Hertz experiment
Antoine, Fri Feb 20 2009, 10:47AMHi everyone, I am new in this forum.
-First of all, please be lenient with my English, I am french and when it deals with foreign languages, french people are really terrible... -
I am intersted in the Hertz experiment. I am sure the people in this forum who make radios from scratch know this expriment, for the other : http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture6/hertz/Hertz_exp.html
I have read many threads on this forum that deal with related subjects but never managed to find the information I wanted.
I would like to make this experiment for a one of the numerous examinations needed to earn the privilege of being admitted in a pretigious science french high school (an equivalent of the M.I.T).
I already have a flyback running at 30kv and a small Marx Generator I made a year ago that can deliver about 150kv to power the whole thing.
The problem I have is I don't have enough precise figures about this experiment... I juste wanted to know if anyone of you knew where I could find more information about the experiment itself.
I know how to make all the calculus to know the intensity, frequency etc. of an oscillation dipolar.. (learned it at school).
But yet, I would need more information to solve, for exemple those several problems:
-I would like to calculate the frequency of the wave and its intensity given the dimensions avec the balls and the space between them, which i can't do because it is not a "standard" dipolar.
-I don't know how to design the small receptor ring so that It has a frequency equal to the emitting frequency.
Thank you very much for your help, and please don't hesitate to ask for further details, because I know my english is barely understandable.
[Edit: Fixed link]
Re: Hertz experiment
Proud Mary, Fri Feb 20 2009, 12:51PM
Hello Antoine! Comment ca va?
I can not open your link, but I can see Hertz's apparatus in my mind.
The receiver I would call a 'vertically polarized single turn magnetic loop antenna.'
The length of such a loop, in feet, is given by 1005/MHz.
The gain of such a loop is about 1.9 db compared with a dipole (2 db if the circle were perfect!)
The impedance - Z - across the gap is about 102 ohms.
The Q of a small loop is obviously high, and the antenna can be expected to respond to all sorts of harmonics in addition to the fundamental frequency, fo.
Save yourself the pain, and use the loop antenna calculator here:
Attention: Hertz had to view the spark gap with a microscope, because of the very small nature of the sparks. Modern reproductions of Hertz's resonator usually put a neon bulb across the spark gap, to make the discharge more visible.
Proud Mary, Fri Feb 20 2009, 12:51PM
Hello Antoine! Comment ca va?
I can not open your link, but I can see Hertz's apparatus in my mind.
The receiver I would call a 'vertically polarized single turn magnetic loop antenna.'
The length of such a loop, in feet, is given by 1005/MHz.
The gain of such a loop is about 1.9 db compared with a dipole (2 db if the circle were perfect!)
The impedance - Z - across the gap is about 102 ohms.
The Q of a small loop is obviously high, and the antenna can be expected to respond to all sorts of harmonics in addition to the fundamental frequency, fo.
Save yourself the pain, and use the loop antenna calculator here:
Attention: Hertz had to view the spark gap with a microscope, because of the very small nature of the sparks. Modern reproductions of Hertz's resonator usually put a neon bulb across the spark gap, to make the discharge more visible.
Re: Hertz experiment
Steve Conner, Fri Feb 20 2009, 02:16PM
Oh la la, c'est magnifique.
L'experience de Hertz doit fonctionner aussi bien avec un dipole pour l'emetteur et une boucle pour le recepteur. Avec deux dipoles identiques, ca ne va pas: l'antenne de reception doit presenter un court-circuit aux basses frequences, pour assurer que votre lampe neon s'illumine a cause des veritables ondes Hertziennes, et non pas de l'induction electrostatique.
Phew.
Steve Conner, Fri Feb 20 2009, 02:16PM
Oh la la, c'est magnifique.
L'experience de Hertz doit fonctionner aussi bien avec un dipole pour l'emetteur et une boucle pour le recepteur. Avec deux dipoles identiques, ca ne va pas: l'antenne de reception doit presenter un court-circuit aux basses frequences, pour assurer que votre lampe neon s'illumine a cause des veritables ondes Hertziennes, et non pas de l'induction electrostatique.
Phew.
Re: Hertz experiment
Proud Mary, Fri Feb 20 2009, 03:12PM
Antoine, I would choose a neon bulb like this:
It is so small it will not damp so much the veritables ondes Hertziennes as Steve calls them!
I guess that the capacitance between the two electrodes in this type of neon bulb is less than 0.5pF, so it will not lower the frequency of oscillation of your Hertz resonator ring very much - until conduction occurs.
Proud Mary, Fri Feb 20 2009, 03:12PM
Antoine, I would choose a neon bulb like this:
It is so small it will not damp so much the veritables ondes Hertziennes as Steve calls them!
I guess that the capacitance between the two electrodes in this type of neon bulb is less than 0.5pF, so it will not lower the frequency of oscillation of your Hertz resonator ring very much - until conduction occurs.
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