The History of Cable TV

Cable TV was the original improved solution to the distance, obstacles and quality issues that were challenges for over-the-air broadcast TV reception.  The original solution was quite simple; use better reception antennas and an extension cord.  The optimum setup for a homeowner to receive over-the-air broadcast, was to use an elevated antenna (rooftop or tower), and connect the cable from the antenna to their TV.  Early cable systems used that same methodology to provide the first cable TV implementation.  They erected large powerful antenna on mountain and hill tops, or other elevated places and just extended the cable to households.

Cable TV providers would assemble all of the programming they could receive with their antennas, package it, amplify it, and send it down the line to households.  For the average household that subscribed to this new service this was a bonanza.  They got a better, clearer picture and a greater number of channels courtesy of the cable TV company’s superior antennas.  As use of the new service grew, cable TV companies would just add splitters and additional amplifiers so they could extend their service area coverage.  The cable system topology resembled a tree, with branches and limbs that stretched into the surrounding communities.

The Problem for cable TV companies

The improved picture the cable system provided saw rapid adoption and expansion, and re-introduced similar types of problems as those experienced by over-the-air television systems.  With over-the-air broadcast, distance and obstacles cause the picture quality to deteriorate.  The problem for cable TV providers was the cable (the wire) itself.  Wire has physical limits to how far it can transmit a signal; the signal degrades as the length of the wire increases.  The other problem is that multiple households must be served at the same time, so the signal must be split to be able to do this.  The splitters add a further obstacle to the signal strength, further degrading the signal quality.  To combat this problem amplifiers are added to boost the signal, but the amplifier being an electronic device introduces noise and amplifies not only the signal but the noise too.  Every successive splitter and amplifier introduces noise into the signal path, so the quality of the signal continues to degrade.  Eventually the amplified noise gets so great that it drowns out the signal.  So if your house was close enough to the cable TV providers’ antenna, the signal you received may only be split 2 or 3 times and your picture was great.  If you were further out and the signal you received had been split and amplified 30 times, then your picture was not so good.

Victims of their own success, cable TV companies were now faced with the challenge of ensuring that subscribers at the furthest reaches of their network got the same great quality picture as those closer to the distribution point.  To solve this problem, cable TV providers began to use fiber-optic cable in their network.  The physical properties of fiber-optic cable allow it to carry a signal a far greater distance than coaxial cable; up to 70 KM, before the signal needs to be re-amplified.  Fiber optic cable transmits light, so it doesn’t suffer the same kind of noise induction that coaxial does when it is amplified to extend the length of the cable run.  Modern cable systems networks are now a hybrid fiber-coaxial (HFC) mix.  Fiber-optic cable forms the long haul section of the networks; the signal goes back to coaxial cable at what is called the fiber node, which is located where the network enters your subdivision or at the top of your street.  The coaxial portion of the signal is split a lot fewer times, before it reaches your house.