US2206238A - Oscillatory circuits - Google Patents

Description

OSCILLATORY CIRCUIT Sv Filed March 20, 1-93'7 by` /YZWN/ lflvrlzey Patented July 2, 1940 i UNITED sTATEs a PATENT foFEicE 2,206,238 y oscrLLAronY CIRCUITS Hans Rochow, Berlin-Lichterfelde, Germany, assignor to C. Lorena Aktiengesellschaft, Berlin- E Tempelhof, Lorenzweg, Germany, a company a Application March 20,

1937, Serial No. 132,050

In Germany April 4, 1936 p however, especially if arrangements for very high l frequencies are concerned, difliculties arise `l through a frequency change which is independent ol the temperature of the surrounding medium. This special frequency change may occur for in'- stance with discharge tubes of the kind having a glowing-cathode and one or more additional .15 electrodes, being caused here by the inter-electrode capacities varying when the `tube is heated up. Such capacity variation will cause a frequency change of the oscillatory circuits in which tubes of this kind `are included. 20 The invention has for its object to avoid these diflioulties and to such end provides for compensating the said special frequency change in `a peculiar manner, as will be understood from the following description and be particularly 25 pointed out in the appended claim, reference being had to the accompanying drawing that shows an example of a circuit arrangement as provided by the invention.

The `example illustrated is a feed-back connec- 30 tion and comprises a tube E that has three elec-` trodes one of which is a glowing-cathode C.

When heating up this tube the inter-electrode capacities, that is, the capacities between cathode C, grid and anode, undergo` variation. In the 35case of an indirectly `heated tube, for example,

this variation is such that after a certain time,

. for instance` 20 minutes, a definite value of the inter-electrode capacities is reached.

In the example here disclosed the variation in the interelectrode capacities is compensated by a variable additional capacity connected in parallel with the inter-electrode capacities and cone stituted by a condenser that consists of a metal plate A and a birnetallic strip or spring B. Plate A is connected to the anode, as shown. Spring` B is heated by a coil H connected in parallel with cathode C. Hereby the distance between A and B and thus the additional capacity connected in parallel` with the inter-electrode capacities is so varied that a variation of these is compensated and that therefore a frequency change of the oscillatory circuit pertaining to tube E will not occur. Spring B is disposed in a jacket or any other casing or envelopment J made of a material which is a non-conductor of heat. By this means spring B is given a time constant which is equal to that of tube E, that is to say, the final capacity value of spring B is' reached in the same time as that of tube E,

Whatis claimed is: l An oscillatory circuit including a glowing cathode tube and means associated therewith for opposing frequency changes resulting from changes in the constants of said tube during operation thereof comprising a condenser connected directly between the anode and cathode of said tube, a bi-rnetallic strip having an electrie heating element connected in parallel with `said cathode for varying the capacity of said condenser and a heat insulating jacket surrounding 'said strip and saidheating element, said jacket being so proportioned that the final value of capacity of the said condenser as controlled by said loi-metallic strip is reached at the` same time as the fnalcapacity of said tube upon heating up of said circuit.

HANS ROCHOW.

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