US2238268A - Reflecting antenna for radio beacons - Google Patents

Description

April 15, 1941. w KAUTTEYR 2,238,268

REFLECTING ANTENNA FOR RADIO BEACONS Filed Dec. 27, 1959 Patented Apr. 15, 1941 TENT ()FFICE.

REFLECTING ANTENNA FOR RADIO BEAC'ONS Wolfgang Kautter, Berlin, Germany, assignor to O. Lorenz Aktiengesellschaft, Berlin-Tempelhof, Lorenzweg, Germany, a company Application December 27, 1939, Serial No. 311,081 In Germany January 7, 1939 1 Claim.

where a: is more or less small with respect to number one. With such small capacity variations it will sometimes be difiicult to produce strong effects on the reflecting antennae or dipoles.

The present invention is an improvement upon arrangements of this kind and consists in certain features of novelty which will appear from the following description, reference being had to the accompanying drawing in which Fig. 1 is a diagrammatic representation showing an embodiment of the invention, while Fig. 2 is a so-called. substitute or equivalent diagram that serves to explain the principle on which the invention is based.

As will be seen from Fig. 1 parallel as well as series resonance of an oscillatory circuit arranged between conductors constituting a dipole D are used. The operative means of this circuit are so calculated that the rotary condenser AC when in the position where its capacity is Co just produces series resonance with coil L of the oscillatory circuit, dipole D thus being perfectly free to oscillate. When the rotary condenser is in the position where its capacity is CO+AC it acts to render the inductive branch L/Z, L/2 so intensely inductive that this branch will cooperate in parallel resonance with condenser Cp of the oscillatory circuit, so as to constitute a high ohmic resistance interposed between the terminals 11, a of the dipole conductors. The magnitude Rres, Fig. 2, of this resistance depends in part upon the attenuation d of the circuit L, Cp and may therefore be varied by means of ohmic resistances, such as the variable resistance R, so that the attenuation acting on dipole D may be adjusted without condenser AC requiring to be varied in any respect. In the case of high frequency the electromotive force E for the dipole is applied to Rres over the radiation resistance Rs, the dipole current hence being for the series resonant condition and for the parallel resonant condition. The modulation degree thus is a= 8+ T8| Consequently Rres must be made great with respect to Rs in case the dipole is to be afiected intensely. The resonance resistance Rm is determined as follows:

In the event of parallel resonance the resistance of the inductive bran-ch L/2, L/2 is For instance, if c'..=20-10 farads while C';,=200-10 farads then x=10%. The resonance resistance then is l. .d we, d Hence it will be convenient to minimize Co as far as possible. For short waves the circuit attenuation d is and still less. Thus, with a frequency of 100 megacycles per second it follows that Rres=1600 ohms. This resistance is great over the radiation resistance, which is about ohms. Therefore, even in the case of high frequencies the novel arrangement is suitable for modulation.

What is claimed is:

A modulating device for varying the reradiation effect of a radiation energized reflector dipole comprising an oscillatory circuit connected between the dipole parts, and a variable condenser coupled to said circuit to tune said circuit alternately to parallel resonance and to series resonance at the operating frequency dependent upon the adjustment of said condenser.

WOLFGANG KAUI'TER.

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