US2128750A - Ultra-short wave receiving apparatus - Google Patents

Description

Aug. 30, 1938. w. KRIEBEL ULTRA-SHORT WAVE REEJEIVING APPARATUS Filed Oct. 28, 1937 INVENTOR.

A El? KRIEBEL ATTOI VEY.

Patented Aug. 30, 1938 UNITED STATES PATENT orncr:

ULTRA- SHORT WAVE RECEIVING APPA- RATUS ration of Germany Application October 28, 1937, Serial No. 171,443

Germany S 3 Claims.

The present invention relates to a tube detector for receiving ultra-short waves. This detector is more sensitive than a bolometer and exhibits above all a uniform response.

The inventive idea is as follows:-

The emission source or cathode of a discharge tube, e. g. of a diode, is directly supplied with the high-frequency receiving current so that heating or additional heating is effected thereby.

10 As the emission of a cathode, so long as the ap plied plate voltage by far exceeds the saturation voltage, greatly depends on the heating, relatively small variations of the receiving currents may be made perceptible in this manner. E. g. a heat- 15 ing current variation by 1% yields an emission variation of about 20%. One reason why the plate voltage must exceed saturation voltage is to prevent space charge between the cathode and the plate.

A relatively simple arrangement results, if a diode is used as receiving tube and one dipole half each is attached to the ends of the straight cathode.

As the filament energy consumption varies for a given resistance of the spot to be heated with the square of the current the cathode, preferably, is initially heated by a constant but adjustable, as may be required, direct current and the received high-frequency oscillations are used only to render an additional heating. To avoid the high-frequency leaking off through the heating current leads, one may either design the emissive spot to be very small so that it prac= tically lies only in the voltage node of the dipole,

w or tune the heating current leads by means of a metal slider which is insulated from the heating current leads and is sliding on them. Further, one may shape the emissive spot to an indirectly heated cathode. In this case the heater is shaped to run bifilarly within the emission layer support and the lead-in wires are placed exactly at the voltage node. With extraordinary short waves it may occur that the small dipole halves intended to collect the radiation lie at the greater part within the vacuum vessel or in the wall of the tube. In such case it is recommendable to make the radiation collector equal to'an odd number of half wave lengths, e. g. 3/2)\, and to arrange that one voltage node each lies in the centre or the emissive spot and at the seals through the wall of the vessel respectively; or, alternately, one mounts the tuned dipoles, i. e. dipole designed to have a certain length, together with the emission source within the vacuum. vessel.

In the Figs. 1 to 3 of the accompanying draweptember 2, 1936 ing embodiments of the invention are shown. Therein is designated by:

I the plate of a directly heated diode 9; 2 and 3 a dipole joined to the terminals of the filament 4 (2 and 3 are tuned to M2 of the decimeter wave to be received); 5 a variable resistance for adjusting the heating current supplied by the heating battery 6 and thereby at the same time the emission of the filament 4 to the most favourable value, I an indicator, e. g. a head phone, 8 the plate battery. The filament consists of a tungsten-, thoriated or oxide-coated wire. The oxide-coated filament, e. g., is made of a core of platinum or a platinum-iridium alloy to which oxides of the alkaline earth metals, as calcium-, strontiumor barium-oxide, together with various admixtures are pasted, fused or sintered on.

The performance of the device is as follows:-

The modulated high-frequency, which oscillates on the dipole together with the inserted filament, varies the heating and thereby the emission'of the filament in time with the modulating amplitude. The emission variations produce plate current variations in the plate circuit, which are listened to by means of head phones either directly or through an amplifier,

To reduce still more the thermal inertia of the filament, the filament 4 may be given the shape of a platinum tube about 2p. in thickness, which is covered with oxides, if required.

Fig. 2 shows practically the same receiving device as Fig. 1. Like reference numerals represent like circuit elements. Only the cathode 10 has been varied. The preferably thin-walled emissive sleeve is initially heated by a heater being situated within the sleeve. The wires of the heater are running in opposite directions and led out atthe centre of the emissive sleeve. In Fig. 3 an arrangement is shown in its principle, adapted in particular to receive very short waves. To avoid losses at the seals of the dipole through the wall of the vessel and to be able to make the radiation collecting part without the vessel of sufiicient length, the whole arrangement comprising the radiation collector and the cathode, has been made equal to an odd number of half wave lengths, e. g. 3/2)., 5/2ll etc. The cathode II and the seals l2 and I3 are positioned each at one voltage node of the stationary waves built up on the total arrangement.

In the operation of the device of the invention, it will be appreciated that the extra filament heating provided by the waves collected by the antenna gives plate current in proportion to the amplitude of the extra heating current,- and hence Q.' in proportion to the amplitude of the received waves. This extra plate current, varying in accordance with the wave amplitude, constitutes a modulation frequency current through the headphones.

What is claimed is:-

1. A tube detector comprising a space discharge device, radiation collectors attached to the terminals of the cathode of said discharge device, an indicator coupled to the plate' circuit of said discharge device, the said radiation collectors together with said cathode being so arranged that the total length amounts to 3/2x and 'one voltage node each occurs at the seals through the wall of the device and at the centre of said cathode where A is the length of the collected wave.

2. A tube detector comprising a space discharge device, radiation collectors attached to the terminals or the cathode of saiddischarge device, an indicator coupled to the plate circuit of said discharge device, the said radiation collectors together with said cathode being so arranged that the total length is an odd multiple including unity of half the length of the collected wave.

3. A tube detector comprising a space discharge device, radiation collectors attached to the terminals of the cathode of said discharge device, an indicator coupled to the plate circuit of said discharge device, the said radiation collectors together with said cathode being so arranged that the total length is an odd multiple including unity of half the length of the collected wave, and a voltage node occurs at the center of said cathode.

WALTER KRIEBEL.

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