440
COMMUNITY ANTENNA TELEVISION (CABLE TELEVISION)
Figure 17.5
Attenuation-frequency response for 7/8-in. coaxial cable, Z
o
= 75 , Andrew HJ series
helix. (Courtesy of Andrew Corp.)
1
2
-in. coaxial cable. Such a length of cable would have 5.45-dB loss at 54 MHz and 13-dB
loss at 300 MHz. The equalizer would probably present a loss of 0.5 dB at 300 MHz and
8.1 dB at 54 MHz.
17.3.8
Taps
A tap is similar to a directional coupler. It is a device inserted into a coaxial cable, which
diverts a predetermined amount of its RF energy to one or more tap outputs for the purpose
of feeding a TV signal into subscriber drop cables. The remaining balance of the signal
energy is passed on down the distribution system to the next tap or distribution amplifier.
The concept of the tap and its related distribution system is shown in Figure 17.6.
Figure 17.6
A simplified layout of a CATV system showing its basic elements. The objective is to provide
a
+10.5-dBmV signal level at the drops (tap outputs). LEA, line extender amplifier.
Summary :
It is a device inserted into a coaxial cable, which diverts a predetermined amount of its RF energy to one or more tap outputs for the purpose of feeding a TV signal into subscriber drop cables.
Tags :
tap,cable,mhz,system,figure,distribution,coaxial,signal,loss,teleision,176,energy,300