US2438475A - Multirange tuner for ultra high frequency transmitters - Google Patents

Description

March 23, 1948. J. M. DODDS ET AL MULTIRANGE TUNER FOR ULTRA HIGH FREQUENCY TRANSMITTERS Filed Dec. 29, 1943 0 JIVUQ/MOW vawlim WWW John M Dpflds, JoiznM Lyd low,

29 1 v 30 33%! 5'3 30 K5 Fig-z lv CD3 Patented Mar. 23, 1948 QFFICE MULTIRANGE TUNER FOR ULTRA HIGH FREQUENCY TRANSMITTERS John Mathieson Dodds, Timperley, and John Heywood Ludlow, Bowdon, England Application December 29, 1943, Serial No. 516,104 In Great Britain May 13, 1938 13 Claims. 1

This invention relates to radio transmitters of the kind in which provision is made for changing expeditiously the wavelength of transmission by the substitution of different tuning inductances the one for another. Such arrangements are mostly employed in transmitters operating on relatively short wavelengths such as in the range of from 13 to 70 metres which is used for beam working wherein owing to changes in conditions of propagation an alteration of wavelength is usually to be effected frequently in order to ensure reasonable continuity of service.

In general, the wave changing arrangements comprise a number of inductances or tuned cincuts mounted upon a rotating structure or turntable each inductance being provided with switch 1 contacts so that any one of the inductances or tuned circuits can be connected to the associated power valve or valves. Such arrangement permits the change to be made in a relatively short time. Since on beam stations a separate aerial array is used for each wavelength, a selector switch has also to be operated to connect the appropriate feeder lines to the transmitter. In the use of such a rapid wave changing arrangement, having rotated the turntable to substitute one inductance or tuned circuit for another, the operator then sets the various variable tuning condensers to predetermined positions or values and causes the power to be applied, a final adjustment of the tuning condensers being usually necessary.

In our application Ser. No. 516,103 for Radio transmitters, filed December 29, 1943, wave changing arrangements are described involving switch arms for selectively connecting a plurality of fixed inductances to terminals of push-pull valves. It will be appreciated that in spite of the dimensioning and arrangement set forth in that application, owing to the finite inductance of the switch arms and the displacement of the inductance coils laterally from the valves, the minimum possible wavelength at which the valves can efiiciently operate is not achieved. The present invention is based on the consideration that when it is desired to resonate the valves to the minimum wavelength which can be achieved without recourse to series condensers, a satisfactory performance can be obtained when the inductance comprises a short straight wide bar connected directly between the electrode terminals and electrically weld joined to the latter. The inductance loop then comprises the bar and the electrode terminals of the two valves, the electrodes themselves and the supports of the electrodes. Such loop can satisfactorily be used for feeding in or feeding out high frequency energy by magnetic or other coupling means.

Regarding the mention in the preceding paragraph of the use of a series condenser, in many circuits when high power is handled at relatively high voltages, the series condenser if used effectively must have the same order of capacity as that between the valve electrodes. It will be appreciated therefore that the use of such a series condenser becomes difficult, owing to the high voltage developed across it, particularly in an anode circuit. If the condenser is of the air dielectric type it is inherently of large size in order to withstand the voltage and this fact, coupled with its high inherent inductance, is considered to outweigh the advantage otherwise derived from the use of such condenser. On the other hand other types of condenser than air dielectric condensers are generally found to be unsatisfactory on the very short wavelengths in question.

The object of the present invention is a rapid wave changing arrangement which permits the minimum possible wavelength to be achieved. As hereinbefore indicated the free radial length of the switch blades set forth in said application Serial No. 516,103 cannot be made less than the clearance required between the pairs of contacts or jaws to which the respective inductances are attached and between such adjacent parts as are alive when the switch is in another position to that which it occupies when in position to connect the selected inductance to the electrodes.

The present invention provides an arrangement by which the presence of the switch does not substantially affect the minimum wavelength to which the valves can be resonated, at least in one position of the switch.

According to the present invention the improved inductance wave changing arrangements comprise the electrode terminal member of a valve which terminal member has a switch contact face, an inductance terminal member having a contact face preferably parallel with the face of the electrode terminal member and spaced apart only a sufficient distance safely to withstand the working voltage stresses between said faces, and a movable contact blade or bridge having two opposite contact faces adapted to engage between the aforesaid two contact faces. The fixed terminal member of the inductance has or is adapted to have secured to it an inductance which for the minimum possible wavelength is a straight wide bar, that is to say wide in the direction par- 7 ther t ml arla;ic-an decir se h l d rr allel with the axis of the inductance loop formed thereby. The electrode terminal member may have a plurality of contact faces or alternatively it may have an extended contact face. Adjacent said other contact face or another part of the extended contact face may be arranged a further fixed induetances terminal member, so that by moving said bridge frolnione position-to another or employing twdalternatively operable bridges, the value of the inductance may be varied, the secnd or the further inductances having for instance a semicircular loop, a complete turn. or

more than one complete turn. Preferably the arrangement set forth is duplicated,.that isto say there is a bridge or blade member on ie ach s ide o f the inductance, the arrangement being symmetrical with respect to the i-nductange extended V tances .of -.-difierent,yalue in. the arrangement abov set; forth. one; or .more..of ,.the= inductances maybe variable-andcomprise a pair 'of parallel bars withtwhich the bridge or blade members are adapted. to make contact ashereinbefore.

verse inductance bar. .or

t tedw i e a bridge :is: slidably. arran ed-between said parallel bars. so that the inductancevalue can: be changed as desiredf' .l v

I-he-.;inventron.above.set forthmay be combined with; the invention forming the subject of the above mentionedapplication Serial No. 516,103 filed of even dateherewithby :using the aforesaid bridges or arms in conjunction with theswitch jaws or the equivalent to which apluralityof fixed inductancf'es; "are.-attached '.'in the, manner .described in:that.lapplication,the arrangement being such that the straight inductance bar-,(or

adjustablebridge) can b.e1-used when desired for V operation o n the wavelength. [The blade maybe wide in the axial direction throughout its length although its-width l is-actually. only required: e cb a h -t e' f q it t e clearances as hereinb ore mentiqnecl in the minimum ave c iti ne 7. 1-131. 7

eefi ren i eie r. cgm ris ei Q W E bsidiary f eature When-{applied more par- 1 tweenth ane iem nel a high power va nd terminal ohthe other electrodes is that the anode terminal'usually hasconsiderably greater. axial length, at least irr-thecase of fluid cooled yalves-ofthe-metal envelopetype; It will thus-be tappreciatedithatrastraight bar type of inductance maybe connected directly between the anodes ;of a pair-oi valves at any level within th engths of ,the anodes w'I-fhe positionloff the bar-forminimumwavelength would beat .the end of the anodes nearest to the terminalsoi the electrodes'with whichthe anodes are being resonated. A particular advantage in this connection arises from the fact that; the'lengtlreif thess witch bar or bladeis of the same gorder as that or the axial. length ofthe anode. Therefore according to this feature of the invention the hinge of the bridge or bladerma y'fbearrangedat thatilen'd of the. we. recesses-9c ages-recener The valves are preferably minimum wavelength as just above mentioned. Thus the switch blade may in one position be closed along the length of the anode so that in this position it makes contact with a contact race 5 of the anode in a position remote from the hinge, Y

whilst simultaneously in this position making contactiwitlrvarr inductance terminal, to which may be -con'nected the straight bar, other positions of the blade other inductances may be connected to the electrodes. To enable the invention to be clearly under- :stoodcertain; considerations leading thereto and certain arrangements thereof by way of example will now be described With reference to the ac-, companying-drawings in which:

Figure l is a simplified diagram illustrating the fundamentakprinciple of the present invention. Figure 2 isa similar diagram showing one embodiment of the present invention.

Figures 3 and 4 are front and 'side elevations of. aimore. practical form, of. the invention, and j, Figure 5,,fis ,a plan yiew, ,of a "modification Qof the V Eiguresfi and 7. areanelevationjand. plan r'epectiye bf. a1further-modificat o f t e nvention;

Refin .rst top f g. 1 .o ,.t e a' zq0mpah n drawings it is to be assumed that, as. hereinbeforeset forth two, similar valves injiaccordance WithJBritish Letters Patent Nm 41. .4753 arelope erated.inpush,-pull and the .anode circuit is res,- o'nated to the ,eflfictively earthed screening grids. Fiesland 2.. which. urely i g amma ic and 1O Z --W .j ii i$. det ls a em t. ro e;c ea the basic. ir nit 'ny tcdm a c rdanca-wi h. hein resent nve, 1011- .11 9 synol r present the amdes an th s r win gridsof a pair of. valves operated inpush-pull. ach a odeisslm orted n anxi n u atin qnv qp 'p .3 nd th te m nal 4 of ea h ,SPIQQQ; inggrid'. is led outannularly and. istefiectively onne te o. a .asthe high e nc qurreets a a on rne eart1. .l .a .reprc en ed'ai E h an a ecess t a cqns dcrable externallength, it being assumed that theane dei ygt k pplai a ns itu e a pore 1iJQ9 l F fi e-' v. inductance mophus formed will-Wary with-the pos iiwi the s ams-J al n ma et- The nearer 'is"th" ap -'nam'ely*=as india d a't 1, tofihe screenf g--gri d terminalfig'the smaller Y R ferring. 159% 9 37 .t el .t e.. eenunvens n. the avesm y; b qau ed. .i'o llaia'atili W et ime r g se s: a

' cncisg h a delis ol taqtff D 1 d etaifi if spi er-wai contact. faces: t2 and the gapbetween each face l and IE2 is made a minimum butv always suflicient to withstand: the'working voltage stresses between said faces. The gap t3 between said faces is adapted; to. have inserted in it a movable contact bridge which is not shown in Fig. 2. When said bridge is thusv in position the valves will clearly operate. at the. minimum possible wavelength. When said contact bridge is removed the inductance. H is no longer in circuit and. the anodes can be connected to another inductance. and; to this end the movable bridge may be; in the form of a pivoted or otherwise movable switch arm.

In aparticular arrangement illustrated by Figs. 3 and 4 each anode I oritsv preferably integral terminal has: pivoted to it at I4 the movable blade or bridge l5; the. pivot M being at that end of the anode which is remote from the: screening grid terminal (not. shown in Figs. 3 and 4). Thus when the pivoted switch contact blades or bridges [5 are in the positions shown in Figs. 3 and 4 the inductance strap or bar H is connected directly between the lower ends of the anodes. The member H is preferably wide in the direction which is parallel, with the axis of the inductance loop of which said member H forms a part.

By simultaneously swinging. the. two movable bridge members. away from their illustrated positions said movable :bridge members may be caused to engage any one of the pairs of jaw or other contacts l6, I? and I3 (Fig. 4) which are mounted on pillars or on a panel 59 and are connected respectively to inductance coils 28, 2! and 22. The member is shown in. dotted lines at l5a as connecting the inductance coil 2! through the inductance terminal contacts H to the anodesof the two valves.

At the lower part of Fig. 4 is shown a corresponding wave changing arrangement for the grid circuit, the member [5 in this case being pivoted to the grid terminal 23. For the minimum wavelength the member 15 engages jaws 24' which are connected to the straight inductance strap H which extends vertically downwards from the plane of the paper to the other valve, and each jaw is connected to the associated grid terminals for example by the longitudinal member 25.

If the valves are required to operate on a wavelength slightly higher than the minimum wavelength provided by the straight strap II at the lower ends of the anodes, the contact terminal members 12 maybe extended, as shown in Fig. 5, in the form of parallel bars 26 longitudinally between which is arranged to slide a bar 21, the position of which may be adjusted as will be fully understood, for varying the Wavelength more or less above the minimum, when the bridging members such as l5 are between the faces l0 and [2.

Referring lastly to Figs. 6 and 7 which represent a modification of the arrangement shown in Fig. 5, the terminals 28 of a pair of push-pull valves, for instance grid terminals thereof, may have secured to them annular members 29 carrying longitudinal contact faces 39 between which are arranged the straight bar inductance 3i and the inductance 32 having a semi-circular or larger loop. These inductances have contact terminal members 33, 34 so that the bridge [5 may be moved along the contact faces 30 to engage either the inductance terminal member 34 or the inductance terminal member 33 whereby to vary the inductance value to a relatively small extent.

Instead of all the engaging contact faces. such as H1, 12 being plane, certain of them may have straight or arcuate knife edges so as to: obtain a more efficient high frequency contact in the manner described with respect. to. Fig; 8' of said Application Serial No. 516,103 filed of even date; herewith, this particular feature being: a subsidiary feature of the present invention, but be:- ing more particularly claimed in the application lust above mentioned.

Reverting to Fig. 3 of the accompanying drawings the parallel lines 35 indicate. feedersby which the oscillations from the two valves; may be taken away, for instance to a di-pole aerial (not shown). It. will beunderstood; however, that inductive or capacity couplings: may be employed alternatively to the conductive coupling illustrated in Fig. 3.

We claim:

1. A short wave radio transmitterhaving wave changing arrangements and including a valve having an electrode terminal member; said member having a switch contact face, an inductance including a terminal member having a contact face spaced from said first face only a. sufiicient distance to withstand the working voltage between said faces, and a' movable contact having opposed faces adapted to be brought into; and: outof engagement with the-two first menti'oned contact faces.

2. A short wave radiotransmitter having wave changing arrangements: and of the character-de finedv in claim 1, wherein. one of. eacli pair of opposeidi contact faces is provided. with aknifeedgei.

3.. A. radio. transmitter of the: character defined; in claim 1, wherein the arrangements: are (1111311;- cated symmetrically for apai'r of pushepullavalves. and; with the inductance between; them and; including two contact: faces, one. opposite: the: con:- tact face of each valve electrodea terminal;

4. A short wave radio: transmitter having: wane. changing arrangements and. including a. valves having an electrode terminal member,v said mem ber having an elongated switch: contact. face, a plurality of inductanceseach including a contact face, each of said inductance contact faces being opposite a different longitudinal portion of said elongated contact face and being spaced from the latter only a sufiicient distance to withstand the working voltage between said faces, and a movable contact having opposite faces adapted to be brought into and out of engagement with opposed contact faces.

5. A short wave radio transmitter having wave changing arrangements and of the character defined in claim 4, wherein one of each pair of opposed contact faces is provided with a knife edge.

6. A radio transmitter of the character defined in claim 4, wherein the arrangements are duplicated symmetrically for a pair of push-pull valves and with the inductance between them and including two contact faces, one opposite the elongated contact face of each valve electrode terminal.

7. A short wave radio transmitter having wave changing arrangements and including a valve having an electrode terminal member, said member having a plurality of spaced contact faces, a plurality of inductances each including a contact face, each of said inductance contact faces being opposite one of said first-mentioned contact faces and being spaced from the latter only a sufiicient distance to withstand the working voltage between said faces, and a movable contact having opposite faces adapted to be brought into and out of engagement with opposed con- 7 tact faces. 7 V V 8. A short wave radio transmitter havingwave changing arrangements and of the character de- 9. A radio transmitter of the character defined in claim 7, wherein the arrangementsare duplicated symmetrically for a vpairrof push-pull valves and with theinductance between them and having two contact faces, one opposite a contact face of each valve electrode terminal.

10. A short wave radio, transmitter having wave changing arrangements and including. a pair of valves each having an electrode terminal member, each of said members being provided with a switch contact face, which two faces are opposed, an inductance betweenisaid faces comprising a pair of spaced conductors and abar slidable upon and between said conductors, each of said conductors including a face to oppose a valve terminal member face, a movable contact including two bars, each of, said bars including opposed faces adapted to be brought into contact with the face on one of said conductors and the opposed face of avalve electrode terminal. 11. A short wave radio transmitter of the character defined in claim 10, wherein said movable contact is'pivoted and other inductancesare positioned in its path of movement.

12. A short wave radio transmitter having Wave changing arrangements and including a valve having an elongated electrode terminal member, said member having a switchcontact face, an inductance including a terminal member having a contact face spaced from said other face only a sufilcient'distance to withstand the working voltage between said faces, a wave changing contact element pivoted upon said electrode terminal at a point remote from the position for minimum wave length, said contact element having a length substantially corresponding to the length of the contact face of said electrode terminal member, and a straight bar inductance, including a 'contact'face positioned to be engaged by said contact element when .the latter is in the minimum wave length position.

13. A short wave radio transmitter having wave changing arrangements and includingpa valve having an elongated electrode terminal member, said member having'a switchco'ntact face, an inductance including a terminal member having a contact face spaced from said other face only a sufficient distance to withstand the working voltage between said faces; a wave changing contact element pivoted upon said electrode terminal at a point remote from'theposition for minimum wavelength, said contact element having a length substantially corresponding to the length of the contact face of said electrode terminal member, a straight bar inductance including a contact face positioned to be engaged by said contact element when the latter is in the minimum wave length position,

and a plurality of inductances each including a contact face adapted to be selectively engaged by said contact element in other positions of the latter to thereby change the wavelength. 7

JOHN MATHIESON DODDS. JOHN HEYWOOD LUDLQW.

REFERENCES CITED The following references are of record in the} file of this patent:

UNITED STATES PATENTS Guy Mar. 31, 1942

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