pressure wave a half wave length distant from the ground location. Forget about what they taught you in the Einsteinian physics class about propagation of light and do the experiments yourself, without bias. Eric Dollard has given us the equations and transmitted his understanding and his insight from Tesla and others, it is up to each one of to add and help define a new paradigm of FTL communication, Tesla style.

This is only a brief description, it can all be related to mechanical and acoustic equations. I am not an Engineer, I am an Artist, Author and a practical experimenter, Regards Arto.

[Guruji]

1/4 wave

I saw a doc about Tesla flying saucer and he mentioned that to build an aircraft with tesla coils one have to be 1/4 wavelenght.