GB/T 4012-20132.6/9.5 mm composite coaxial cable for telecommunication use (English PDF)

1 Scope

The standard lays down the type designations, the sizes, the electrical performance, the delivery length, the acceptance rules, the test methods and the marking and packaging of 2.6/9.5 mm composite coaxial cable for telecommunication use.

It applies to the manufacture, the acceptance and the use of 2.6/9.5 mm composite coaxial cable.

The cable covered by the standard is intended for analogue trunk communication systems of 24 MHz and below, or for digital and analogue wideband information transmission systems such as high speed data, image facsimile and television. The high/low frequency quads and the high frequency twisted pair groups are used in analogue communication systems of 123 kHz and below, and the low frequency quads are used in voice frequency communication systems.

2 Normative references

The documents referred to are GB/T 2952.1 to 2952.3-2008 on outer protective coverings of cables; GB/T 3048.4-2007, GB/T 3048.5-2007 and GB/T 3048.8-2007 on the d.c. resistance of conductors, on insulation resistance and on the a.c. voltage test; GB/T 3953-2009 on round copper wire for electrical purposes; GB/T 4909.2-2009 on dimensional measurement of bare wires; GB/T 5441.2-1985, GB/T 5441.3-1985, GB/T 5441.4-1985, GB/T 5441.6-1985, GB/T 5441.7-1985, GB/T 5441.8-1985 and GB/T 5441.9-1985 on test methods for communication cables, covering working capacitance by the bridge method, capacitance coupling and capacitance unbalance to earth, terminal impedance and internal impedance irregularity of a coaxial pair by the pulse method, crosstalk attenuation by the comparison method, the attenuation constant by the open and short circuit method, the frequency characteristic of the attenuation constant of a coaxial pair by the comparison method, and the ideal screening factor under power frequency conditions; JB/T 8137 (all parts) on cable drums; and YD/T 760-1995 on polyolefin insulating compound for indoor communication cables.

Dated references apply in the dated version only; undated references apply in their latest version, amendments included.

3 Product type designation

3.1 The type designations of the cable are given in Table 1.

3.2 A cable is designated by its type, its size and the number of the standard.

3.3 The example given reads: a composite coaxial cable with an aluminium sheath and a polyethylene jacket containing 4 coaxial pairs, 4 high/low frequency quads, 1 low frequency quad and 4 signal wires is written HOL03 4 x 2.6/9.5 + 4 x 4 x 0.9 (high/low) + 1 x 4 x 0.9 (low) + 4 x 1 x 0.6 (signal) GB/T 4012-2013.

Table 1 lists the type letters with their names and their main uses. HOL is the bare aluminium sheathed composite coaxial cable for fixed laying on land, for aerial, duct and tunnel installation. HOL02 and HOL03 are the aluminium sheathed types with a polyvinyl chloride jacket and with a polyethylene jacket, used as HOL and also suitable for direct burial. HOL22 and HOL23 add steel tape armour and are used as HOL02 and HOL03, for electrified railways and places with strong electrical interference. HOL32 and HOL33 have fine round steel wire armour and are for fixed laying on land, for water crossings. HOQ is the bare lead sheathed type, used as HOL, and HOQ02 and HOQ03 are its jacketed versions. HOQ21, HOQ22 and HOQ23 are lead sheathed with steel tape armour, with a fibrous outer covering or with a polyvinyl chloride or polyethylene jacket. HOQ31, HOQ32, HOQ33, HOQ41, HOQ42 and HOQ43 are lead sheathed with fine or heavy round steel wire armour and the same three outer coverings. A note says that cables with other types of outer covering may be supplied by agreement, and a footnote marks several of the lead sheathed types as products that are not recommended.

4 Sizes

4.1 The sizes of the cable are given in Table 2.

Table 2 sets out the permitted make-up of the cable in five columns: coaxial pairs of 2.6/9.5 mm, high/low frequency quads of 4 x 0.9 mm, high frequency twisted pair groups of 2 x 0.9 mm, low frequency quads of 4 x 0.9 mm and signal wires of 1 x 0.6 mm. A cable with 4 coaxial pairs carries 4 high/low frequency quads, no high frequency twisted pair group, 1 low frequency quad and either no signal wires, 2 or 4 of them. A cable with 8 coaxial pairs carries no high/low frequency quad, 7 low frequency quads, and its high frequency twisted pair groups and signal wires are combined in three ways, which the scan shows as no group with no signal wire or with 2 or 4 signal wires, 4 groups, and 8 groups with 6 signal wires; the pairing of the rows in the last two columns of this table could not be established with certainty and the combinations are therefore not restated as a list. A footnote states that the green and blue insulated cores are the high frequency working pair and the white and red insulated cores the low frequency working pair.

5 Coaxial pair

5.1 The inner conductor is a round copper wire of nominal diameter 2.6 mm and shall meet GB/T 3953-2009.

5.2 The insulation is of foamed or foam skin polyolefin and shall meet YD/T 760-1995.

5.3 The outer conductor is formed by longitudinally applying a soft copper tape of nominal thickness 0.25 mm. The nominal diameter of the outer conductor is 9.5 mm.

5.4 Two tinned steel tapes of nominal thickness 0.15 mm and two layers of insulating paper tape shall be applied over the outer conductor with a gap.

5.5 The performance of the coaxial pair shall meet Table 3.

Table 3 fixes four items. The d.c. resistance of the inner conductor at 20 °C is not greater than 3.5 ohm/km, converted with the factor l/1000. The terminal impedance at 2.5 MHz has a nominal value of 75 ohm, and the table sets deviation limits and limits on the difference between the impedances of the A and B ends, each quoted against a percentage figure. The impedance irregularity is limited in parts per thousand, with the equivalent value in decibels given in brackets, again against a percentage figure. The attenuation constant at 13 °C is not greater than 1.32 dB/km at 0.3 MHz, 2.37 dB/km at 1 MHz, 3.74 dB/km at 2.5 MHz, 4.73 dB/km at 4 MHz, 7.09 dB/km at 9 MHz, 8.19 dB/km at 12 MHz and 10.59 dB/km at 20 MHz, and is 11.60 +/- 0.10 dB/km at 24 MHz. The footnotes state that the terminal impedance is calculated at both ends of the coaxial pair, that the impedance irregularity is calculated from the larger of the values measured at the two ends and that steel wire armoured cables are allowed a lower figure, and that the maximum nominal value of the attenuation constant is the average of a full band test on 20 single coaxial pairs of about 3 km taken at random from not less than 60 km of cable.

6 High/low frequency quad

6.1 The conducting core is a soft copper wire of nominal diameter 0.9 mm and shall meet GB/T 3953-2009.

6.2 The insulation is of foamed polyethylene and shall meet YD/T 760-1995.

6.3 Four insulated cores coloured red, green, white and blue are stranded into a quad; the colour arrangement at the A end is shown in Figure 1. The white and red cores form the low frequency working pair and the green and blue cores the high frequency working pair. The lay length shall be not greater than 300 mm, all the high/low frequency quads in one cable shall have different lay lengths, and cotton yarn, plastic yarn or tape of different colours shall be spirally lapped over them with a gap.

6.4 The electrical performance of the high/low frequency quad shall meet Table 4.

Table 4 fixes the d.c. resistance of each conducting core at 20 °C as not greater than 28.5 ohm/km, converted with the factor l/1000; the ratio of the d.c. resistance difference of a working pair to the loop resistance as not greater than 1.0 %; the average working capacitance at 0.8 kHz as 29.5 +/- 2.2 nF/km, converted with the factor l/1000; and the attenuation constant at 13 °C and 123 kHz as not greater than 3.4 dB/km.

7 High frequency twisted pair group

7.1 The conducting core is a soft copper wire of nominal diameter 0.9 mm and shall meet GB/T 3953-2009.

7.2 The insulation is of foamed polyethylene or of foamed polyolefin and shall meet YD/T 760-1995.

7.3 Two insulated cores of different colours are stranded into a twisted pair group; the lay length shall be not greater than 150 mm and all the high frequency twisted pair groups in one cable shall have different lay lengths.

7.4 The electrical performance of the high frequency twisted pair group shall meet Table 5.

Table 5 fixes the same four items as Table 4, with the d.c. resistance of each conducting core at 20 °C not greater than 28.5 ohm/km, the ratio of the d.c. resistance difference of a working pair to the loop resistance not greater than 1.0 %, the average working capacitance at 0.8 kHz equal to 34 +/- 2.5 nF/km and the attenuation constant at 13 °C and 123 kHz not greater than 3.4 dB/km.

8 Low frequency quad

8.1 The conducting core is a soft copper wire of nominal diameter 0.9 mm and shall meet GB/T 3953-2009.

8.2 The insulation is of foamed polyethylene or of foamed polyolefin and shall meet YD/T 760-1995.

8.3 Four insulated cores coloured red, green, white and blue are stranded into a quad; the colour arrangement at the A end is shown in Figure 1. The white and red cores form the low frequency working pair and the green and blue cores the high frequency working pair. The lay length shall be not greater than 300 mm, all the high/low frequency quads in one cable shall have different lay lengths, and cotton yarn, plastic yarn or tape of different colours shall be spirally lapped over them with a gap.

8.4 The electrical performance of the low frequency quad shall meet Table 6.

Table 6 fixes the d.c. resistance of each conducting core at 20 °C as not greater than 28.5 ohm/km, the ratio of the d.c. resistance difference of a working pair to the loop resistance as not greater than 1.0 %, and the working capacitance at 0.8 kHz as not greater than 32 nF/km in a four coaxial pair cable and not greater than 26 nF/km in an eight coaxial pair cable.

9 Signal wire

9.1 The conducting core is a soft copper wire of nominal diameter 0.6 mm and shall meet GB/T 3953-2009.

9.2 The insulation is of solid polyethylene and shall meet YD/T 760-1995; its colour shall follow Table 7.

9.3 The d.c. resistance of the conducting core at 20 °C shall be not greater than 65.8 ohm/km.

9.4 Before the core is assembled, the measured terminal impedance at the drum end of the coaxial pair shall be matched within a range of 0.2 ohm when the drums are made up.

Table 7 gives the insulation colours of the signal wires against the number of coaxial pairs and the number of signal wires. The wire order runs from 1 to 6 and the colours printed against it are, in order, red, green, white, blue, white and blue. The table then marks with tick marks which wire orders are used when a four coaxial pair cable carries 2 or 4 signal wires and when an eight coaxial pair cable carries 2, 4 or 6 of them; the tick marks could not be attributed to the columns with certainty on the scan and the combinations are therefore not restated here.

10 Cable core

10.1 The cable core is stranded concentrically, the outer layer to the right. The lay length of the coaxial pairs in the core shall be not greater than 800 mm in a four coaxial pair cable and not greater than 1 050 mm in an eight coaxial pair cable. In an eight coaxial pair core, insulating paper tape shall be lapped between the inner and the outer layer.

10.2 The colour arrangement of the cable core at the A end is shown in Figure 2. In each layer, the group or pair with red, or white and red, is taken as the first group and the one with green, or white and green, as the second group; the wire order is counted clockwise. When the core has no high frequency twisted pair group, coaxial pairs I and II shall follow the wire order with the colours red and green. When there are 4 high frequency twisted pair groups, they shall be groups 1, 2, 5 and 6, as shown in Figure 2.

10.3 Not less than 5 layers of K-17 paper tape, or other cable paper tape of the same total thickness, shall be lapped over the core with a gap. A measuring tape shall be laid along the whole length of the core, and the name of the manufacturer and the year of manufacture shall be printed on the outermost paper tape or on the measuring tape.

Figure 2 shows the two arrangements at the A end. In the four coaxial pair cable it shows 4 coaxial pairs of 2.6/9.5, 4 high/low frequency quads of 4 x 0.9, 1 low frequency quad of 4 x 0.9 with a binder yarn of any colour, and 4 signal wires of 1 x 0.6. In the eight coaxial pair cable it shows 8 coaxial pairs of 2.6/9.5, 8 high frequency twisted pair groups of 2 x 0.9, 7 low frequency quads of 4 x 0.9, 6 signal wires of 1 x 0.6 and the insulating paper tape.

11 Metallic sheath

11.1 The purity of the aluminium used for the aluminium sheath shall be not lower than 99.6 %. The lead alloy used for the lead sheath shall contain 0.4 % to 0.8 % of antimony and not more than 0.08 % of copper.

11.2 The thickness of the aluminium sheath shall meet Table 8 and the thickness of the lead sheath shall meet Table 9.

11.3 The metallic sheath shall be sealed and free from gas leakage.

11.4 A lead sheath of inner diameter above 15 mm shall withstand the expansion test.

Table 8 gives the minimum thickness of the aluminium sheath in millimetres against the calculated diameter under the sheath, in three columns: plain aluminium sheath, corrugated aluminium sheath where the screening factor does not matter, and corrugated aluminium sheath with a screening requirement equal to that of the plain sheath. The diameter classes run from 20.00 mm and below to 70.00 mm and above. For the plain sheath the values run from 1.30 mm in the smallest class to 1.90 mm in the class 45.01 mm to 50.00 mm, above which the column is not filled; the corrugated sheath columns are not filled below 35.01 mm and run up to 1.80 mm and 2.10 mm in the largest class.

Table 9 gives the thickness of the lead sheath in millimetres against the calculated diameter under the sheath, from 13.00 mm and below to the class 46.01 mm to 50.00 mm, with a minimum value and a nominal value for three groups of types: HOQ; HOQ02, HOQ03, HOQ21, HOQ22 and HOQ23; and HOQ31, HOQ41, HOQ32, HOQ33, HOQ42 and HOQ43. In the smallest class the minimum and nominal values are 1.20 mm and 1.40 mm for the first group, 1.10 mm and 1.25 mm for the second and 1.80 mm and 2.05 mm for the third; in the largest class they are 2.30 mm and 2.60 mm, 2.00 mm and 2.30 mm, and 2.50 mm and 2.80 mm.

12 Outer protective covering

12.1 The outer protective covering of the cable shall meet the requirements of GB/T 2952-2008.