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It can be seen that a fixed radfiator hasd a primary frequency and
then some harmonic frequencies. The spacing and the resonant points of an antenna resides in the amount of resistance in the cuircuit from zero upto a critical point as with a tank circuit. This resistance value has the action of bringing the radiator vibrational amplitude to zero where it then takes of to a diminishing value compared to other componenents in the circuit to the point that where the radiator is resonant the contained resistance has negnigable effect. Thus one can make a folded dipole with a variable resistance in the radfiating circuit such that the main resonant point can be determined as well as the spacing between the harmonic frequencies. In addition, if the radiator consists of increased induntance designs such as contra windings then the distance between the resonance point and the harmonic points begin to decrease. Thus using the above one can now make a all band antenna where the resonance points line up with the desired frequencies. An easy way to accomplish this is to wind wire on a dielectris from end to end and back again several times until one has wound at least two wave lengths on the former and then feeding the arrangement at the beginning and ending wire points. Using a mfj 259 one can then determine the spacings of the resonant point by stretching the windins as well as adding the required variable resister. Note. the resistance absorbs the energy between resonance points and diminishes in effect as the point of resonance is aproached. For more understanding of the radiation format of radiators review the circumstances of voltage overshoot with respect to tank circuits The above will provide an alternate discussion thread that will take away the current tunnel vision aproach with respect to "black boxes" and bring the newsgroup back to the advancement of antenna techniques if it is that that peeks one's interests. By the way, it is the ELECTROMAGNETIC field that launches the particles from the radiating surface and it is the MECHANICAL REACTIVE FORCE that provides the mechanical resonance of the radiator WHICH JOINS THE THEORIES OF NEWTON AND . MAXWELL that Einstein struggled for in vain. For those that feel that mechanical laws of Newton cannot be used with respech to electrical subjects( ala Roy) here is a chance for you to prove your point. Regards Art Unwin, a limey no less |
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