Hollmann’s famous books: Physik und Technik der ultrakurzen Wellen, Band 1 & 2, were of its kind, probably, the most comprehensive publications of 1936.
Physics and technology of ultra shortwaves, volume 1 and 2
Hollmann’s books cover a wide variety of topics. Some of it concerning long forgotten themes, its duplication would, however, not justify the consumption of our restricted web space. I have, therefore, selected some subjects which I consider being intriguing.
Righi’s so-called "oscillator" or spark-gap is not easy to understand. Like most spark-gaps, the energy is stored in a capacitive system, consisting of two sections, which is being charged with a very high voltage across its two conducting sections. When the electric charge (voltage) reaches a certain level, the air will become ionised and a plasma is formed, which is then conducting the equalising currents. Due to inductance in the arrangement, a damped current is flowing in alternating directions. The physical system dimensions determine the frequency of the radiated electromagnetic waves .
The total energy stored in such a system (just when the current starts flowing) obeys to:
E = ½ C.U² (joule)
Ultra high frequency spark-gap devices (including the linked antenna radiators) may be estimated to have a capacitance of 5 - 20 pF (between 5 to 20 . 10-12 farad). It is evident, that sufficient energy has to be delivered by the high voltage component U. Practically, being between 50 - 150 kV.
Please, regard also my paper on Hülsmeyer (Radar I)
Righi placed his spark-gap inside a container (envelope) filled with a dielectric substance consisting of paraffin or petroleum. Consequently, though omitting the proof, this measure increased the voltage necessary to voltage breakdown (and increasing the system capacitance, as well). Hence, increasing U².
Righi "oscillators" were often employed without any additional antenna wires. The length of the spark, determines the wave length. Therefore, it transmitted in the SHF regions of a few centimetres only. However, by doing so, reducing the distance of communication to about a hundred metres only. Taking into account, that the insensitive coherer detector was the only device available to determine the existence of wireless signals.
Consider Hollmann text (Volume 1, p. 9-10): Righischer Oszillator (= oscillator)
Synphase circuitry (Volume 1, p. 49 - 50)
Mehrfach-Gleichtaktsender, Holborn - Generator, Relaxtionsschwingung, Gleichtaktanordnung nach Hollmann
Ultrakurzwellendetektor (diode) (Hollmann volume 2, p. 4)
Ultra shortwave semi-conductor diode. Interesting is, that this publication may indicate, that in Britain one could have noticed this quite modern miniature whisker type diode construction, before the start of WW 2.
Sägezahnantenne (sawtooth antenna) type Chireix - Mesny
The Germans used this antenna type for their mobile UHF communication link apparatus: Elster DMG 2T (about 475 - 525 MHz)
benachbarter Halbwellen vektoriell ..., Horizontalkomponenten,.. Phasenrichtigkeit.., in Frankreich vielfach ...
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