US2218309A - Thermionic valve apparatus for use on very short wave lengths - Google Patents

Description

Oct. 15, 1949.

N. E. DAViS ET AL THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVE LENGTHS 3 Sheets-Sheet 1 Filed Feb. 2'7, 1955 INVENTORS NORMAN a. DAVIS ERNEST GREEN BY ALFRED w. HALL ATTORNEY.

Oct. 15, 1940. N. E. DAViS ET AL THERMIONIC VALVE APPARATUS FO R USE ON VERY SHORT WAVE LENGTHS s Sheets-Sheet 2 Filed Feb. 27, 1935 INVENTORS NORMAN E. DAVIS ERNEST GREEN ALF o w. HALL mrw l/ ATTORNEY Oct. 15, 1940. N. E. DAVIS El AL 2,218,309

THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVE LENGTHS Filed Feb. 27, 1935 Sheets-Sheet 3 INVENTORS. NORMAN E. DAVIS ERNEST GREEN BY ALFRy. HALL ATTORNEY.

Patented Oct. 15, 1940 UNITED STTES THERMIONIC APPARATUS FOR USE ON VERY SHORT WAVE LENGTHS Norman Eustace Davis, Ernest Green, and Alfred Weedon Hall, Chelmsford, England, assignors to Radio Corporation of America, a corporation of Delaware Application February 27,1935, Serial No. 8,470 In Great Britain March 10, 1934 7 Claims.

This invention relates to thermionic valve apparatus for use on very short wave lengths and more specifically to thermionic valve arrangements suitable for use in radio circuits adapted to operate upon wave lengths of the order of ten meters or less.

The invention may be utilized to provide an improved very high frequency amplifier and there will later be described in this specification a preferred form of very high frequency amplifier which can be satisfactorily employed on a wave length of about six to eight meters.

As is well known, satisfactory and efiicient thermionic amplifiers, for use on very short wave lengths of the order in question and for operation at high power, are dificult to construct. The requirements of such a high power very short wave amplifier may be generalized as follows:

(a) The circuit must be electrically symmetrical.

(b) There shall be electrical symmetry relative to earth. a

(c) Stray and uncontrollable capacitative and electromagnetic couplingsshall be avoided. (d) Interconnecting leads shall be as short as possible and as few as possible.'

(e) The whole'assembly shall be compact and rigid.

The present invention provides a thermionic valve apparatus in which the above requirements are satisfied to a very high degree, said apparatus being moreover comparatively cheap and easy to construct.

As will be seen more clearly later, the principal features of the invention reside in (1) the arrangement of symmetrically connected thermionic valves in containing screens or housings which also serve as electrodes in anode tuning and neutralizing condensers; (2) the provision of input and output circuits each symmetrically formed and each constructed as an easily re-- movable unit so that it may be adjusted when away from the other apparatus; (3) the provision of variable input and output couplings which 5 may be varied by moving the input and output circuits as units without at all upsetting the symmetry and electrical constants of the whole arrangement; (4) the utilization as part of the output inductance of an arrangement of metal tubes which are also employed to carry cooling water to the valves and the provision in association with-said metal tubes of tuning means whereby the output inductance may be varied without interfering with the water connections and with a minimum of alteration to subsidiary apparatus; (5) the utilization as part of the output inductance of the arrangement of tubes which also serve to conduct cooling water to and from the valves, and the construction of said tubesin such "manner that'they present a desired, relatively high resistance and thereby give the whole amplifier a, desired wide, band-pass characteristic. This last feature is one which is only required in cases where the amplifier is intendedto amplify a carrier wave modulated with 10 a wide band of frequencies, e. g., a television modulated carrier wave, and in cases where the wide band pass characteristic isnot required,

the tubes would be constructed to be of low high-frequency resistance. I 1.3

The invention is illustrated .in'the accompanying drawings'which' relate to a pre'ferred form of high frequency amplifier suitable for use on a wave length of the order of from 6 to 8 meters.

In the drawings: 20 Fig. lisacircuit diagram; Fig. 2 is aside elevation showing the amplifier general arrangement as seen through the side wall of its container cubicle;

Fig. 3 is a front'elevation of the'arrangement 5 shown in Fig. 2, the parts being again shown dotted since they are behind the front panel of the cubicle;

Fig. 4 is a plan view of Fig. 2 rotated showing the principal parts of the apparatus on 30 the output side of the screen V;

Fig. 5 'is a sectional elevation on a reduced scale through the line Q, Q of. Fig. 4, again showing only the principal parts; and

Fig. 6 is an end view of the apparatus shown. 35 in Fig. 5. Like references have been used for like parts throughout the figures.

Referring to 'Fig. 1, tnehigh frequency input, I e. g., modulated high frequency, is fed through adjustable condensers 2%, 25 to a coil 280. which 40 is variably coupled to a coil 18 tuned bya shunt condenser l9. Opposite ends of the tuned circuit l8, it are connected throughfcondensers l5, id as shown, to the grids of two symmetrically arranged valves or electronictubes l and 2 which 4 are of the known single ended typehaving watercooied anodes IA and 2A which form parts of the envelopes. The vaives are cross neutralized by condensers 8X connected between theanode of each valve and the grid of the other. The anode are. connected together through an inductance 9a and b, which is shunted by a .variable tuning condenser arrangement 5YY and the- inductance 9a and 9b is variablycoupled to a coil i la whose ends are connected through adjustable condensers 55 mounted, with its anode lo or 2a downwards, in

a triangular metal chair 3 or 4, each chair having. two vertical walls X and Y which are arranged so as to substantially shield the supporting insulators W (see particularly Fig. 6).. The walls X of the chairs are inclined towards one another and extend well beyond the walls Y, asshown in Fig. 4. The walls X are in electrostatic relationship with conductive plates 8.,(seeFig. 1)

which, with the said walls X constitute the cross connected neutralizing condensers 8X of, Fig.1. The chairs as a whole are, of course; in direct electrical L contact; with the; anodei jacketsyof the valves which are of course, at'anode potential.

Theplates 8-. are, movable, beinghingedupon hinges clearly shown in;Figj. 4 and, as will be at once apparent, are conveniently arrangedfor accurate adjustment and. neutralization: The plates 8' are cross, connectedto' the grids of the valve throughv conductors L3 and ltrespectively; thus the conductor, 43 connects oneof the plates 8 through a condenser I6 tothe-gridof the valve at l in Fig. 4, while the;other plate 8 is connectedthrough conductor"I4.- and condenser [E to the grid; ofthe valve at 2. The; grid leads from the condensers 15,15 are shown broken ofi in Fig. 4, but they continue in a direction to bisect the angles at -the corners ofthetriangular chairs, The ends of the conductors I'3 and l4 remote from the platesufi, are also.electrically and mechanically unitedwith conductors- Ila which pass through apertures in a screen-wall V and are formed at their end-5,815; Clamps or sockets for rectivin or. clamping plugs :formed on or ryin the rid tunin coil l-8;'; s ;is l rl shown in Fig. 3. It will. beg seenthat: this constructionresults in .avery. rigid'assemblyhwith very short cross, ancb interconnecting leads .and

good; shielding of. thejinput, circuit. The coil I8 is tuned by acondenser l 9 (see Fig. 3);;theplates of which; are .ca-rried'gupon; stems mountedupon the same iIiSlllHzlEOlSgthfit. help tocarry. the 'structures l1, Ila, l3, l,4-,'l'5 -,and.l.6.- .Fur,-thermore; as

will. appearmore clearly later, the inductance is is; at right. :anglesfltogthe inductance. in; the output circuit; The; anodes, ofv the valves are cooled by waterledthereto;throughpipes 9a, 9b

' which also; constitute the; anode. inductances.

- ment will behest seen from Figs. 4, 5 and 6.

These pipes are in parallel, and their'arrange- Water connections are made to these pipes via pipes in, la and anode potential is applied via the points at which pipes Iii, lfiajoinpipes 9a and 9b respectively. The anode inductance is tuned bythe condenser constituted by the arrangement shown at 5 in electrostatic cooperation with the plates Y of the triangular chairs. The arrangement at-5 consists of a hollow open ended copper box formed of two halves which may be adjusted with regard to their respective distances from the plates Y (see Fig. 4), the whole box being mounted as shown in Fig. 5, so that it may be slid longitudinally with respect to the chairs. Th-eguide plates along which sliding motion occurs are shown at B; and I is an attachment for a suitablemechanical drive. In effect, the box 5. iorms a ,plate'. whose distance 'of' a coil Ha which is positioned between and coupled to coils formed in the pipes 9a, 9b, the

. ends of the coil I la being connected each to one terminal'of; an adjustable condenser llb or No,

the remaining terminal of one of the two condensers H2), H being directly earthed to frame and the remaining terminal of the other of these two condensers being connected to a tubular output feeder shown at cl (Fig. 4). The whole unit Ha, Hb, He may, as will be obvious from Figs.

.4 and 5, easily be withdrawn and when withdrawn after detaching pipes Illa, adjusted and balanced-accurately. When the unit-isin position inthe apparatus,-. the couplingbetween. Ila. and-the inductances: constituted by the circular bends in thepipes 9a. and 9b may, be variedwithout at all disturbing the, symmetry or, electrical contents of the arrangement, by sliding thewhole output unit consisting ofthe parts Ha, II b, Hc along guides shown .at l2, [2a in-Fig..4.- I The inputcircuit whichis very similar is againmade up of; a} unit consistingofacoil 20a, condensers 2011 and. 200, and, as before,v the: coupling/can. be varied by vertically sliding the whole. unit 20a, 20b, 200 along guides 24 (seeFig. 3) this adjustment being. again. one that can be made. without disturbing the symmetry ,or. electrical constants.

The inputfeeder is, shown. at. 22in. Fig. 2. In Figs. 2 and 3, 23 representsftheglass. portions of the envelopes of the. valves; whose. anode. jackets are in the chairs-3 and 4 (the grid :lead-passing out through one of these glass portions to the condenser I6 is clearly shown in- Fig. 2.) 1 and 24 and 25 are filament bus bars.

. It will be noticed that, the-extensions of the walls ,X of the chairsbeyond. the triangular apices assists in electrically isolating the arms I3; and M of the bridge circuit. Thewalls X.-Y substantially shield the insulators w and thus minimize dielectric losses by advantageously distributing; the high frequency fields. Further, the maintuning control,;whichv islthe device for liding;;the:- copper box. S-andWhich enables. the tuning; ofthe whole 'circuit. when on. power, is at earth potential while the condenser arrangement Y-Y is extremely rigid andshouldbe ofi highly constant capacity. Again, theinsulator supporting: this condenser is'in: the electrical center. of

- the anode-circuit, andt-herefor there wouldbe noj heating or dielectric; losses.at..this point... If: inany particular installationan. anode-2m.- ductance; whichis lower. t-han.that which can be obtained-from an arrangement as so 'fardescribed andillustrated is required thi s may be effected by dispensing with-the circular bends in-the tubes Bag and; 912; A. preferred-arrangement,. however, which; may be usedr-whether such circular bends are-present or not, and .which has the advantage of permitting; easy; adjustmentof inductance, is that; illustrated in. Fig. .4. (the corresponding parts; are,-- not shown in Fig, 5'. for.- the-sake-of clarity.) and consists: of..t woadditional. metal tubes U of appropriate. diameter, v surrounding thertubes 9a; and Sbg-theysaid-tubes U being connected through a'thirdtubular member T ofl the same. or.- substantially; thesame diameter. .The structure.- 'I UU. isslidably arrangedlongitudinally and by sliding this structure along the pipes, the

anode inductance may be accurately adjusted as required without interfering with thewater supply to the valves. It will be. appreciated that the provision of the member T, though convenient practically, is by no means essential, for in many cases the, required inductance .could be obtained by using tubes U of fixed length surrounding the tubes, 9a and 9b andrigidly connected thereto, there being no bridge piece.

Apparatus as illustrated in the accompanying Figs. 2 to 6 may, with slight modification, be very satisfactorily employed for the amplification' and transmission of a very high, frequency carrier wave, e. g., of six to eight meters, modulated with a very wide band of modulation frequencies, e.- g., for television purposes. For example, a very slight modification is required in order that the illustrated apparatus may be satisfactorily employed, not as a final output amplifier, but as an intermediate modulated amplifier having a very wide frequency band pass, as for television signals. The modification consists merely in so arranging matters that the anode inductance presents substantial resistance whereby the inductance/resistance ratio is made of the required value to give the required wide band pass.

A preferred method of obtaining the necssary resistance consists in spraying the copper tubes 9a, 9b with soft malleable annealed iron or other material having similar electrical properties. If this be done, the high frequency currents, which will pass by reason of skin effect mostly along the outsides of the conductors 9a, 91), will suffer considerable loss due to the high permeability of the iron surface, while at the same time the advantages of copper piping for carrying the water are still obtained. In broad principle, this method of obtaining loss to secure a desired inductance/resistance ratio consists in utilizing the water passing down the tubes 9a, 9b to dissipate the required proportion of energy; that is to say, the high frequency loss is induced by reason of the external soft iron coating, but the heat generated by that loss is quickly and efficiently dissipated by reason of heat conduction through the copper pipe to the water. It is found that it is possible to make the anode circuit loss one third of the total output by the method described, and thus to secure a wide band pass characteristic. The advantages of the method described will be at once apparent when said method is compared with the usual known method of obtaining a desired relatively low inductance/resistance ratio namely, the known method which consists in loading back a suitable resistance component from the load. dif the load were, as is: usually the case, a grid circuit and this known method were employed, then, since a relatively small amount of power is; required for full grid excitation, a non-inductive load would have to. be built around the grid circuit in order to take the additional load required to throw-back to the anode circuit the required resistance and loss. For frequencies of the order in question, the provision of such a load circuit will usually be most undesirable, and in fact the stray capacity of such a load circuit would be likely to prejudice the tuning of the grid circuit at the very high frequencies concerned.

Although, in the specifically described and illustrated embodiment of the invention, triodes are employed, the said invention is not limited to the use of this type of valve, and screen grid yvalvesgfor example, could be used with advantage. ,Verylittle alteration would be required --to adapt the illustrated arrangement to incorporate screen grid valves, and if such Valves were currentblocking condensers. Even if screen grid valves were employed for power amplifier work, it is probable that balancing condenser 8X would still be necessary, or at any rate desirable.

What is claimed is: 1. A vacuum tube amplifier systemhaving a 1 pair of mutuallycoupled input coils and a. pair of mutually coupled output coils, each pair of said input and output coils being arranged at right angles to each other pair, an input circuit comprising one of said input coils having a condenser in series with each side of said input coil and terminals on said input circuit, means for sliding said last mentioned input coil and condensers as a unit into operative relation with the other input coil for said vacuum tube amplifier, an output circuit consisting of one of said output coils having a condenser in series with each side of said output coil and. terminals on said output circuit, and means, for sliding said last mentioned coil and condensers as a unit into operative engagement with the other output coil for coupling with said vacuum tube amplifier.

2. Apparatus as claimed in the preceding claim, characterized by the fact that said Vacuum tube amplifier includes a pair of tubes connected in push-pull fashion.

3. In combination, two pairs of metallic coridenser plates mounted and arranged opposite each other, each plate of said pair being located at an acute angle with respect to each other, an electronic tube supported within each pair of said plates whereby the anode of said tube is connected to said plates and acts as part of the anode tuning condenser for said tube, and means cooperating with the other of said angularly arranged plates whereby said other plate serves as part of the neutralizing condenser for the grid of an oppositely arranged tube.

4. In combination, two pairs of triangular metallic condenser plates arranged opposite each other, an electron tube mounted within and having its anode connected to each pair of triangular plates, means including a plurality of adjustable plates interposed between each pair of triangular plates for tuning the anode circuit of said tubes, and means including two other adjustable plates in capacitive relation with each pair of triangular plates for neutralizing the inter-electrode capacity of an oppositely arranged tube.

5. Apparatus as claimed in the preceding claim, characterized by the fact that coils are constructed of hollow tubular material to permit the flow of a cooling fluid therethrough, said coils having their axes at right angles to each other and connected across the plates and grids of said tubes.

6. In combination, two pairs of triangular metallic condenser plates arranged opposite each other, an electron tube mounted within and having its anode connected to each pair of triangular plates, means including a plurality of adjustable plates interposed between each pair of triangular plates for tuning the anode circuit of said tubes, means including two other adjustable plates in capacitive relation with each pair of triangular plates for neutralizing the interelectrode capacity of an oppositely arranged tube, a hollow tubular conductor connected across the anodes of said tubes, and a, plurality of metallic sleeves mounted about portions of said hollow conductor for varying the inductance thereof.

7. An amplifier system comprising two electron amplifier tubes, a pair of mutually coupled inductance input coils and a pair of mutually coupled output coils, each pair of input and output coils being arranged at right angles to each other pair, an input circuit comprising one of said input coils having a condenser in series with each side of said input coil and terminals on said input circuit, means for sliding said last mentioned input coil and condenser as a unit into operative relation with the other input coil of said electron amplifier tube, two pairs of triangular metallic condenser plates arranged opposite each other, each one of said electron tubes mounted within and having its anode connected to each pair of triangular plates, means including a plurality of adjustable plates interposed between each triangular plate for tuning the anode circuit of said tubes, and means including two other adjustable plates in capacitive relationship with each pair of triangular plates for neutralizing the inter-electrode capacity of an oppositely arranged tube, an output circuit consisting of one of said output coils and having a condenser in series with each side of said output coil and terminals on said output circuit, and means for sliding said last mentioned coils and condensers as a unit into operative engagement with the other output coil for coupling with said amplifier.

NORMAN EUS'I'ACE DAVIS.

ERNEST GREEN. ALFRED WEEDON HALL.

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