How Cable TV Works – A Basic Cable Package

So you’re sitting in front of the TV, watching your favorite show. You’re probably not giving much thought to exactly how this program got to you, or where it came from. If it happens to be a live broadcast, then you’ll know its original location, but do you know how it’s actually sent to you? TV viewing is something most of us take for granted. But when you understand exactly how cable TV works, then you’ll probably appreciate it more. So we’re going to give you a simple explanation here. And when you can’t find anything you like on the 150 or so channels you have, then maybe you’ll want to brush up on your education and check this out.

How did cable TV come about?

In the beginning, there was television. It was all live – the technology for recording programs hadn’t been invented yet. Basically, a camera caught the action and transmitted it via an electric current to a TV set, where the antenna converted the electrical pulses back into the original images and sound. That’s the simplest form of a TV signal.

These signals were actually transmitted over radio frequencies, which travel in straight lines. So, if your TV wasn’t in the “line of sight” of the source, the signal was blocked, and your TV screen would be blank. As a result, the only people who had TV’s in those days (back in the 1950s), were those who lived on higher ground, or were close to the source of the program.

However, there was an exception to this: People who lived in the valleys of Pennsylvania came up with a creative solution to their viewing woes. By putting up antennas on the high spots, the tallest hills, around them, and then running cables down to their homes, they could receive the signals clearly. This idea of sending signals over cables, rather than using airwaves, was the first beginnings of what we know today as cable TV.

Cable systems needed miles of cables

As Pennsylvania’s cable idea became recognized as a solution to the broadcast challenges of the day, cable TV technology emerged. The first challenge they had to overcome was that the original system worked well, but only within short distances. Signals sent through cables were subject to interference. Also, the longer the cable, and the farther the signal had to travel, the weaker it became and, by the time it reached the TV set, it was pretty distorted.

So, to solve the distance problem, a series of amplifiers were installed along the way – about one every 1000 feet, thus increasing the strength of the signal. But the problem with this system was that every time the signal passed through an amplifier, it would pick up interference in the form of distortion and noise. And, if there was a breakdown in any of the amplifiers, there’d be no signal at all.

Other methods of transmitting signals are explored

The amplifier problems led cable TV engineers to research the transmitting of signals via microwaves. Signals were captured by receiving towers, located high enough to prevent being blocked. This greatly increased viewership in the U.S., opening up the possibilities of multiple-channel broadcasting from the TV networks. And of course, the more channels broadcasted, the more the networks would earn. So this forward movement in technology was indeed welcome.

With the same goal of increasing available TV programming, small communities started to copy the cable idea. Community cable companies were formed, with the purpose of importing as many TV stations as they could for their viewers. This marked the beginning of CATV, or community antenna television.

Understanding the airwaves

It’s important here to understand the technology behind signal transmissions over the airwaves, as well as through cables. This technology is the same for cable as it is for the airways. The total amount of all airwaves is known as the spectrum. The spectrum is separated into frequencies. To understand what these are, think of the air being split into thousands of individual strips – these are the frequencies. Each frequency can carry a signal, which is sent in the form of an electric current. The TV signal at the source, or the origin, is converted from images and sound to an electric current, sent over the airwaves to be received by a TV antenna, which converts it back into the original images and sound.

Frequencies are given values, the smallest of which is 1 hertz (Hz). In the U.S., the FCC (Federal Communications Commission) allocates certain frequencies for signals, usually in blocks. For example, a TV station is given the frequency of 6 MHz (megahertz). Remember the old VHF channels on your TV – channels 1-12? VHF stands for very high frequency, and that was what the FCC had designated for those stations.

And that other dial on your TV – the UHF dial – what was that? Well, UHF stands for ultra high frequency, which the FCC had designated to channels 14-69. The signals for these channels were sent between the frequencies of 470 MHz-812 MHz. You might also remember your TV having a CATV/Antenna switch. That would tell your TV which frequency to receive your signal from and, therefore, which channel you’d see on your screen.

The interference challenges haven’t been met

But with the creation of cable TV, an old challenge resurfaced – interference. And the interference was coming from the original microwave signal of the same program. The first solution to this problem was handled by splitting the VHF signals into 2 blocks, thus preventing interference from radio stations.

As cable TV progressed, methods of preventing interference improved. Have you noticed that channels 1-6 aren’t actually carried on channels 1-6? That’s because, if they were, you could receive one signal over the airwaves, and one signal through the cable, for the same program. Since these signals travel at slightly different speeds, they’d arrive on your screen at almost the same time, but not quite. The result of this would be a double image, known as “ghosting”. So that’s why you’ll find your cable channel number to be different from the actual station number.

Satellites create opportunities for channel expansion

With the outset of satellites for communication, a whole new opportunity presented itself to the cable TV industry. Now they could import programs from broadcasters across the country, package them up, and retransmit them to your home – all via satellite.

Another advantage of satellite broadcasting was the increased bandwidth now available. Bandwidth refers to the rate that information can be sent through a channel – the greater the bandwidth, the more information that can be sent in a given amount of time. Remember the first cable TV systems? They could only transmit 33 channels because they only used frequencies up to 200 MHz. But with improved technology, bandwidths were gradually increased to 300, 400, 500 and now, even 550 MHz. The result of this, is that you can now receive 91 channels on your TV.

Technology continued to improve

In the continued quest to cut down on interference and produce a clearer picture, improved cable technology was developed. Cable providers were importing their programming, assigning it to various channels, and re-transmitting it to their customers. The introduction of fiber-optic cable allowed them to provide this service with much-improved quality. One of the big advantages to fiber-optic cable was that it wasn’t subject to the interference challenges of the earlier coaxial cable. That meant that they didn’t need as many amplifiers on the line, either. So the bottom line was that the signal they sent to homes was much higher in quality.

Fiber-optic cable also allowed cable providers to be more selective with their programming. Since just one of these cables could serve as many as 500 homes, providers could target individual communities for messages and services. This eventually led to the creation of LANs (local-area networks) which, in turn presented the opportunity for them to provide Internet access through modems.

Always seeking ways to increase bandwidth capacity, cable TV technologists discovered MPEG compression, which converts signals from analog to digital. By doing this, they could transmit up to 10 channels of video in a 6 MHz bandwidth. With the overall 550-MHz bandwidth, and 10 channels broadcast within 6 MHz…well, you do the math – almost 1000 channels – and in HD (high-definition) TV quality.

Cable TV today

Wow – 1000 channels! Bruce Springsteen once recorded a song called “57 Channels and Nothing on”. But with 1000 channels, do you think you could find at least something to watch? Probably. And, as you watch, perhaps you’ll think, in the back of your mind, how that signal gets to you. Because now you know how cable TV works. And, with all those channels, your “basic cable package” will most likely be, a thing of the past!

About The Author

Gareth Marples is a business writer providing valuable tips and advice for consumers purchasing home theater systems, Dish Network subscriptions and digital video recorders. His numerous articles offer moneysaving tips and valuable insight on typically confusing topics.

This article on "How Cable TV Works – A Basic Cable Package" reprinted with permission.