US2192494A

US2192494A - Transmission line transposition

Info

Publication number: US2192494A
Application number: US58725A
Authority: US
Inventors: Goddard De Witt Rugg
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1936-01-11
Filing date: 1936-01-11
Publication date: 1940-03-05
Anticipated expiration: 1957-03-05

Description

March 5, 1940.

DE WITT R. GODDARD TRANSMISSION LINE TRANSPOSITION I Original Fil'ed Jan. 11, 1936 Fly @2 Fly. 1

\ 09/1 07 R DOA/5'0 BY 7 INVENTOR I E Z w I ATTORNEY Patented Mar. 5, 1940 UNITED STATES PATENT oFFicE De Witt Rugg Goddard, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application January 11, 1936, Serial No. 58,725 Renewed May 18, 1939 14 Claims.

This invention relates to a new and novel transmission line transposition system which is particularly adapted to reception of short wave signals.

An object of this invention is to provide an improved transmission line having an improved spacing member or transposition block to transpose the wires in a manner to give a highly efficient transmission line.

Another object of this invention is to improve a transmission line to give a predetermined surge impedanc by changing the arrangement of the transmission block.

In the prior art it was customary to use transmission line transpositions designed to provide as low a capacity between wires as possible. However, it is occasionally desirable to provide a transmission line with a different surge impedance than that which is obtained by using the ordinary spacing members or transposition blocks for spacing the wires. In the past when a different surge impedance was required it was customary to place small evenly spaced fixed capacities or condensers across the transmission. line thereby loading the line to a new capacity value, thus resulting in a lower surge impedance.

According to my invention, the desired lower surge impedance of the transmission line is changed by obtaining the desired surge impedance directly from the transmission line spacing member itself and not obtaining it from extra capacities added to the transmission line. I propose to use several methods of changing the characteristics of the transposition blocks which are shown in the accompanying drawing in which Figure 1 is a plan view of a simple type of transmission block.

Figure 2 is a plan view partly in section of another type of transmission block similar to that of Figure 1 except that it contains a central aperture,

Figure 3 is a sectional view of a transmission block having metal plates forming condenser electrodes,

Figure 4 is a plan view of Figure 3,

Figure 5 is a perspective view of a tr'ansmission line having transmission blocks arranged to cause certain portions of the impedance of the line to vary. v

Referring now to Figure 1, a simple type of transmission block I is shown with slots la and grooves lb for retaining the conductors of a two-wire transmission line. This type of block is similar to those used in the prior art except that instead of being made of standard ceramic material such as Isolantite it is made of a new ceramic dielectric material known in the trade as Faradite which has a dielectric constant of about 80 Whereas the dielectric constant of a similar block of Isolantite has a dielectric constant somewhat less than 4. Therefore if a transmission line using number 1413 and S gauge wire is used with the ordinary spacing members the capacity between the wires would be about 2 micromicrofarads whereas if the transmission block is made of Faradite the capacity would be about micromicrofarads. Therefore the use of Faradite would change the surge impedance of the transmission line with the transposition members spaced about five feet apart from approximately 460 ohms to 200 ohms which is an exceedingly useful value particularly when receiving relatively short Wave signals.

In Figure 2 the transmission block 2 of dielectric material is shown to be of the type having a central aperture-3. According to my invention in order to change the surge impedance of the line to a lower value a plug 4 made of dielectric material having a high dielectric constant as compared with that of block 2 is arranged to fit within this aperture. Variations of the thickness of the plug 4 with respect to the thickness of the transmission block 2 and also that of the materials used in making this plug will provide a method for easily adjusting the capacity between the wires of the transmission line oiiered by the transposition. Also, variations in the diameter of the central aperture and the plugs from that of an adjacent block and plug in the transmission line will change the surge impedance of the line. These plugs may be retained within the aperture by any suitable means such as simple cementing.

In Figures 3 and 4 there is shown a transmission block similar to that of Fig. 2 except that there are provided

metallic plate members

5 and 6 which are placed each side of the plug 6 of the transmission block. These metallic plates constitute the plates of a fixed condenser and are provided with relatively short leads I and 8 which are connected to the wires 9 and In that are being transposed. Transmission line wires 8 and Ill are preferably insulated with a high grade insulation material, or may be bare wire insulated with an interposed sheet of mica between the wires and

plates

5 and 6. One of the

plates

5 or 6 may be pivotally secured by any suitable means, such as a. pin la to the iii transmission block and arranged to be moved with respect to the other plate to provide a variable condenser, as indicated by the dash and dot lines in Fig. 4.

In the transmission line shown by Figure 5 the mechanical arrangement is such that the transposition blocks are spaced apart from each other so as to gradually increase in number toward one end of the line therefore the surge impedance of the line could be made to vary, for example, between the value of ohms the impedance of a half wave doublet and 200 ohms the impedance of the pick-up or input coil of a receiver. This same result can also be accomplished by maintaining even spacing and varying the types of transmission blocks, that is, using blocks having a higher capacity at the point where the doublet antenna is to be connected.

While only a few modifications of this invention have been shown, it is to be distinctly understood that this invention may take other forms within the spirit and scope of the invention and therefore should not be limited except by such limitations as are imposed in the appended claims.

I claim:

1. A transmission line spacing and transposing member comprising a body of dielectric material, said spacing member having an aperture, a plug of dielectric material located within said aperture for changing the value of surge impedance of said line when desired, the material of said plug having a dielectric constant greater than that of said spacing member.

2. A transmission line, a spacing member for transposing said line, said spacing member being of dielectric material and having a central aperture, a removable plug of dielectric material located within said aperture for changing the value of surge impedance of said line when desired, the material of said plug having a dielectric constant greater than that of said spacing memher, the thickness of said plug having a predetermined dimension which difiers from another plug in an adjacent spacing member arranged on said transmission line.

3. A transmission line, a spacing member for transposing said line, said spacing member being of dielectric material and having a central aperture, a removable plug of dielectric material located within said aperture for changing the value of surge impedance of said line when desired, the material of said plug having a dielectric constant greater than that of said spacing member, the diameters of said central aperture and said plug having predetermined dimensions which differ from those of another plug in an adjacent spacing member arranged on said transmission line.

4. A transmission line, a spacing member for transposing said transmission line, said spacing member being of dielectric material and having a central aperture, a removable plug of dielectric material located within said aperture, the dielectric constant of the material of said plug being greater than that of said spacing member and the material of said plug having a predetermined dielectric constant which difiers from an other plug arranged on said transmission line.

5. A transmission line spacing member for transposing said transmission line, said spacing member comprising a plate of insulating dielectric material composed of at least two different solid dielectrics which are placed in collateral relationship with each other, the surge impedance of said line being predetermined by a selection of materials of different electrical properties for both solid dielectrics.

6. A transmission line spacing member comprising a plate of solid dielectric material having an aperture therein, a removable solid dielectric member arranged to fit in said aperture, the surge impedance of said line being predetermined by a selection of solid dielectric materials of different electrical properties for said removable member.

7. A transmission line spacing member com prising a plate of solid dielectric material having a central aperture therein, a solid dielectric member having a different dielectric constant from that of said spacing member and arranged to be cemented in said aperture, the surge impedance of said line being predetermined by a selection of solid dielectric materials of diiferent electrical properties for said solid dielectric member which is cemented in said aperture.

8. A transmission line spacing member in the form of a parallelepiped for transposing said line, said spacing member being of solid dielectric material and having a central aperture therein, a removable plug of dielectric material located within said aperture, a slot adjacent each one of the corners of said spacing member to retain the Wires of said transmission line, the dielectric 1 material of said plug having a dielectric constant greater than that of said spacing member.

9. A transmission line spacing member in the form of a parallelepiped for transposing said line,

said spacing member being of solid dielectric material and having a central aperture therein, a plug of different dielectric material located within said aperture, a slot adjacent each one of the corners of said spacing member and parallel with its ends to retain the wires of said transmission line, the dielectric material of said plug having a dielectric constant greater than that of said spacing member.

10. A transmission line spacing and transposition member comprising a body of dielectric material having an aperture and a removable plug of dielectric material within said aperture, the material of said plug having a dielectric constant greater than that of said body.

11. A transmission line spacing and transposition member comprising a body of dielectric material having an aperture and a plug of dielectric material within said aperture, the material of said plug having a dielectric constant different than that of said body.

12. A transmission line spacing and transposition member comprising a body of dielectric material having an aperture and a plug of dielectric material within said aperture, the material of said plug having a dielectric constant difierent than that of said body, and retaining means located on the outside contour of said body for retaining the conductors of a transmission line.

13. A transmission line spacing and transposition member comprising a body of dielectric material having a centrally disposed aperture and a plug of dielectric material within said aperture, the material of said plug having a dielectric constant different than that of said body, said body being slotted for retaining, spacing and transposing a two-wire transmission line.

14. In combination, a transmission line, a plurality of spacing members for transposing and spacing said transmission line, said spacing memof said spacing members having a predetermined dielectric constant which differs from the plug of another spacing member arranged on said line.

DE WITT RUGG GODDARD.