US1219760A - Method of and means for correcting loading-section irregularities in transmission-lines. - Google Patents

Description

.l.-.MILLS & R. S. HOYT. METHOD OF AND MEANS FOR CORRECTING LOADING SECTION IBREGULARITIES IN TRANSMISSION LINES. APPLICATION FILED SEPT. 1a. 1916.

1 ,2]. 9,760. Patented Mar. 20, 1917.

Inventors John 1111215 Ray 5. Hay! JOHN MILLS, OF WYOMING, NEW JERSEY, RAY. S. HOY'I, OF BROOKLYN, NEW

YORK, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A COR- PORATION OF YORK.

METHOD OF AND MEANS FOR CORRECTING LOADING-SECTION IRREGULARITIES IN TRANSMISSION-LINES Specification of Letters Patent. Patented Mar. 20, 191 7.

Application filed September 13, 1916. Serial N 0. 119,939.

To all whom it may concern:

Be it known that we, JOHN MILLS and RAY S. HOYT, residing at Wyoming and Brooklyn, respectively, in the countles of Essex and Kings and States of New Jersey and New York, have invented certain Improvements in Methods of and Means for Correcting Loading: Section Irregularities in Transmission-Lines, of which the following is a specification. i

This invention relates to loaded lines for the transmission of telephonic currents and more particularly it relates to means for equalizing the loading sections and for correcting transmission irregularities therein due to differences in loading sections. Its object is to provide means whereby loading sections, whose characteristics are different,

shall be rendered electrically similar, in

other words to provide means for rendering the loading uniform.

It is well known to those acquainted with the art that irregularities in loaded lines are highly objectionable and very considerably reduce the advantages accruing from the employment of loading coils. .Irre larities not only increase the attenuation and givei' 'rise to reflectional losses but also renderit very difficult to balance the line impedance with artificial lines in two-Way repeater 1 circuits, thereby limiting the amount of amplification possible without repeater singing?..

Loading irregularities may be of two kinds: -first, irregularities of the loading coils and second, irregularities of the line. It is the latter type of irregularity wh' vention. Line irregularities may be dueto diflerences in thefactual-length of loading sections; that'is the distance-between consecutiveloading coils, or may be due to different distributed line constants in the conductors of the difi'erent sections.

Practical conditions often make it very difficult to construct a loaded line system having the required uniformity of loading necessary for the best repeater operation p and the correction of irregularities by actual physical reconstruction may be very resultant capacity of th equal to that of the not expensive. It is therefore desirable to provide means for rendering the loading sections electrically uniform and equal without having recourse to physical reconstruction of the line or relocation of the loading coils. We have discovered that to secure uniformity of loading sections it is not necessary, as heretofore supposed, that the loading section's be of the same physical length and have the same distributed line constants.

- We havefurther discovered that if the total electrostatic capacity of the loalding sections be made equal by'the introduction of con-- densers between the conductors of sections having a defect of capacity, the line Will behave electrically like a uniform line and that all the advantages consequent upon uniformity of loading sectional length, Which-heretofore was secured only by careful. physical construction of the line, may

---be-rea'lized by the introduction of said condensers.

In practice the loading sections are electrically short, and the. distributed inductance ofeach line section is small compared with" the inductance of a loading coil, so that line irregularities appear in practice as differences in the line. capacity per loading section. If therefore, the capacities of the different loading sections are made equal, the line will behave electrically like auniforjmly loaded line although the various sections may differ widely in physical length and distributed constants. In the present invention lectrical uniformityloading isprovidedinserting condens in the irregular sectionsso proportione U with reference togthe capacity of the normal section and the irregular section, that the.

a1 sections: v This invention isbe'st'understoo' yreference to the accompanying drawings in which Figure his a diagranr of a. loaded transmission line with the eqlfitlizing means of this invention inserted inan irregular section; Fig. 2 isf -a diagram of-a loaded transmission line with a plurality of equalregular section is 90.

40 sections.

distributed capacity,

izing means insertedin an irregular section; and Fig. 3 1s a diagram of a cross section of a four wire phantom system -which shows the method of connecting the equalizing condensers in an irregular section of a phantom system.

Referring to Fig. 1, a transmission line is shown consisting of loading sections, 1, 2, 3, 4, the adjacent sections being connected by load coils L L L For purposes of illustration it will be assumed that the measured capacities of sections 1, 2, 4 areall equal to C which may be taken as the normal capacity per loading section of the line. Assume, however, that the capacity, measured or computed, of section 3 is C where C is less than G. Then, in accordance with this invention, a condenser 5 is connected between the two conductors of section 3, the capacity of said condenser being C-C', that is the capacity of said condenser is equal to the defect in capacity of the section in which it is connected.

It will be understood that the equalizing condenser maybe profitably inserted to increase the capacity of an irregular section whether the defect of capacity in the irregular section is due to a short loading section or, to a defect in the distributed line capacity of said irregular section. Since the capacity of condenser 5 is necessarily positive it will be seen that theequalizing or building out condenser may only be employed when there is a defect rather than an excess of capacity in the irregular section. When there are a large number of irregular sections in the line it may, therefore, be desirable to select that of largest capacity as the normal section and insert equalizing condensers in all the other If the irregularities are due to a few long sections, that is sections having an excess of said long sections maybe converted into short sections by the inser' tion of additional loading coils, and the concorrected by coll- It will thererecting irregularities in loading sections is not limitedinuts application to irregularities due to a defect of capacity in one or more sections but may be extended to the correction of irregularities due to an excess of capacity in one or more sections.

In Fig. 1 .a single equalizing condenser is illustrated. It is, of course, well understood that a single condenser does not exactly represent the eiiect of the distributed capacity of a line section. If very high precision is required, therefore, may be inserted in the irregular section, as shown in Fig. 2. 7

Referring to Fig. 2, the arrangement there The aggregate capacity are shown as inserted '11 and 12 constitute a plurality of condensers shown does not 'difier from that shown in Fig. 1, except that in the arrangement of Fig. 2 a plurality of equalizing condensers is inserted in section 3. In said figure, three condensers 6, 7 and 8 are shown, condensers 6 and 8 being preferably inserted near the ends of section 3, while condenser 7 is preferably inserted near the middle of section 3.

of said three condensers should be approximately equal to the defect in capacity of section 3.

In Figs. 1 and 2 the equalizing condensers in a loaded transmission line consisting of two parallel conductors. In phantom loaded systems wherein four parallel wires serve as the conductors for two side circuits and a phantom circuit a more complicated system of equalthe cross sections of the four wires forming the conductors of a phantom loaded system, said cross section being assumed as taken in an irregular loading section in which there is a defect of capacity both as regards the side circuits and the phantom circuit. Conductors the two conductors of one side circuit and in parallel one side of the phantom circuit; similarly conductors 13 and 14 constitute the two conductors of the other side circuit and .in parallel the other side of thephantom circuit. Condensers 15, '15, 15, 15 are connected between conductors 11 and 13, 11 and 14, 12 and 13, and 12 and 14, said condensers being preferably similar and equal. Between conductors 11 and 12 is connected a condenser 16; similarly between conductors 13 and 14 is connected a similar and equal condenser 16. As'regards the phantom circuit, conductors 11 and 12 are in parallel, constituting oneside while conductors 13 and 14 are in parallel constituting the other side of the phantom circuit. The capacity phantom circuit due to the inserted condensers is clearly seen to be 4 C where C, is the capacity of each gards each side circuit it will be readily seen that the capacity between the conductors 11 and 12 or between the conductors 13 and 14 is C i-C Where condenser 16. Let (I,, be the capacity between the sides of'the hantom circuit of the normal section and G tion. Similarly let" be the capacity between the conductors of the side circuit of as regards the-- C, is the capacity of each.-

condenser 15. As refor the irregular sec- 2 the normal section and C, for the irregular section. Then, the values of the equalizing capacities are determined by in loading sections, since, as heretofore stated, the effects of line lnductance and resistance are small. If, however, a very high degree of uniformity is required, inductance and resistance may be inserted in irregular sections -to render said irregular sections more nearly electrically equivalent to the normal section Without departing from-the spirit and scope of this invention. Furthermore, while the proportioning of the corrective capacities, as hereinbefore given, is

approximately correct, they may be proportioned more exactly, when particularly high precision is required, so as to compensate somewhat for the ignoration of the distributed line inductance. It will thus be understood that the invention is not limited to the particular proportioning of capacities given in this specification. This invention will thus be seen to be broadly directed to correcting loading section irregularities in' both two wire transmission lines and four wire phantom transmission lines and to ren- .dering an irregularly-loaded line the'electrical equivalent of a uniformly loaded line What is claimed is:

l. The method of correcting irregularities in loading sections of periodically loaded transmission lines which consists in inserting in irregular sections corrective impedances.of such value as to render the irregular section electrically equivalent to the nor-" mal' section.

2. The method of correcting irregularities in loading sections of periodically loaded transmission lines which consists in connecting across irregular sections corrective impedances of such value as to render-the resultant capacity of the irregular section equal to that of the normal section.

3. The combination of a transmission line,

and means connected across said line for correcting irregularities of loading sections said means consisting .of impedance elements having such values that the line is electrically equivalent to a uniformly loaded line.

4. The combination of a transmission line, loading coils dividing said line into sections and means connected across said line for correcting irregularities of loading sections said means consisting of condensers having such capacities that the line is electrically equivalent to a uniformly loaded line.

5. The combination of a transmission line, loading coils dividing said line into sections and means connected across said line for correcting irregularities of loading sections said means consisting of condensers having such capacities that the resultant capacities of the loading sections are equalized.

loading coils dividing said line into sections 6. The combination of a phantom transmission line, loading coils dividing said line into sections and means connected with said line for correcting irregularities of loading sectlons, sald means consistmg of lmpedance elements having such values that the line is electrically equivalent as regards both phantom and side circuits, to a uniformly loaded line.

7. The combination of a phantom transmission line, comprising four conductors,

loading coils dividing said line into sections, and, means connected between each two conductors for correcting irregularities of loading sections, said means consisting of condensers having such capacities that the line is electrically equivalent as regards both phantom and side circuits, to a uniformly loaded line.

In testimony whereof, we have signed our names to this specification in the presence of a subscribing witness, this sixth day of September 1916;

JOHN MILLS. RAYS. HOYT.

JoH N Oiinsoir.

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