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.
Subject 1
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)
Subject 2
Synphase circuitry (Volume 1, p. 49 - 50)
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Subject 3
Ultrakurzwellendetektor (diode) (Hollmann volume 2, p. 4)
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Subject 4
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)
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Back to: Handbooks papers and product information
Back to: Elster DMG2T
