RG-6A/U And RG-114A/U Coaxial Cables

For comparison, these cables show the following attenuation characteristics*:

RG-6A/U: Down approximately 3 dB for 100 feet at a frequency of 100 Mc/sec.

RG-114A/U: Down approximately 3 dB for 100 feet at a frequency of 100 Mc/sec.

5.2.4 The Effect of Temperature on Pulse-Height Attenuation and D-C Resistance

A variety of cables were tested for pulse-height attenuation at several temperatures. A description of the cables is given in Table 5-2, and the results of the tests are shown in Figure 5-5.

The main contributor to variation of attenuation with temperature is variation of the resistivity, д of the conductor. A plot of measured resistance of several materials, normalized to 20 mils diameter by 100 feet long, versus temperature is given in Figure 5-6.

Note that the theoretical data do not include calculations for the cables using nickel or nickel clad copper as conductors, because the attenuation equations are not valid for cables having conductors with magnetic properties.

image472 image473 Подпись: (5-9)
image475

Note, also, that the above procedure is valid only for cables in which the attenuation at f = 1/(2T) is not much greater than that at low frequencies. If these two attenuations are significantly different, the shape of the pulse changes in traveling along the cable and the method of calculating output pulse height would be more involved than the approximate method outlined above. The ratio of high-frequency to low-frequency attenuations is given by

where p is in ohm-meters and a, b, and x are in feet.

♦Catalog W2, American Phenolic Corporation.

TABLE 5-2

CABLE DESCRIPTION

Cable

Insulation

Center

Conductor o. d.

Guard o. d.

. Shield o. d.

Length (ft)

Capacitance • (Pf/ft)

Characteristic

Impedance

Copper

Quartz Fiber

7 — 5-mil strands

75 mils

110 mils

103

36.5

56 fl

Nickel Clad Copper

Quartz Fiber.

20 mils

95 mils

135 mils

100

26. 7

. 82 a

Stainless

Steel

Alumina.

17 mils

62 mils

125 mils

30

124

36 n

Molybdenum

Quartz Fiber

20 mils

95 mils

135 mils

102

32.2

56 П

Nickel

Quartz Fiber

10 mils

95 mils

135 mils

32. 25

22.6

Stainless

Steel

Quartz Fiber

20 mils

95 mils

135 mils

100

27

75 Л

Подпись: GEAP-4900СЛ. —————————- .

1 ‘

~ NOTE: Quartz fiber insulated cables have braided guards and shields of 4-mil wire.

image477

Подпись: RESISTANCE (ohros/100 ft)

0 TOO 200 300 400 500 600 700 800

TEMPERATURE (°F) ‘

 

image479

Figure 5-6. D-C Resistance Variation With Temperature — Normalized to 20 Mils Diameter

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