US2511524A - Capacitative coupling device - Google Patents

Description

June 13, 1950 B. ADLER 2,5l1,524

CAPACITATIVE COUPLING DEVICE Filed April 6, 1949 'NVENTOR ezy'ma'n, Adler @M Mgg@ atented `une UNITED STATES PATENT OFFICE 2,511,524 cAPACrrA'rIvii` COUPLIG nevica' Benjamn Adler, White Plains, N; Y.' Application April 6, 1949, Serial No. 851737 17 Claims. l

This invention relates to coupling devices more particularly of the type including a capacitative pick-up member for transferring radio frequency energy from along the length of a coaxial cable transmission line to a radio frequency receiver.

Where a coaxial cable transmission line is tapped at various places along the length thereof to transfer energy from the line to radio frequency receivers such as, for example, television receivers, if the tap should cause any change in the spacings of the conductors, as the value of the characteristic impedance of the line at the tap would change, this would cause an impedance discontinuity in the line. Such impedance discontinuity would cause reflection of the signals passing along the line with resultant standing waves and consequent loss of energy and distortion of the signal.

This loss of energy may cause such a weak signal to be transferred to the radio frequency receiver that the signal to noise ratio would be very low with resultant unsatisfactory functioning of the receiver. Moreover such defect Would be aggravated Where several receivers are tapped in along the length of the line, for due to the plurality of impedance discontinuities, successive receivers would receive less and less energy with the result that they would function in an unsatisfactory manner or not at all.

With these fundamental concepts of transmission line theory in mind, it is to be noted that Where a direct connection is to be made to the conductors of the coaxial cable along the length thereof, it is necessary that a portion of the outer insulating casing rst be removed, the outer conductor severed and pushed apart to aord access to the dielectric casing in which the inner conductor is embedded, and such dielectric casing must then be cut away so that a lead may be soldered or otherwise affixed to the exposed inner conductor.

After this is done, the dielectric casing and outer conductor must be restored so that they have substantially their original physical characteristics, for as the coaxial cable is symmetrical along its entire length, if the thickness of the dielectric casing is changed, as by melting because of the heat evolved during the soldering operation, or if the soldering should increase the diameter of the inner conductor at the joint, the spacing between the conductors would be changed and an impedance discontinuity would result with the attendant disadvantages heretofore pointed out.

When conventional T-couplings are used to tap into the coaxial cable, the latter must be coinpletely severed, and precise soldering must be done, without undue heating of the dielectricV casing, to aflix the individual conventional coaxial connector required at each end of the severed cable in order to join them to the T- coupling. The soldering operations are relatively delicate to perform and time consuming and would require the services of a skilled radio technician and at best the coupling may still cause an impedance discontinuity in the line with the resultant reflections and standing waves on the line heretofore pointed out.

It is accordingly among the objects of the invention to provide a device of the above typeY impedance discontinuity in the line at the point of transfer and consequent minimum amount of reiiection and standing waves on the line and hence a minimum loss of energy.

Another object is to provide a device of the above type that is simple in structure and relatively inexpensive to manufacture, having but few parts which are sturdy and not likely to become out of order and for its intended time.

According to the invention from its broader aspects, the transfer of the signal voltage from along the length of the coaxial transmission line to the radio frequency receiver is accomplished by means of a coupling device including a pickup member, placed against the dielectric casing of a section of the line from which the outer inwhich may be assembled purpose in a relatively short sulating covering has been removed and the outer conductor severed to expose such dielectric casing, to form an electric capacitor with respect to the inner conductor of the line.

The capacitative be in the form of a shell, desirably has an inner diameter substantially the same as that of the outer conductor so that it will snugly encomv1 pass the dielectric casing `and be flush therewith. In order to close the break in the outer conductor and to provide electrical continuity therepick-up member, which may 1y of, a conductive structure is provided having a portion thereof extending parallel to the shell and spaced therefrom, means being provided on said structure to connect the severed ends of the outer conductor thereto. The structure is of such dimensions and so constructed and arranged that the pick-up member and said parallel portion will constitute a section of transmission line having a characteristic impedance substantially equal to that of the coaxial cable transmission line, thereby avoiding any 'substantial impedance discontinuity in the line due to the interposition of the coupling device.

More specifically, according to one` aspect of the invention, the conductive structure may comprise a pair of substantially identical trays, each V having a semi-cylindrical floor thereinf'which floors when the trays are juxtaposed,Y form a' cylindrical cavity, and means are desirably provided at each end of the trays and in communi; cation with the floors thereof, to which, when suchftrays 'are' juxtaposed, the severed ends of the outer conductor may be afxed and through which'the dielectric casing may extend.

'The c'apacitative pick-up member associatedv with said conductive structure may comprise a pair of` semi-cylindrical shells affixed respectively on the floors of said trays and each desirably slightly less than a semi-circle in cross section so thatthe longitudinal edges of the shells may be' 'slightlyf spacedfrom each other when the trays Vare juxtaposed with said shells clamped againstsaid dielectric casing.

In the accompanying drawings in which are shown one' or'm'ore of various possible embodiments of the several features of the invention,

Fig. 1 is Van exploded perspective view of the device and the coaxial cable with the latter pre-r pared for mounting of said device,

Fig. 2 isa longitudinal cross sectional view of Y the device'mounted on the coaxial cable,

YFig'. 3 is a diagrammatic View showing a receiver connected to the device, and

--Figl 4' is an equivalent circuit showing the device mounted on a transmission line and a receiver connected thereto.

Referring now to the drawings, the coupling device comprises a capacitive pick-up member I I and a conductive structure I2 in whichr said member may be positionedl The pick-up member desirably comprises two substantially semi-cylindrical shells or plates 2| and 22 of 'conductive material having a radius of curvature substantially the same as that of the dielectric casing I3 so that the latter may be interposed between such shells. Each shell desirably Nis slightly less thanV a semi-circle in cross` section so that a narrow gap 23 may be provided between 'each of the Ylongitudinal edges 24, 24' of the' shells when they are positioned around dielectrlccasing |3.

ln Vorder to retain the shells 2|, 22 snugly against said dielectric casing I3, the conductive structure I2 desirably comprises two identical trays 25, 2t, which may be cast or otherwise formed from any suitable metal.

Although Vthe shape of the exterior of the trays drical cavity 32 Iwill be formed, dowel means 33 being provided to insure accurate alignment of said floors 28.

Each of the trays desirably has a plurality of insulating grommets 38, illustratively two in number, extending through the base 39 of the tray and securely affixed in said base.

Although any suitable means could be used to affix the shells 2|, 22 to their associated pair of grommets 33, in the embodiment herein shown, a plurality of spring spacerse!! are provided, illustratively two in number, for each of said shells. lach spacer 40 desirably comprises a reversely bent strip lof resilient conductive material having one of the legs 4| thereof affixed as by soldering or welding to the convex surface of the associated shell. The other or outer leg 42 of the spacer desirablyhas a threaded stud 43 aiiixed thereon, extending outwardly therefrom, at right angles thereto. The spacers on each of the shells are so separated that thestuds thereon may be inserted through the grommets 38 in the trays 25, 26 respectively, `and are` retained in place by nuts 44 screwed on the ends of the stud projecting from the outer end of the grommets.

By means` of such construction when the trays are juxtaposed as heretofore described, with the shells 2|, 22 positioned around the dielectric casing I3, the springV spacers 49 will be slightly com-V pressed, resiliently urging the shells against said casing I3 which will be encompassed by said shells.

In order that the shells 2|, 22 be electrically insulated vfrom the trays 25, 2S, the length thereof isrslightly less than that of the semi-cylindrical floors 28 in said trays, providing a gap 45, between the ends of the shells and the associated end Walls 23', 3| of the trays.

To provide for electrical continuity between the ends I B,` I9 of the severed outer conductor l1, meansare provided to connect such ends to the associated ends 'of'the conductive structure or' s formed'integrally with the ends of each of the fifi trays respectively and extending outwardly therefrom. Each connector member has a semi-cylindrical troughV 48` therein of diameter substantially the same as the diameter of the casing vI3. Troughs 43 are'coaxial with oor 28 of the associatedftray' and are 'in'communication with said floor 234through 4a semi-circular notch 49 in each of theend walls 25 rand 3| which notches 49"` have the same diameter as trough 48.

The troughs 4 3 in lthe connector member 46,

4l are sorposiftioned with respect'to the iioor` 28r of the associated Vtray that'when the trays are, juxtaposed, with the shells 2l, 22 therein encompassing casing I3, theminner surfaces of the troughs 48 inthe connector members, will be longitudinally alignedwith theinner surface of" the shells, thereby ensuring that the dielectricy casing I3 will'be resting-against the inner surfaces of troughs 48,"which form a bore 59, and againstv the inner surfaces of shells 2|, 22.

Preferably each of theconnector members 46, 41 at its root end has a semi-cylindrical ledge 5| and the thickness of the connector member is gradually reduced from said ledge 5| to thenose end 52 thereof, tapering to substantially a knife edge thereat, with "the outerv diameter of said knife edge 52 lbeing substantially the same as the inner diameter 'of the'outer conductor Il. To installnthe device: it is first necessary to prepare the coaxial cable I by removing a small section of the outer covering I6 thereof of length slightly greater than the overall length of the housing I2 including the connector members 45, 41. The exposed outer conductor I1 is severed in the mid portion thereof without cutting the dielectric casing I3 therebelow and each of the severed ends I8 and I9 of said outer conductor is pushed back as shown in Fig. 1. This will cause the braided outer conductor to flare out as at I1 so that it Will be of greater diameter at its severed ends.

One of the trays, illustratively tray 26, with a, shell 22 mounted therein as heretofore described, is thereupon positioned about the coaxial cable so that the exposed dielectric casing I3 rests on the associated shell 22 and in the troughs 48 in connector members 46, 41, with the knife edges 52 at the noses of such members 46, 41 extending between the outer conductor I1 at the severed end thereof and the dielectric casing I3'. This procedure is repeated with the other tray 25, the dowels 33 aligning such trays when they are juxtaposed.

The flared ends of the outer conductor I1 are thereupon pushed up on the juxtaposed connector members which form a frusto-conical contour, until the ends I8, I9 of the outer conductor I1 are on the associated ledge 5I. By means of any suitable clamp means 55 positioned around the root ends of the juxtaposed connector members, over the ends I8', I9 of the outer connector I1 and the ledge 5I, the ends I8, I9 may be securely retained against their associated ledge 5I, the clamp also securely retaining the juxtaposed trays 25, 26 together.

As the knife edges 52 of the connector members extend between the flared portions I1' of the outer conductor I1 and the dielectric casing I3 to contact the innei` surface of such Outer conductor as at 56 Where it has substantially its original diameter, and as the inner surface of the shells 2I and 22 are aligned with the inner surface of said troughs in the connector members, it is apparent that for all practical purposes, the casing i3 will have an outer conductor therearound the distance of which, from the inner conductor I4, will not be varied by the interposition of said coupling unit. As the electrical continuity of the outer conductor is provided by the housing itself, and as the inner conductor I4 is not physically disturbed by the coupling device, the `gaps 45 between the shells 2I, 22 and the housing, will have negligible effect in producing an impedance discontinuity in the coaxial cable I5.

The coupling device itself essentially comprises a section of coaxial transmission line interposed in the main line with the shells 2 I, 22 forming the inner conductor and the wall of the cavity 32 forming the outer conductor. It is important that the characteristic impedance of the coupling device be substantially the same as that of the line to prevent impedance discontinuity.

As the diameter of each 0f the shells 2|, 22 is determined by the diameter of the casing I3 which they straddle it is only necessary to determine the inner diameter of the floors 28 which, when juxtaposed, form the cylindrical cavity about the shells 2 I, 22. This may readily be calculated from the formula Z0: 10g10 all Awhere Z0=characteristic impedance of the line.

=inner diameter of the outer conductor and a=outer diameter of the inner conductor. Assuming the cable to have a characteristic impedance Z0 of 52 ohms and the outer diameter a of the shells to be .34 inch, we find or b=2.4 .34=.82 inches, which is the required diameter of floors 28 so that the coupling device will have a characteristic impedance of 52 ohms.

A radio frequency receiver may be connected to the coupling device as shown in Fig. 3 by attaching one of the leads i. e. lead 60 from the receiver 62, to the projecting end of a stud 43 on one of the shells and by connecting the other lead, i. e. lead 6I, to the housing I2. As the shells 2|, 22 are electrically insulated from each other, one of them may be used to couple energy to one unit and the other to couple energy to another unit (not shown). As only a portion of the energy in the transmission line I5 is generally required to actuate the receiver 62 a series resistance R may be inserted in one of the feeder leads, illustratively lead 60 as shown in Fig. 4.

The following are typical calculations to determine the value of R at megacycles which is illustratively chosen as the mid point of the frequency range at which at receiver, such as a television set, is to operate.

Where, for example, it is desired that voltage fed into the receiver 62 be 30 decibels less than the voltage across the transmission line, the impedance Zp looking into the feeder leads 60, 6I at the receiver toward the coupling device should be approximately 31 times the characterisic impedance Zo of the tranmission line itself.

Assuming the characteristic impedance Z0 of the transmission line to be 52 ohms, its capacitance per foot is known to be approximately 29 mmf. Assuming the length of the pick-up shells to be two inches each, then the capacitance of the pick-up member will be or approximately 5 mmf.

At 100 mc., the capacitance reactance Xe of the pick-up member can readily be ascertained by the formula 1 Zc-m when f=frequency in megacycle and c=capaci tance in mmf., and is found t0 be approximately 320 ohms.

Applying conventional formulas then and R is found to be approximately 1530 ohms.

Since R is large as compared to XC, Zp will not vary appreciably over the range of frequencies from 50 mc. to 200 mc. thereby assuring almost constant signal voltage transfer to a television receiver at all frequencies in this range.

If desired resistor R may be eliminated if the shells are constructed of resistive material such as carbon or nichrome. The equivalent electrical circuit will still be such that a resistor will appear in series with the pick-up producing the required isolation.

With such coupling device, long runs of line may be used between the coupling device and a receiver with no effect on the main transmission line on which the coupling device is mounted and a short circuit between theshells 2i and 22 and the outer conductor Il or the housing', either in the device itself or external' to it'will not aiect the signals passing hrough the ttrans'missionline I5 for such short circuit will merely electrically restore the line to its original form and only disable the receiver connected tothe 'defective coupling device.

The number of receivers that may beA fed from a distribution line utilizing the coupling 'device herein described is limited mainly by the length of the line, as discontinuity losses in the 'line produced by the tapping in of suchreceivers is kept ata minimum.

Because the device is capacitive, more voltage will? be transferred to the receivers at high frequencies than at low frequencies hence automatically compensating for the greater losses in the line at such higher frequencies.

Asthe coupling unit maybe added to the line with but a few operations without-need for cutting the dielectric casing or inner conductor and Without need for soldering-theaddition of such device is a relatively simple procedure that does not require the services of a 'slrilled'radio 'me'- chanic but may be performed by any electrician.

As many changes couldfbe made in the above construction, and many 'apparently widely 'different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown'in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

`Having thus described my invention, what I claim as new and desire to'secure 'by Letters Patent of the United States is:

1. A device for transferring energy from along the length of a coaxial cable transmission line, said device comprising a capacitative pick-up member adapted to encompass and extend longitudinally of the dielectric casing of such .cable from which a portion of the outer covering has been removed and the outer conductor severed to expose such dielectric casing, means to retain said pick-up member against such dielectric casing, a conductive structure having a portion thereof extending parallel to said pick-upmember and spaced therefrom, said parallel extending portion and said pick-up memberbeing spaced so as to form a section of transmission line having the same characteristic impedance as the coaxial cable to which the device -is aixed, and means to connect the severed ends of such outer conductor to said structure.

2. The combination set forth in claim 1 in ywhich said pick-up member comprises a plurai- :ity of substantially semi-'cylindrical shells of con- .riuctive material.

3. A device for transferring energy from along the length of a coaxial cable transmission line, said device comprising a capacitative pick-up member' adapted to encompass and extend longitudinally of the dielectric casing `of ,such cable from which a portion of the outer covering has been removed and the outer conductor severed `to expose such dielectric casing, and a conductive structure having a cylindrical cavity vvtherein encompassing said pic'x-up member and coaxial therewith, the wall of said cavity and said pickup member being spaced so as to form 2, section of transmission line having the same characteristic impedance as the coaxial cable to which the device is affixed, saidstructure having means thereon for connection thereto of the severedlends Qiihgouter QQnCluCtQr.- Y

'4. The combination set forth in claim 3 which vmeans are provided on said pick-up member coacting with said structure and insulated therefrom securely to retain said pick-up mem ber against such dielectric casing.

5. A device for transferring energy from along the length of a coaxial cable transmission line, said device Comprising a capacitative, substantially cylindrical pick-up member adapted to encompass and extend longitudinally of the dielectric casing of such cable from which a portion of the outer covering has been removed and the outer conductor severed to expose such dielectric casing, said pick-up member having an inner diarneter substantially the same as that of such outer conductor, a housing of conductive material having a cylindrical cavity therein encompassing sailrpiclg-up member and coaxial therewith, the wall of s aid cavity and said pick-up member being spaced so as to form a section of transmission line having the same characteristic impedance as the coaxial cable to which the device is aflixed, means on said pick-up member coacting with said housing and insulated therefrom securely to retain said pick-up member against such dielectric casing and means on said housing or connection thereto of the severed ends of the outer conductor.

6. The combination set forth in claim 5 in which said last named means comprises a pair of frusto-conical conductive members extending longitudinally outward from said housing at each end thereof and rigid therewith, said members eachlhaving a bore therethrough 'coaxial with said cylindrical cavity and of diameter substantially equal to that of such dielectric casing, which casing extends through said bore, whereby said fijnste-conical members may be positioned be@ tween the severed ends of the outer conductor reg spectively and the dielectric casing, and 4clamp means are provided associated with each of said trusteconical members respectively, to ax the sev-ered ends of such outer conductor thereto.

7. The combination set forth in claim 5 in which said last named means comprises a pair of truste-conical conductive members extending longitudinally outward from said housing at each end thereof and rigid therewith, said members Qih having a bore therethrough coaxial with said cylindrical cavity and of diameter substantially equal to that of such dielectric casing, which casing extends through said bore, said frusto-conical members each having a ledge portion at the root end thereof and substantially a knife edge at the nose end thereof, whereby said frusto-conical members may be positioned between the severed ends of the outer conductor -respectively and the dielectric casing, With said severed ends respectively resting on an associated ledge and clamp means are `provided asso-.- cated with each of said frusto-conical members respectively to alhx the severed ends of such outer conductorthereto, said knife edge of said frusto.- conical members having an outer diameter substantially the saine as the inner diameter of such outer conductor.

8. A device for transferring energy from along the-length of a coaxial Vcable transmission line, said device comprising a capacitative, substantially cylindrical pick-up member adapted toencompass and extend longitudinally of thev ydielectric casing of such cable from which a portion of the outer covering has 'been removed and the outer conductor severed to expose such dielestricaiea Said pivkfupmember having an curely to retain said inner diameter substantially the same as that of :such outer conductor, a housing of conductive material, means on said pick-up member coacting with said housing and insulated therefrom sepick-up member against such dielectric casing, said housing comprising a pair of substantially identical trays each having a body portion with a longitudinal semi-cylindrical floor therein, which iloors when said trays are juxtaposed, form a substantially cylindrical cavity vencompassing said pick-up member and coaxial therewith, the wall of said cavity and said pickup member being spaced so as to form a section of transmission line having the same characteristie impedance as the coaxial cable to' which the device is affixed and means on said housing for connection thereto of the severed ends of the outer conductor.

9. A device for transferring energy from along the length of a coaxial cable transmission line, said device comprising a capacitative, substantially cylindrical pick-up member adapted to encompass and extend longitudinally of the dielectric casing of such, cable from which a portion of the outer covering has been removed and the outer conductor severed to expose such dielectric casing, said pick-up member having an inner diameter substantially the same as that of such outer conductor, a housing of conductive material, means on said pick-up member coacting with said housing and insulated therefrom securely to retain said pick-up member against such dielectric casing, said housing comprising a pair of substantially identical trays, each having a body portion with a longitudinal semicylindrical floor therein, said floors having a greater diameter than said pick-up member, and a pair of substantially identical connector members of conductive material extending longitudinally outward from the tray at each end thereof respectively and rigid therewith, said connector members each having a semi-cylindrical longitudinal trough therein in communication with the semi-cylindrical floor in said body portion and coaxial therewith and of diameter substantially equal to that of the dielectric casing, whereby when said trays are juxtaposed and positioned about said pick-up member, the semicylindrical floors of the body portions will form a cylindrical cavity encompassing said pick-up member and the troughs in said connector members will form a bore through which the dielectric casing may extend, the wall of said cavity and said pick-up member being spaced so as to form a section of transmission line having the same characteristic impedance as the coaxial cable to which the device is ailixed and means coacting with the juxtaposed connector members to aillx the severed ends of such outer conductor thereto.

10. The combination set forth in claim 9 in which said connector members each have a ledge portion at their root ends and taper to substantially a knife edge at their nose ends and the severed ends of such outer conductors are flared from the ends of the portions of such cable from which the outer covering has been removed, whereby when said connector members are juxtaposed, associated pairs thereof may be positioned between the severed ends of the outer conductor respectively and the dielectric casing, with such severed ends resting on said ledges respectively and said knife edge nose extending to the ends of the portion of the cable from which the outer covering has been removed and in engagement with the inner Wall of such outer conductor and 10 provided lcoacting with said securely to retain such severed -clamp means areledges respectively, ends thereagainst.

l1. A device for transferring energy from along the length of a coaxial cable transmission line, said device comprising a capacitative pick-up member including two substantially semi-cylindrical shells, each having a radius of curvature substantially equal to that of the dielectric casing of such cable from which a portion of the outer covering has been removed and the outer conductor severed to expose such dielectric casing, a housing of conductive material having a cylindrical cavityv therein, means on said shells coacting withsaidhousing and-insulated therefrom securelyto retain said shells against such dielectric casing extending longitudinally thereof with said cylindrical cavity encompassingsaid pick-up member and coaxial therewith, the wall of said cavity and 'said pick-up member being spaced so as to form a section of transmission line vhaving the same characteristic impedance as the coaxial cable to which the device is affixed, and means on said housing for connection thereto of the severed ends of the outer conductor.

12. A device for transferring energy from along .the length of a coaxial cable transmission line, said device comprising a capacitative pick-up member including two substantially semi-cylindrical shells, each having a radius of curvature substantially equal to that of the dielectric casing of such cable from which a portion of the outer covering has been removed and the outer conductor severed to expose such dielectric casing, a housing of conductive material, means on said shells coacting with said housing and insulated therefrom securely to retain said shells against such dielectric casing, said housing comprising a pair of substantially identical trays each having a body portion with a longitudinal semicylindrical floor therein, said floors having a greater diameter than said pick-up member, which iloors when said trays are juxtaposed form a substantially cylindrical cavity encompassing said pick-up member and coaxial therewith, the Wall of said cavity and said pick-up member being spaced so as to form a section of transmission line having the same characteristic impedance as the coaxial cable to which the device is affixed, and means on said housing for connection thereto of the severed ends of the outer conductor.

13. A device for transferring energy from along the length of a coaxial cable transmission line, said device comprising a capacitative pick-up member including two substantially semi-cylindrical shells, each having a radius of curvature substantially equal to that of the dielectric casing of such cable from which a portion of the outer covering has been removed and the outer conductor severed to expose such dielectric casing, a housing of conductive material, means on said shells coacting with said housing and insulated therefrom securely to retain said shells against such dielectric casing, said housing comprising a pair of substantially identical trays, each having a body portion with a longitudinal semi-cylindrical iloor therein, said floors having a greater diameter than said pick-up member and a pair of substantially identical connector members of conductive material extending longitudinally outward from the trays at each end thereof respectively, said connector members each having a semi-cylindrical longitudinal trough therein in communication with the semi-cylindrical floor in said body portion and of diameter substantially 'equal to that oi Itl'lefdielectricV casing,l whereby Awhen'/-said-traysare juxtaposed land positioned about said pick-up member, thef-semi-cylndrical "iioors'f in the body portionswll form a' cylindrical cavity'fencompassir'ig said` v pick-up member and the troughs in said connector 1members-wi1l form a bore through which the dielectric casing may extend, the-Wall of said cavity and said pick-up memberfbeing spaced so as to 'form a section of transmission line havingy the A-sarne characteristic impedance'as the coaxial cable to .Which'the devvice is aflixed'and meanscoacti-ngwith the juxta- Y posed'connector membersto'aflixthe-severed ends of such outer conductor thereto. 14; The combination set forth in= claim-13 'in which each ofv said shells is slightly'less than a usemicirclel -in cross 'section and the Y longitudinal e'dgesoi` said shellsare spaced from each other when retained against' suchdielectric casing.

'515'. The combination setforth in* claim 13 in Which'saidfshel-ls are `of highly resistivematerial, 16,1 4The combination set'iorth in claim 13`in which-the means'on said shells to retain the latter Vhasibeen removed and they Vouter conductor severedgto expose the'dielectricicasing'in which the inner conductor is embedded, ai coupling. device comprisinga capactative pick-up member havingta 'generallyv cylindrical shell encompassing such AVexposed dielectric casing and spaced from said outerV conductor to form an electric condenser-with'respectlto the inner conductor, and a; conductive structure electrically connecting'the severedends ofsuch "outer conductor, extending parallel to v'said vshell and spaced therefrom "so as to' forma section Vof transmission line having substantially the same vcharacteristicimpedance as such coaxial cable; whereby when a radio frelquencyreceiver isv connectedto vsaid conducting -structure'a-nd sai-dY shell, energywill be transferred'irom said-coaxial cabletosuch receiver without any substantial impedance'discontnmity inf-said coaxial cable:

BENJAMIN ADLER.

REFERENCES CITED YThefiollovving references are of recordin the iile'of this patent:

UNITED STATES PATENTS Number Name Date 1,708,292 Buysv Apr. 9, 1929 21,092,647 Hobart Sept. '7, 1937 2,442,614 Norton June 1, 1948 2,451,868 v.Quackenbush- Oct. '19, 1948

Images