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1、BRITISH STANDARD BS 5425-1: 1986 Coaxial cable for wideband distribution systems Part 1: Specification for single unit, semi-airspaced cables for wideband distribution systems UDC 621.315.212:621.316.1 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy,
2、 (c) BSI BS 5425-1:1986 This British Standard, having been prepared under the direction of the Electronic Components Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 January 1986 BSI 06-1999 First published February 1977 First revision January 19
3、86 The following BSI references relate to the work on this standard: Committee reference ECL/6 Draft for comment 84/23910 DC ISBN 0 580 14830 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Electronic Components Standards Committee (EC
4、L/-) to Technical Committee ECL/6 upon which the following bodies were represented: British Plastics Federation British Telecommunications plc Crown Agents for Oversea Governments and Administrations Electric Cable Makers Confederation Home Telephone Cable Makers Association Ministry of Defence Soci
5、ety of British Aerospace Companies Limited The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Broadcasting Corporation Cable Television Association of Great Britain Cable Television Cable Makers Association Confederation of Aerial In
6、dustries Department of Trade and Industry (British Calibration Service) ERA Technology Ltd. Electronic Components Industry Federation Electronic Engineering Association Society of Cable Television Engineers United Kingdom Atomic Energy Authority Amendments issued since publication Amd. No.Date of is
7、sueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5425-1:1986 BSI 06-1999i Contents Page Committees responsibleInside front cover Forewordii Section 1. General 1Scope1 2Definitions1 Section 2. Constructional requirements 3Materi
8、als2 4Dimensions3 Section 3. Electrical requirements 5Mean characteristic impedance (Zm)5 6Attenuation5 7Uniformity of characteristic impedance5 8Screening effectiveness5 9Conductor d.c. resistance5 10Insulation resistance5 11Sheath spark test5 Section 4. Mechanical requirements 12Bending7 13Longitu
9、dinal pull of conductors other than copper covered steel conductors7 Section 5. Identification, labelling and packaging 14Identification8 15Labelling8 16Packaging8 Appendix A Recommended schedule of testing9 Appendix B Mechanical test methods9 Appendix C Electrical test methods11 Figure 1 Attenuatio
10、n measurement: substitution method16 Figure 2 Attenuation measurement: power ratio method16 Figure 3 Uniformity of characteristic impedance measurement: sweep frequency: return loss bridge method16 Figure 4 Surface transfer impedance apparatus for frequencies up to 30 MHz17 Figure 5 Surface transfer
11、 impedance apparatus for frequencies above 30 MHz18 Table 1 Resistance factor and minimum elongation for conductors2 Table 2 Overall diameter and diameter over dielectric3 Table 3 Minimum sheath thickness4 Table 4 Mean characteristic impedance5 Table 5 Maximum attenuation5 Table 6 Minimum return los
12、s6 Table 7 Maximum surface transfer impedance6 Table 8 Maximum conductor d.c. resistance6 Table 9 Minimum pulling force for 3 % length extension at 20 5 C7 Table 10 Minimum barrel dimensions (coiling and drumming diameters)8 Table 11 Mandrel diameters for bending tests10 Publications referred toInsi
13、de back cover Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5425-1:1986 ii BSI 06-1999 Foreword This revision of this British Standard has been prepared under the direction of the Electronic Components Standards Committee to take accoun
14、t of technical changes occurring since publication of the 1977 edition. This British Standard caters particularly for the immediate requirements of expanding cable television networks, and its scope has been for that reason confined to the types of cable required urgently. It is recognized that othe
15、r types of cable may be required in due course and it is planned for further Parts of BS 5425 or other standards to be prepared to cater for these. Certain of the performance requirements of this standard may require early amendment following practical experience of use of these cables in cable tele
16、vision networks. For the successful operation of wideband distribution systems, coaxial cables are required to comply strictly with the quality and performance requirements of the standard. For this reason, manufacturers of these products are advised to commission and maintain satisfactory systems i
17、n accordance with BS 5750, or advised to seek certification of their products and/or Quality Assurance systems (as required) from the British Approvals Service for Electric Cables (BASEC). A British Standard does not purport to include all the necessary provisions of a contract. Users of British Sta
18、ndards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 18, an inside back cover and a back cover. Thi
19、s standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5425-1:1986 BSI 06-19991 S
20、ection 1. General 1 Scope This Part of BS 5425 specifies the constructional, electrical and mechanical requirements for a series of single unit, semi-airspaced coaxial cables primarily intended for use in the frequency band 5 MHz to 1 000 MHz. Cables with and without separate moisture barriers are i
21、ncluded. This specification excludes designs having cellular foam dielectrics. Appendix A gives a recommended schedule of testing. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 5425 the definitio
22、ns given in BS 2316-1 and BS 4727-3: Group 01 apply. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5425-1:1986 2 BSI 06-1999 Section 2. Constructional requirements 3 Materials 3.1 Inner conductor 3.1.1 General. The inner conductor shall
23、 be one of the following: a) a single annealed copper conductor complying with BS 4109; b) a single copper covered steel conductor complying with 3.2 of BS 2316-1:1968 and BS 2316-2:1968; c) a single copper covered aluminium conductor complying with clause 5 of BS 6360:1981. Completed cable shall no
24、t contain joints in the inner conductor which have been made subsequent to the final wire drawing operation. 3.1.2 Resistance factor. The maximum resistance of copper covered steel conductor or copper covered aluminium conductor shall be that given for copper conductors in BS 4109 multiplied by the
25、appropriate resistance factor given in Table 1. 3.1.3 Elongation 3.1.3.1 Minimum elongation. The minimum percentage elongation of a sample of inner conductor removed from the finished cable shall be not less than the value given in Table 1 when tested in accordance with BS 4109 and BS 6360. 3.1.3.2
26、Measurement of elongation at break. Elongation due to the breaking of the wire in tension shall be measured by means of an extensometer or other device suitable for measuring elongation in samples up to 250 mm in length and having a vernier reading to 0.25 mm attached to the test specimen. A tension
27、 load of approximately 10 % of rated strength shall be applied to the specimen. The elongation shall be observed as the tension load is increased and the reading when fracture occurs shall be the elongation. Tests in which the elongation is less than that specified but in which the fracture occurs w
28、ithin 25 mm of the jaws or extensometer clamps shall be disregarded. Table 1 Resistance factor and minimum elongation for conductors 3.2 Dielectric The dielectric shall be of a plastics/air construction comprising an insulating tube at the centre of which the inner conductor is supported such that t
29、he cable complies with the electrical and mechanical requirements given in sections 3 and 4. Where polyethylene is used it shall be of type 03 or type 2 of BS 6234 without pigmentation. 3.3 Outer conductor The outer conductor shall consist of either of the following alternatives. a) A metal tape or
30、tapes, covered by a metal braid or helix. This shall be a plain annealed copper tape or plain annealed copper tapes with properties complying with BS 4608, except for those parameters (e.g. sizes) specified otherwise in this standard. The inner tape shall be applied longitudinally with a minimum ove
31、rlap of 2.5 mm and shall be of minimum thickness 0.022 mm. Additional tapes shall be applied either longitudinally or helically lapped. An additional screen of copper wires, complying with BS 4109, except for those parameters (e.g. sizes) specified otherwise in this standard, shall be applied in con
32、tact with the outermost tape or tapes such that the completed cable complies with the electrical and mechanical requirements of this standard. Where these wires are applied in the form of a braid, this shall have a filling factor of not less than 0.3, where the filling factor (kf) is calculated as f
33、ollows: NOTEThe relationship between filling factor and coverage factor is: Coverage factor = 2 kf kf2 MaterialResistance factor Minimum elongation % Copper Copper covered steel Copper covered aluminium 1.0 3.5 1.8 8 1 10 where mis the total number of spindles; nis the number of ends of wire per spi
34、ndle; Dis the mean diameter of braid = diameter over dielectric + 2.25 dw; dwis the diameter of braid wire; Lis the lay length of braid. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5425-1:1986 BSI 06-19993 Where these wires are applie
35、d in the form of a single layer of helically applied wires, this shall have a coverage factor of not less than 0.5, where the coverage factor is calculated as follows: b) A metal tape or tapes, not covered by a metal braid or helix. This shall be a plain annealed copper tape or plain annealed copper
36、 tapes with properties complying with BS 4608 except for those parameters (e.g. sizes) specified otherwise in this standard, of minimum thickness 0.15 mm, applied longitudinally with a minimum overlap of 3.5 mm such that the completed cable complies with the electrical and mechanical requirements of
37、 this standard. 3.4 Outer sheath The outer sheath of the cable shall be of plastics material. Where polyethylene is used it shall be of types 03C or 2C of BS 6234. Where PVC is used it shall comply with the requirements of BS 6746, type TM 1 or type 6. 3.5 Moisture barrier Where a moisture barrier i
38、s required a further metallic layer shall be incorporated under the sheath. Initially an insulating layer of non-hygroscopic tapes shall be applied either longitudinally or helically over the outer conductor. This shall act as a bedding for a longitudinally-applied laminated tape of aluminium foil c
39、oated with a polymer, with the latter towards the outside. The aluminium foil shall have a minimum thickness of 0.075 mm for cables with a maximum specified overall diameter of 12 mm or less and a nominal thickness of 0.15 mm for diameters above 12 mm. The sheath shall be bonded to the polymer coati
40、ng of the laminated tape. NOTEFor additional protection, additional layers of either metal or plastics may be applied if requested by the user. 4 Dimensions 4.1 Diameter over the dielectric When measured in accordance with B.1, the mean diameter over the dielectric shall comply with the appropriate
41、value and tolerances given in Table 2. 4.2 Overall diameter When measured in accordance with B.2, any single measurement of overall diameter shall be less than the maximum overall diameter given for the appropriate cable in Table 2. 4.3 Sheath thickness When measured in accordance with B.3, the shea
42、th, including the moisture barrier where applicable, shall have a minimum thickness at any point in accordance with Table 3. 4.4 Ovality When measured in accordance with B.4, the ovality of both the dielectric and the sheath shall be not greater than 5 %. Table 2 Overall diameter and diameter over d
43、ielectric where nis the number of helically applied wires; Dis the mean diameter of helically applied wires = the diameter over dielectric + dw; dwis the diameter of helically applied wire; Lis the lay length of helically applied wires. Cable designation (without moisture barrier) Maximum overall di
44、ameter Cable designation (with moisture barrier) Maximum overall diameter of cables with moisture barrier incorporated in the sheath Diameter over dielectric 2 900 1 800 1 300 1 150 1 000 725 550 445 370 295 mm 34.5 23.0 17.5 16.0 14.0 11.0 9.0 7.5 6.5 6.0 2 900 MB 1 800 MB 1 300 MB 1 150 MB 1 000 M
45、B 725 MB 550 MB 445 MB 370 MB 295 MB mm 35.0 24.5 19.0 17.5 16.0 13.5 11.5 10.0 9.0 8.0 mm 29.00 0.30 18.00 0.25 13.00 0.20 11.50 0.20 10.00 0.20 7.25 0.15 5.50 0.15 4.45 0.15 3.70 0.15 2.95 0.10 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) B
46、SI BS 5425-1:1986 4 BSI 06-1999 4.5 Inner conductor diameter The inner conductor diameter shall be adjusted to accommodate the velocity ratio of the particular design so as to comply with the mean characteristic impedance requirements of clause 5. Table 3 Minimum sheath thickness Without moisture ba
47、rrierWith moisture barrier Cable designation Minimum sheath thickness Cable designation Minimum sheath thickness 2 900 1 800 1 300 1 150 1 000 725 550 445 370 295 mm 1.7 1.1 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.5 2 900 MB 1 800 MB 1 300 MB 1 150 MB 1 000 MB 725 MB 550 MB 445 MB 370 MB 295 MB mm 2.0 1.7 1.6
48、 1.6 1.6 1.6 1.6 1.4 1.4 1.4 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 13:09:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5425-1:1986 BSI 06-19995 Section 3. Electrical requirements NOTERecommended methods of testing compliance with the requirements in section 3 are given in Appendi
49、x C but other methods may be adopted by agreement between supplier and purchaser. 5 Mean characteristic impedance (Zm) The mean characteristic impedance shall comply with Table 4. Table 4 Mean characteristic impedance 6 Attenuation The attenuation shall not exceed the values given in Table 5. 7 Uniformity of characteristic impedance NOTEThe characteristic impedance at any frequency is a function of the variations of the local characteristic impedance and also of the spacing of these variations where they are
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