Патент USA US2407147код для вставки
Sept. 3, .1946. N. v. FEDQT‘QFFI I v2,407,147 ‘ADJUSTABLE TRANSMISSION LINE Filed Feb. 27, 1945 3 Sheets-Sheet 1 use, ll) ‘10 o“scl<Lur5on3 MET R DETCOR (s5 _ INVENTOR. \ NICHOLAS V. FEDOTOFF ATTORNEY Sept 3, 1946' I ‘ N. V._FEDOTOFF ‘ 2,407,147 ADJUSTABLE TRANSMISSION LINE _ Filed Feb._ 27, 1945 ' 3 Sheets-Sheet 2 I03, A43 '14 ‘ Q? 2% \ . ~= 8 ~\\ \ s 1"- ~§, ‘FA “\// g g Q \ \ \ > § > x _. INVENTOR. ’ ’ NICHOLAS v FEDOTOFF BY” E = \ /./; E c9 \ ' g ‘ ATTORNEY ' ' Sept. 3, 1946. ‘2,407,147 N. V. FEDOTOFF ADJUSTABLE TRANSMISSION LINE Filed Fe_b. 27, 1945 ~O 3 Sheets-Sheet 3 £13 5mm.. N9 “02 > INVENTOR. NICHOLAS. V. FEDOTOFF A‘E'TORNEY Patented Sept. 3, 1946 ‘ 2,407,147 ‘UNITED STATES PATENT OFFICE‘ 2,407,147 ADJUSTAB‘LE 'TRANSMIS SION LINE Nicholas V. Fedotoff, Lynbrook, N.‘_Y., assignor, by mesne assignments, to Hazeltine Research, Inc., Chicago, 111., a corporation of Illinois ' ‘ Application February 27, 1945, Serial No. 579,975 12 Claims. 1 2 This invention is directed to transmission lines ,of adjustable electrical length. While the inven tion is subject to a variety of applications, it is especially suited to short-circuited transmission‘ lines- and will be particularly described in that connection. Short-circuited transmission lines of the type _'under consideration comprise a pair of conduc tors usually arranged in either spaced parallel or ‘coaxial relationship to have uniformly distributed inductance and capacitance. The effective elec trical length of such a line may be adjusted by means of a short-circuiting element bridged i - struction, rotation of the inner conductor ad vances the tuning element along‘ the line for tuning. This construction‘ has the advantage that the physical dimensions of the structure do not vary with tuning. However, from a mechan ical standpoint it is desirable that the inner con ductor be made of steelbut steel is a poor con ' ductor at ultra-high frequencies, Furthermore, it is necessary to, lubricate the threaded portion of the inner conductor whereasbest operation of the line requires that its conductors be maintained clean. . Additionally, the discontinuities in the skin of the inner conductor resulting from the across and freely slidable along its conductors. screw thread may impair the conductive char Where the adjustmentof the short-circuiting ele 15 acteristics of the transmission line. ' ' ment is such that the electrical length of the line . ‘It is an object of the invention, therefore, to plus its terminating impedance‘ is equal to ‘one provide a transmission line of adjustable elec quarter of its op'erating‘wave length, or an in— tegral multiple thereof, the ‘line exhibits imped _ ance characteristics analogous to those of con ‘trical length which avoids one or more of the above-mentioned limitations of prior art arrange ments. ‘ , , ‘ ‘ - , ventional resonant circuits and is said ,to be a‘ resonant line. Since the frequency-response characteristic of a resonant line may be readily modi?ed through adjustment of its short-circuit ing or tuning element and in view' of other well trical length having reduced space requirements. tions, path by‘ the driving member, It is a further object of the invention to provide an improved transmission line of adjustable elec , A, transmission line of adjustable electrical length in accordanceiwith the invention com recognized properties of Jlinearrangements, res prises a first conductor and a second Iconductor, onant lines are widely used as frequency-selec the latter having an axially extending slot and a tive or frequency-determining circuits of Wave predetermined spaced relation to the ?rst con signal translating apparatus designed for oper "ductorh An ‘adjustable member is movable in a ation at ultra-high frequencies, 30 predetermined path in the. space between the ‘con In one short-circuited line arrangement of the ductors, for varying the electrical length of the prior art, the position of the tuning element is transmission line including these conductors. adjustable through a mechanical link disposed The arrangement also comprises a driving, mem along the line in the space between its conduc “ber disposed within the second conductor for ex ‘ tors and a?ixed to, the tuning element, the link ‘?Iting‘ a controllable driving force along the line. ' and tuning element together constituting atuning “ The‘, line also has means projecting through the , plunger axially movable along the line. While ‘slot of the second conductor into mechanical coupling engagement with the‘adjusta‘ble mem arrangements of this type have proved to be oper ber and the driving member‘ for effecting a ‘dis ative,‘ they have ‘certain inherent limitations placement ‘of the adjustable member along its which may be objectionable in particular installa For example, as ‘the tuning plunger is ‘ , For a better understanding of the present in length, the’ over-all ‘physical length of ‘the ar . vention, together with other and further objects rangement is increased progressively. Where , thereof, reference is had to the following descrip space limitations are important, this feature may 45 tion taken in connection with the accompanying withdrawn from the line to increase its electrical , be undesirable. ‘ ‘In another line ‘structure of the prior ‘art in which the conductors have a coaxial or concen , tric relationship, the inner conductor is rotatably supported ‘and is provided with a screw thread adapted to engage a threaded bushing of the tun ing element. Additionally, the tuning element is slidably mounted on one or more guide rods posi tioned in the interconductor space which lock the drawings, ‘and its scope will be pointed out in the I appended claims. In the drawings, Fig. 1 is a cross-sectional view, partially‘broken aw‘ay,of a transmission line con 50' structed ‘in accordance with theinvention; Figs. 2 and 3 are additional sectional views taken as indicated by section lines 2-2 and 3—3, respec tively, of Big. 1; ‘Fig. 4 is a schematic ‘represen tation of a wave meter arrangement utilizing the‘ tuning element against‘ rotation, ,With this ,con 55, transmission line ofFigs. .1-3,inclusive; Fig. 5 is 2,407,147 4 1 Fig. 9 is a schematic circuit diagram of a power lead screw 25, the line arrangement includes means projecting through the slots l1 and N3 of the inner conductor into mechanical-coupling engagement with both the adjustable short-cir cuiting member and the driving member 25. As i bridge network utilizing the transmission line of illustrated in Fig. 2, this means consists of a a cross-sectional view of a further embodiment of the invention; Figs. 6, 7 and 8 are additional sectional views taken as indicated by section lines 6—6, '|—l and 8--8, respectively, of Fig. 5; and threaded bushing 35 having diametrically op posed extensions 36 and 31. The threaded por tion of the bushing engages lead screw 25 while of the coaxial or concentric type. It comprises 1O the extensions 35 and 3'! thereof project, respec tively, through slots l1 and I8 of the inner con a hollow outer, or ?rst, conductor I0 and a hollow ductor tobe secured to the short-circuiting mem inner, or second, conductor II, each ofwhich is ber by way of machine screws 38. Also, extension circular in cross section. Thesecond conductor Figs. 5-8, inclusive; Referring'n'ow more particularly to Figs. 1', 2 and 3, the transmission line there represented is is coaxially disposed within the. ?rst conductor 36‘is su?icientlylong to extend through longitudi so as to have a predetermined spaced relation: ‘ nal. slot |~B of outer conductor ID to serve as an with reference thereto. A pair of centrally aper tured end plates I2 and H) of conductive material are ?tted to the opposite ends of conductor ID. A conductive bushing I4, inserted into the aper indicator for permitting the position of the short circuiting member to be determined upon inspec tion. A calibrated scale (not shown) is associ ated with slot I8 so that extension 36, in con junction therewith, provides a direct indication of the resonant wave length of‘the transmission line for each adjustment of its short-circuiting ture of end plate l2 and nonrotatably supported - -' thereby, is received by one end of conductor | | to establish the desired coaxial alignment of the in ner and outer conductors. The alternate end of conductor II is supported in a manner described hereinafter, to complete the desired coaxial align ment of these conductors. element. An additional threaded bushing 40, having the same general con?guration as bushing 35, is also included in the line arrangement. This addi tional bushing is slidable along a pair'of studs 4| and 42 extending from bushing 35. Each of the bushings is centrally recessed to house a helical One or more machine screws l5, locking conductor H to. bushing I4, hold the inner conductor against rotation. An axially extending‘or longitudinal slot I5 is milled into conductor I0 and similar but diametrically spaced slots l1 and- I8 are cut into conductor H. In assembling the line arrangement, its con ductors areso oriented that slots I6, I‘! and I8 are in vertical alignment. spring 43. The added bushing, in conjunction with spring 43, constitutes an anti-backlash mechanism. Energymay be supplied toy or taken from the transmission line by means of pickup devices which may be accommodated by suitable recep tacles 5E! and 5| projecting through conductor The transmission-line structure includes an adjustable membermovable in a predetermined path in the space between conductors I0 and II for varying the electrical length of the line con stituted by, or including, these conductors. For the illustrated arrangement, this adjustable 40 H! as clearly disclosed in Fig. 3. These recep tacles are preferably diametrically opposed and therefore the circuit arrangements coupled there to are shielded by the centrally located inner conductor ||. member short-circuits the inner and outer c'on The current-carrying elements of the line ductors to determine the electrical length of the line-and is provided by a ring 2!] having a series of resilient contact ?ngers 2| and 22 disposed about its inner and outer peripheries. Contact ?ngers 2| and 22 are suitably ‘formed and proportioned to engage the inner and'outer conductorsv of the line so that the short-circuiting member is sup ported by and freely movable along these con structure, suchas conductors l0 and H and con tact ?ngers 2| and 22 may be formed of brass and are, preferably, silverplated to have improved conductivity characteristics. Shaft 24, however, is preferably machined from steel stock. The illustrated embodiment of the invention effectively comprises a coaxialitransmission line which is short-circuited at each end and may, therefore, be considered as a resonant cavity. ductors in the space therebetween. A driving member is disposed within the second or inner conductor ll of the line for exerting a The effective electrical length of the cavity is equal to one-half its resonant wave length and controllable driving force therealong and for aid ing in establishing the‘ coaxial alignment of the may be adjusted by displacing the short-circuit inner and outer conductors. This driving mem-~ 56' ing member along its inner and outer conductors to tune the cavity over a predetermined range ber is provided by a rotatable shaft 24 a portion of operating wave lengths. In this connection of which is threaded, as indicated at 25, to form it will be apparent that the wave-length range a lead screw. One end of shaft 24 is rotatably is determined by the permissible range of dis supported in a bearing26 secured to a centrally located recess in the end of bushing l4 which is‘ SO placements of the short-circuiting member. Therefore, the physical lengths of conductors l0 adjacent this end of shaft 24. Preferably, bush and II, which are shown inde?nitely in Fig. l, ing 26 is constructed of an oil-impregnated ma are selected with a view to obtaining a desired terial to be self-lubricating. The opposite end range of operating wave lengths. ' of the shaft is rotatably, supported in a bearing The schematic circuit‘ diagram of Fig. 4 repre 2'! retained in endplate l3 by means of retain (35 ing rings 23 and 29. This shaft also projects sents the application of the described line ar rangement to a wave‘ meter system for determin through a bushing construction 30 carried by the free end of conductor | l- and serves to maintain ing the operating wave length of an oscillation generator 53. ' the coaxial alignment of conductors I0 and H. The'free end of shaft 24 extends beyond end plate‘ I3’ and supports a crank 3| through which the rotation of the lead screw may be controlled. In order that the adjustable short-circuiting member 20, 2|, 22 may be selectively displaced along'thev transmission line under the. control of ‘ A coupling loop 52, coupled to generator 53 and extending into the resonant cavity by way of one of its receptacles 50 or 5|, excites'the cavity. A second coupling loop 54 ex tending into the resonant cavity through the other of its receptacles couples a detector 55 The output circuit of the detector is thereto. 2,407,147 5 , coupled to a meter 55, such a'sa voltmeter- In operating the wave meter system‘, lead screw 25 6 . ~ The effective electrical length‘of the transmis ductor II lock bushing 35 against rotation so that this bushing and the short-circuitingmem sion line, including conductors<l03 and I06, may be adjusted by, means of a ‘conductive short-cir cuiting member or yoke I30 which is supported by and freely movable along the line conductors. ber carried thereby are displaced along conduc As illustrated in Fig. "7, the'short-‘circuiting yoke tors I0 and II by lead screw' 25. This'adjust ment of the short-circuiting member varies the electrical length of the resonant cavity, tuning I30 is essentially a circular disc apertured to-ac commodate conductors I03 and I06 and having resilient contact ?ngers I31 and I32 which en is rotated by crank 3|. The slots of inner con the cavity over its range of operating wave gage the line conductors andafford a desired connection to the yoke. An indicator I33, se cured to the upper section of yoke I30 and project ing through slot II 3 of the shield, enables the position of the short-circuiting member to be ?ection is obtained on meter 50. The operating wavelength of oscillator 53 may then be deter 15 determined upon inspection. If desired,‘ the shield may be suitably calibrated to indicate the mined from the position of ‘ projection 36 with operating wave length for particular settings of reference to the wave length scale associated with lengths. When the effective electrical length of the cavity corresponds to one-half the operat ing Wave length'of the oscillator, a maximum de slot IS in conductor I0. . member I30. > As in the described Fig. 1 embodiment, the driv of the present invention to a transmission line 20 ing member for effecting displacements of, the short-circuiting yoke I30 along the line is pro including a pair of spaced parallel conductors as Figs. 5-8, inclusive, illustrate the application vided by one or‘ more lead screwsvrotatably dis sociated with a bolometer element to be utilized posed within the line conductors. Preferably, two as a component of a ‘power-measuring bridge such lead screws are provided, one- being indi~ _ network. The line arrangement is enclosed with in a conductive shield I00 having a circular cross 25 cated at I 40 and disposed within conductor‘ I03 while the other‘ I“ is located within conductor ‘section and conductive end plates I BI and I02. I05. One end of each lead screw has a reduced The transmission line includes a ?rst hollow con cross section and projects through end plate I02 ductor ‘I03 having a longitudinal slot I04 and of the shield to support driving gears I42 and carrying at one end a conductive bushing I05 for I43. A third gear I44, meshing with gears I42 effectively'extending the conductor. A second and I43 and supported by a. stub shaft I45, pro conductor has a similar construction‘ and consists vides a unicontrol for e?ecting identical adjust of a hollow conductivemember I06 with a longi ments of lead screws I40 and MI. Stub shaft tudinal slot I01 and a conductive bushing I08. I45 is also rotatably supported within end plate These conductors are assembled in ‘spaced par I02 and carries upon itsfree end a crank I46 allel-“relationship, being‘secured atone end to for controlling the driving members I40 ‘and ‘suitable recesses in end plate I02 of the shield and being supported at their‘ opposite ends by a As illustrated in Fig. 7, yoke I30 is slotted to disc I09 of insulating material and apertured to receive a pair of threaded'vanes I 50 and‘ I5I receive conductive bushings I05 and I08. Disc I09, in turn, is mounted by means of brackets .40 which engage lead screws I40 and MI, respec tively, for effecting displacements of the yoke H0 and III to a conductive collar II2 slidable member by the lead screws. Vanes I50 and I5I along shield‘ member I00. In order that collar MI. I r . I. > I I2 may‘slide along the shield, the shield is ‘slotted ' are locked in position by means of threaded pins as indicated at I I3 and I I4, the slotshaving su?i cient width‘to accommodate brackets H0 and I I I. A series of tabs I2I are struck out of collar IIZ, as shown in Fig. 8, and‘ are depressed fric tures in the yoke I30 and each of the vanes. Fig. 9 represents a schematic circuit diagram of tionally to engage shield‘ I00. ‘ A bolometer element II5, consisting of a cen I52 and I53 which project through aligned aper a bolometer-type power-measuring bridge net~ work, utilizing the line arrangement of Figs. 5-8, inclusive, for measuring the power output of an ter-tapped temperature-variable resistor en- : ' closed within a glass envelope, is supported upon oscillation generator I55. The bridge network is similar to the well-known Wheatstone bridge in disc I09 by means of insulating, straps HE. A conductor I24 connects with the center tap of the bolometer and is drawn through an opening of shield‘ I00 to connect the bolometer element into a bridgevnetwork. This element is also elec that it essentially comprises a network of re sistors. Three of the arms or the bridge are pro vided by a variable resistor IBI for balancing the trically coupled to conductors I03 and I08 by wayof connectors Ill and H8, extending from the opposite ends‘of the bolometer element to re silient contact ?ngers H9 and I20. Thesecon tact ?ngers are secured to disc I09 and are suit ably shaped to engage bushings I05 and I08 of the transmission-line conductors I03 and I05, re spectively. The ‘adjustable mounting of disc I09 is provided to permit adjustment of the coupling bridgenetwork in the face of ambient tempera _ ture variations, a variable resistor arrangement I62~calibrated with reference to bolometer ele ment I I5 to read directly in terms of power and ' a'?xed resistor I03. The remaining arm of the bridge includes the line arrangement of conduc tors I03 and I00 and their associated bolometer , element II5. ‘ The line arrangement; is:coupled into the bridge circuit by means of the conductor _ I24 extending from the mid-point of thebolome ,ter element H5 and a second conductor I50 coupled to the shield I00. A source I64 of unidi rectional potential is coupled to one pair of di for a purpose. to be made clear hereinafter; A pickup loop'l25 is received by apertures in com agonal terminals of the bridge and an ammeter I85 is connected between the remaining diagonal ductive bushings I05 and I08 and serves to cou— ple the transmission line to a circuit arrange- " terminals; The bridge network is positioned ad jacent oscillation generator I55 with its pickup ment, such as an oscillation generator, for the loop I25 inductively coupled thereto,‘ as ‘by? way purpose of making power measurements; This loop projects through an opening I26 of end-plate of an inductor I55. While radio-frequency en IOI and may be adjustedlongitudinally of the ergy is applied to the bolometer element I I5 from .line, by means of set screws. I21 and‘l28; transmission line conductors I03 and I00, ‘only of the bolometer. element to the line conductors, '2,407, 147 8 direct current‘ is applied to'the bridge arrange ment in view of the connection I24 to the mid What is claimed is: l. A transmission line of adjustable electrical length comprising, a ?rst conductor, a second conductor having an axially extending slot and point. of the bolometer and conductor I60 to the shield. a predetermined spaced relation to said ?rst con In making power measurements, the bridge ductor, an adjustable member movable in a pre network is initially balanced by adjustment of determined path in the space between said con resistor IGI but with the bridge decoupled from ductors for varying the electrical length of the the oscillation generator. Having established the transmission line including said conductors, a initial balance, pickup loop I‘25' is brought into inductive coupling relation with inductor I56 of 10 driving member disposed within said second con ductor for exerting a controllable driving force the oscillation generator. The position of bo along said line, and means projecting through lometer element II5 along transmission line I03, said slot into mechanical-coupling engagement I06 as‘ well as the position of its short-circuiting with said adjustable member and said driving yoke I30 are then adjusted. to effect an impedance match between the line arrangement and the 15 member‘for effecting" a displacement of said ad justable member along said path by said driving oscillation generator for maximum power trans fer therebetween. By sliding the disc I09 to vary member. ' 2. A transmission line of adjustable electrical the position of the bolometer element with refer~ length comprising, a ?rst conductor, a hollow ence to the line conductors, an approximate or coarse impedance match is readily obtainable. 20 second conductor having an axially extending slot and a predetermined spaced relation to'said Through crank I46 lead screws I40 and MI are rotated to displace the short-circuiting yoke I30 ?rst‘ conductor, an adjustable member movable in a predetermined path in the space between as required to perfect the impedance match. said conductors for varying the electrical length It will be apparent from the adjustments de scribed that the line arrangement is similar to 25 of the transmission line including said conduc tors, a driving member disposed within said sec an adjustable transmission line terminated in an ond conductor'for exerting a controllable driving impedance element and having a stub line for force along said line, and means projecting providing impedance-matching conditions be through said slot into mechanical-coupling en tween the terminating impedance and'a circuit to which the line is coupled. In other words, that 30 gagement with said adjustable member and said driving member for effecting a displacement of portion of the line arrangement extending from said adjustable member along said path by said the connections of the bolometer element H5 driving member. ' with conductors I03 and I06 and including pickup 3. A transmission line of adjustable electrical loop I25 may be considered as a line arrange ment terminated in a resistive load. The re 35 length comprising, a ?rst conductor, a second conductor having an axially extending slot and mainder of the line arrangement between the connections to the bolometer element and the short-circuiting yoke I30 may be considered as disposed in spaced parallel relationship to ‘said arrangement I62, calibrated for direct power said adjustable member along said path by said readings, is adjusted to re-establish a balanced condition in the bridge network and provide the " desired indication of the power output of oscil driving member. ?rst conductor, an adjustable member movable in a predetermined path in the space between a stub line, adjustable to e?ect impedance matching between the composite line arrange 40 said conductors for varying the electrical length of the transmission linev including said conduc ment and oscillation generator I55. The energy tors, a driving‘member disposed within said sec transferred from the oscillation generator to the ond conductor for exerting a controllable driving - transmission line through the coupling between force along said line, and means projecting pickup loop I25 and inductor I50 causes a re sistance variation in the temperature-variable " through said slot into mechanical-coupling en gagement with said adjustable member and said bolometer element I I5 which disturbs the bal driving member for e?ecting a displacement of anced condition of'the bridge network. Resistor lation generator I55. Each of the described embodiments of the in vention features a line arrangement in which the space requirements are minimized. This‘re 4. A transmission line of adjustable electrical length comprising, a ?rst hollow conductor, a second conductor having an axially extending slot and coaxially disposed within said ?rst conduc tor, an adjustable member movable in a prede termined path in the space between said con ductors for varying the electrical length of the transmission line including said conductors, a driving member disposed within said second con ductor for exerting a controllable driving force sults from the fact that the physical dimensions of the line remain constant irrespective of the tuning adjustments. Also, in each case the driv ing member for displacingr the short-circuiting element is made of steel stock which is particu (30 along said line, and means projecting through said slot into mechanical-coupling engagement larly desirable from the mechanical standpoint, with said adjustable member and said driving while the line conductors have a construction de~ member for effecting a displacement of said ad sired to attain optimum electrical characteristics. justable member along said path' by said driving Furthermore, the driving members may be lubri member. eated as required without disturbing the con 5. A transmission line of adjustable electrical ductive characteristics of the line conductors. length comprising, a ?rst conductor, a second While there have been described what are at conductor havingv an axially extending slot and a present considered to be the preferred embodi predetermined spaced relation to' said ?rst con ments of this invention, it will be obvious to those skilled in the art that various changes and ductor, an adjustable member supported by at modi?cations may be made therein without de least one of said conductors‘ and movable there parting from the invention, and it is, therefore, along in the space between said conductors for aimed in the appended claims to cover all such varying the electrical length of the transmission changes and modi?cations as fall within the true line including said conductors, a driving member 75 disposed within said'second- conductor for exert spirit and scope of _the invention. 2,407,147 a ing a controllable driving force along said line, and means projecting through said slot into me driving member including a rotatable lead screw disposed within said second conductor for exert ing a controllable driving force along said line, and a threaded member extending from said ad justable member through said slot and meshing with said lead screw for effecting a displacement of said adjustable member along said path by chanical-coupling engagement with said adjust able member and said driving member for effect ing a displacement of said adjustable member along said one. conductor by said driving member. 6. A transmission line of adjustable electrical length comprising, a ?rst conductor, a second conductor having an axially extending slot and a predetermined spaced relation to said ?rst con 10 transmission line including said conductors, a 10 ductor, an adjustable short-circuiting member engaging each of said conductors and movable therealong in the space between said conductors for varying the electrical length of the transmis sion line including said conductors,‘ a driving ' said driving member. 10. A transmission line of adjustable electrical length comprising, a ?rst hollow axially-slotted conductor, a second axially-slotted conductor 00 axially disposed within said ?rst conductor, an adjustable member movable in a predetermined path in the space between said conductors for member disposed within said second conductor varying the electrical length of the transmission for exerting a controllable driving force along line including said conductors and having a pro said line, and means projecting through said slot jection extending through said slots of said ?rst into mechanical-coupling engagement with said and second conductors to indicate the position adjustable member and said driving member for 20 of said adjustable member, and a driving member e?ecting a displacement of said adjustable mem disposed within said second conductor for exert ber along said conductors by said driving mem ing a controllable driving force along said line ber. and mechanically engaged by said projection for 7. A transmission line of adjustable electrical e?ecting a displacement of said adjustable mem length comprising, a ?rst conductor, a second 25 ber along said path. conductor having an axially extending slot and 11. A transmission line of adjustable electrical a predetermined spaced relation to said ?rst cone length comprising, a, ?rst axially-slotted con ductor, an adjustable member movable in a preductor, a second axially-slotted conductor dis determined path in the space between said con posed in spaced relationship to said ?rst con ductors for varying the electrical length of the 30 ductor, an adjustable member movable in a pre transmission line including said conductors, a determined path in the space between said con driving member including a rotatable lead screw ductors for varying the electrical length of disposed within said second conductor for exert the transmission line including said conductors, ing a controllable driving force along said line, a pair of similar driving members disposed with and means projecting through said slot into me in said ?rst and second conductors respectively chanical-coupling engagement with said‘ adjust for individually exerting a controllable driving able member and said driving member for effect force along said line, unicontrol means for actu ing a displacement of said adjustable member ating said driving members, and means projecting along said path by said driving member. through said slots into mechanical-coupling en 8. A transmission line of adjustable electrical 40 gagement with said adjustable member and said length comprising, a ?rst conductor, a second pair of driving members for effecting a displace conductor having an axially extending slot and ment of said adjustable member along said path a predetermined spaced relation to said ?rst con by said pair of driving members. ductor, an adjustable member movable in a pre 12. A transmission line of adjustable electrical determined path in the space between said con 45 length comprising, a ?rst axially-slotted conduc ductors for varying the electrical length of the tor, a second axially-slotted conductor disposed transmission line including said conductors, a in spaced parallel relationship to said ?rst con driving member disposed within said second con ductor, an adjustable member movable in a pre ductor for exerting a controllable driving force ~ determined path in the space between said con along said line, and means secured to said ad 50 ductors for varying the electrical length of the justable member and projecting through said slot transmission line including said conductors and into mechanical-coupling engagement with said having a pair of projections extending through driving member for effecting a displacement of said slots of said ?rst and second conductors re said adjustable member along said path by said spectively, a pair of similar driving members dis driving member. 55 posed within said ?rst and second conductors 9. A transmission line of adjustable electrical respectively for individually exerting a controlla length comprising, a ?rst conductor, a second ble driving force along said line and mechanically conductor having an axially extending slot and engaged by said pair of projections for e?ecting a predetermined spaced relation to said ?rst con a displacement of said adjustable member along ductor, an adjustable member movable in a pre said path, and unicontrol means for actuating determined path in the space between said con said driving members. ductors for varying the electrical length of the NICHOLAS V. FEDO'I'OFF.