US2031490A - High frequency circuit - Google Patents

Description

Feb. 18, 1936. F; A. KOLSTER ,499

HIGH FREQUENCY CIRCUIT Fild Oct. 51, 1954 Siam 2.9

frezZerz'aZA.fioZaier INVENTOR ATTR Y Patented Feb. 18, 1936 UNITED STATES PATENT OFFICE HIGH FREQUENCY CIRCUIT Application October 31, 1934, Serial No. 750,819

6 Claims.

This invention relates to high frequency circuits, and particularly to tank flywheel frequency determining circuits especially useful in connection with vacuum tubes employed as oscillation generators.

An object of the invention is the production of such a tank circuit, the frequency characteristic of which is substantially constant for wide variations in temperature of the elements 10 thereof.

Another object of the invention is the provision of such a tank circuit formed as a, simple, compact unit, easily mounted and adjustable over a fairly wide range of operating frequencies.

In one of its aspects the invention is an improvement over my co-pending application Ser. No. 637,564, filed October 12, 1932, and particularly as disclosed in Figures 1 to 3 thereof.

A tank circuit embodying the invention is particularly useful in high frequency radio systems employing frequencies of 60,000 kilocycles, that is, for wavelengths of five meters and below.

Other objects of the invention will appear from the description and claims.

An embodiment of the invention is illustrated in the accompanying drawing, wherein:

Figure 1 is a front elevation, partly in section, of the unitary tank circuit;

Figure 2 is a broken right end elevation of the device of Figure 1; and

Figure 3 is a top plan of the mechanism for adjusting the tank circuit.

The tank circuit according to the invention comprises a closed oscillatory circuit containing inductance and capacity elements. The principal inductance element is formed as a tube of high conductivity copper. This tube I is connected at each end by coupling rings 2 to extension tubular members or end tubes 3 and 3a, which are also of high conductivity copper. The

tubular member I with the end tubes and coupling rings are held together as a unit by means of supporting metallic blocks 9 and co-operating tie rod III which extends through said members '45 and is provided with nuts 29 which hold the assembly firmly together. The supporting blocks 9 are each provided with two openings So for the passage of bolts employed to fasten the structure to supporting insulator pillars 30.

Supported upon the left end tube 3a is a cupshaped member 3| having radially projecting flanges l3 which serve as condenser plates. The cup-shaped member 3| has a split tubular extension 32 surrounding the end tube 3a and provided with a pair of flanges 33 on opposite sides thereof, through which bolts extend for clamping the cup-shaped member 3| in proper position on theend tube 3.

A second cup-shaped member 35 is rotatably supported on the right end tube 3 by a tubular 5 extension 36 fitting over tube 3. This cup-shaped member 35 has radially extending flanges [4 similar to flanges l3 on the other cup-shaped member. These flanges I I are the same in number as the flanges i3 and serve as condenser plates. 10 Flanges l3 form condenser plates of the stator of the condenser, while flanges [4 form the condenser plates of the rotor of the condenser.

As shown, the rotor and stator condenser plates are staggered and there are eight of each. This 15 number may be increased or decreased, but with eight, the tuning angle of the condenser is about 15 degrees.

The rotor 35 of the tank circuit condenser may be rotated to vary the distance between the rotor 20 and stator plates by means of a worm drive. This worm drive comprises a worm gear 8 carried by a worm shaft I2 rotatably supported in a drive bracket l I, the worm 8 being fixed to shaft l2 and spaced from the arms of the bracket by means of spacing sleeves 8a. The bracket II is formed at its lower end so as to surround end tube 3 and is split so as to be held firmly in clamped adjusted position thereon. The worm 8 engages a worm gear segment 1 formed on an '30 annular plate 31 which surrounds the end tube 3 and is held in spaced relation thereto by being bolted or otherwise fastened to lugs 38 provided on the rotor 35.

For operating the worm 8 a hand-wheel 39 is 5 connected to the shaft [2, an elongated insulator 40 being interposed between the hand-wheel 39, which may be of metal, and the worm shaft l2. The tank circuit ordinarily will be mounted back of a panel, with the operating hand-wheel in 40 front thereof.

The condenser rotor 35 is held yieldingly in its extreme left position by means of a coil spring 4| surrounding end tube 3. This spring is interposed between the annular member 31 carried by the 45 rotor and a thrust ring 42 also surrounding the end tube 3 and positioned adjacent the bracket ll. One end of this spring is fixed to the rotor by being fastened under the head of the screw 22, while the other end is fastened to an extending lug 43 on the bracket II by being fastened under the head of the screw 23.

The spring also assists in holding the rotor in adjusted position, and prevents any backlash in 55 the operating mechanism from afiecting the adjusted position of the rotor.

The cup-shaped stator 3| and rotor 35 with the condenser plates may be cast of bronze, and then copper-plated. To prevent corrosion the stator and rotor may be lacquered.

It will be noted that the coupling rings 2 are formed at one end as plugs 45 inserted in the ends of the central tubular inductance :member '.I. The oppositeside of each of the rings 2is formed to receive end tubes 3 and 3a. Each coupling ring 2 is also formed with a conical surface "46 against which a like conical surface on the stator and the rotor is held in firm electrical contacting engagement. This electrical engagement between the mating conical surfaces on the stator 3| and the coupling ring 2 is maintained by the stator being held in clampedpositiomwhile such contact between the mating conical surfaces of the rotor and the other coupling ringmaintained due to the action .of the coil spring 4]., so that as .the rotor is adjusted the said contact is maintained.

The particular construction of employing a central tubular inductance landend tub,es 3 with coupling rings 2 permits the use of inductance tubes 1 of differentrdiameter,.southatthe operating frequency range of the circuit may .be altered. To make suchalteration it is merely necessary to provide central .tubes of other diameters and other coupling rings with the plug .ends thereof or" appropriate diameters. A tubular inductance element of .sufiicient length may be employed thereby eliminating the coupling rings and end tubes.

The stator and rotor are, of course, maintained with their open ,faces in spaced relation. For

making electrical connection to the electrical midpoint of the inductance element of the tank laircuit, the tubular inductance element .1 .is provided with a clamp 18 surrounding the .tube. This clamp 18 may be .heldin adjusted position by means of a set screw 4.1.

The length of the rotor and-stator condenser plates I3 and M is such that as the structure expands and contracts slightly under varying temperature conditions the area of Opposed plate surfaces will remain constant. Thus, the varying conditions of expansion and contraction will have no effect upon the capacity of .the tank circuit insofar as the plates of .the condenser element are concerned because the spacing and opposed area thereof remain constant. The expansion and contraction, under varying heat conditions, will, however, cause .some slight changes in capacity due .to the varying of the distance .between the opposite open ends of the stator and rotor. The capacity between the opposite edges of these cup-shaped members is very small and forms only a very small part of the capacity in the tank circuit. The variations in such capacity between the opposing edges of these cup-shaped members may be reduced still further-by reducing the thickness of the wall of thecup-shapedmembers at the 'opposing'edges, and/or by increasing the distance between them.

The inductance of a tank circuit is formed by the central tube l together with the cup-shaped members 3| and .35. The inductancepathof the tank circuit is, therefore, toroidal.

The resistance of the tank circuit is extremely .low, being of the order-.of less ithanone-hundredth of an ohm.

Tank circuits embodying invention :have been constructed in which :for wavelengths of three meters, the capacity micro-micro-farads, the inductance approximately .05 micro-henries, and the resistance approximately .009 ohms, which gives a Q of upwards of 3000, the value of Q being determined from the formula Q x/i- -v where L'isthe inductance, R the ohmic resistance, and C the capacity of the tank circuit. Such a tank circuit has been found to be very useful in connection with vacuum tubes for the production of high frequency oscillations.

In another practical embodiment of the invenit'iomt'he -tank circuit constructed was capable of use in oscillation generator systems in the produc- 31210151 :of wavelengths varying between three and five meters. By increasing the diameters of the central inductance tube I, the oscillations of shorter wavelengths are produced.

In tank circuitsembodying the invention, which have been constructed, the frequency stability has-been remarkably good. Thus, for temperature changes of 30 centigrade, there has been a change in frequency of :less than 2,000 cycles in 60,000,000.

Although the tank :cicrcuit has beenillustrated as being mounted with the inductan'cetube l in horizontal position, the mounting may be such as .to have the tube I extend vertically. When so mounted, insulating pillars 30 will not be required forthe cup-shaped stator 3| willrest-uponandbe fixed directly to supporting insulators.

What is claimed is:

1. An electrical circuit comprising a metallic tube 'forming an inductance element of said circuit, a pair of dome-shaped metallic devices mounted in spaced relation at opposite ends of said tube in electrical contact therewith, one device being fixed and the other rotatable relative .to said tube, flanges on both devices positioned to .form a variable capacity element of the said circuit and so that the separation there-- is approximately 60 \of is variable by rotation, and means for rotating said rotatable device to vary the distance between the flanges of said devices.

2. An electrical circuit comprising a metallic tube .iorming an inductance element of said circuit, a pair of dome-shaped metallic devices mounted in spaced relation at opposite ends of said tube in electrical contact therewith, one of said devices :being rotatable relative to the other, and radially extending flanges on both devices positioned to form a variable capacity element .of the said circuit and so that separation thereof is variable by rotation.

.3. .An electrical circuit comprising a metallic tube .-forming an inductance element of said circuit, a pair of dome-shaped metallic devices mounted in spaced relation on said tube in electrical contact therewith, one .of said devices being rotatable relative to the other, radially extending flanges on said devices positioned to .form a variable capacity element of said circuit and so that the separation thereof is variable by rotation, and means for rotating said rotatable device to vary the capacity between the said flanges.

4. An electrical device comprising, as a com- :posite' unit, a .conducting rod constituting an inductance element of an electrical circuit, a pair of spaced conducting members electrically connected to said rod, one :being rotatable relative to the other, said members forming a variable capacity element co-operating with said inductance element to provide a closed oscillatory circuit and being so positioned that the distance therebetween is variable by rotation, and means for rotating said rotatable member to vary the distance between said members.

5. An electrical circuit comprising, as a composite unit, a metallic tube forming an inductance element of said circuit, a pair of domeshaped metallic members mounted in spaced relation along said tube in electrical contact therewith and co-operating with said element to provide a toroidal inductance path, and a plurality of equally spaced radially extending flanges on each member, the flanges of one member being staggered with respect to the flanges of the other and positioned to present opposing faces thereby to form multiply connected capacity elements of said circuit.

6. An electrical circuit comprising, as a composite unit, a metallic tube forming an inductance element of said circuit, a pair of dome-shaped metallic members mounted in spaced relation along said tube and in electrical contact therewith whereby under varying operating temperatures said spacing varies due to expansion and contraction of said tube, and radially extending flanges on said members positioned in opposing relation to form a capacity element of said circuit the capacity of which is unaffected by variation in said spacing.

FREDERICK A. KOLSTER.

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