What is an Analog TV Signal?

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  • Written By: R. Kayne
  • Edited By: O. Wallace
  • Last Modified Date: 05 February 2016
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An analog TV signal is made up of a video signal broadcast on AM radio waves, and an audio signal broadcast on FM waves. Analog technology is currently being replaced by digital technology throughout the world.

In the U.S., black-and-white analog TV transmissions were standardized in 1941 by the National Television System Committee (NTSC), later followed by an updated color standard in 1953. NTSC was adopted by North America, Central America, parts of South America, Japan and other nations. Other parts of the world developed Phase Altering Line (PAL) and Sèquentiel Couleur Avec Mèmoire (SECAM) analog standards. Less popular standards were also developed.

Analog broadcasts have an aspect ratio of 4:3, or nearly square in configuration. An NTSC signal has 525 scan lines, though only 486 make up the visible raster. The remaining lines carry synchronization and vertical retrace information. The lines are painted in two passes across an analog screen, each pass painting every other line, interlacing the passes to create a flicker-free image. Frame rate is 30-frames per second, resulting in an actual frame rate of 29.97 frames per second.


A PAL analog TV signal comes in many flavors, including B/G/H/I/D/M and PAL Nc. Most consist of 625 scan lines, interlaced, at 25 frames per second, though audio carrier frequencies differ between standards. PAL M, like NTCS, uses 525 scan lines and 29.97 frames per second. Brazil uses PAL M, while other flavors of PAL are used in most of South America, Australia, China and other territories, noting again that digital broadcasting is replacing this technology at various rates, regionally.

The SECAM standard was developed in France and has also evolved over the years into different flavors. It also uses 625 scan lines, except for its M version, which like PAL M and NTSC has 525 scan lines. SECAM was used in France, Africa, Russia and other parts of the world, though many territories migrated to PAL throughout the 1990s.

An analog TV signal is subject to interference that can cause undesired effects like ghosting and snow. Distance from the transmitter and intervening topography factor into signal clarity.

An analog television is quite heavy for its size due to the lead-encased, vacuumed chamber that houses the scanning mechanism known as a cathode ray tube (CRT). This mechanism converts the broadcast signal into a moving picture by shooting electrons against the back of the phosphorous television screen many times per second to re-create each frame of information. The analog TV has a deep footprint, taking up a large amount of space, and emits off a fair amount of radiation compared to digital TVs.

Analog TV broadcasting is legacy technology, though it continues to be used in territories that have not yet switched to digital standards. Digital technologies use less bandwidth to deliver more information on the signal, resulting in the ability for higher resolutions, non-interlaced signals, and a 16:9 aspect ratio (resembling a movie screen in configuration). Other advantages of digital TV include the ability to broadcast at lower resolutions that are still higher than analog TV, creating room for multiple channel broadcasting within the same allotted frequency band.


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Post 6

@wavy58 – I remember that, too! I was big on video games, and I always had to shut off my TV if I needed to pause the game for any length of time.

I was disappointed when I got a digital flat screen TV and found out that I couldn't play my old video games on it. I don't even think I could hook it up. My husband tried and told me it wouldn't work.

Luckily, I still had my old analog TV in the bedroom. I was able to play my games on this TV.

It would really be nice to play it on the big screen in the living room, though. Does anyone know if there is a way to hook up an old classic video game system to a new digital TV?

Post 5

There is a big difference in quality between analog TV screens and digital ones. If you are used to watching HD TV, the difference is even more pronounced.

With analog TVs, sometimes the reception is full of snow. At times, it can get so bad that you really can't see what's going on. Of course, it isn't this way all the time, but it does happen.

With digital TV, the images are beautifully clear. You can even see freckles and wrinkles on actresses that you could never see with an analog TV.

Post 4

Many people were upset when the local television stations decided to switch to digital broadcasting. I live in a low income area, and most people here could not afford digital televisions at the time.

So, they had the option of getting a digital to analog TV signal converter. The government offered coupons to people who wanted to buy a converter box but couldn't afford one, and the coupons would pay most if not all of the cost.

I see why people need to keep their local channels. Whenever there is severe weather, they need to know when to take shelter. Also, if there is an escaped murder on the loose or some other sort of danger, people need

access to that information.

The converter boxes allowed people who couldn't afford the $700+ commitment to a new digital TV the opportunity to keep watching their local news and other programs. I think it was a great thing that our government offered the coupons.

Post 3

I grew up back in the days of the analog television signal, and my parents always cautioned me not to leave something paused on the screen for a long time. I played video games all the time, and my dad always told me that if I paused one in order to come eat dinner, I should turn the television off and leave only the video console on.

He said that images could get burned permanently onto the screen if left there for very long. This was also the reason he told me not to pause anything I might be watching on my VCR and go away for more than a couple of minutes.

Post 2

I never knew that analog TV signals threw off more radiation than digital signals! I wonder if this additional background radiation is one of the reasons they are switching to the digital format.

I read that the digital signal format lessons eyestrain, and that is why they targeted the larger TV sets to go digital first. It really is interesting to look at more of the underlying factors that are influencing the change from analog TV signals to digital ones.

Post 1

With most nations switching to a standard digital format for television broadcasting it really seems that the analog TV signal is done for.

With the changes being made to how we get our television signals, those who are still relying on free TV signals that you can pick up with a simple antenna are going to be out of luck.

At the very least, you are going to need to get a digital TV decoder to be able to watch your shows. For many without this technology, you'll find your screens going black as the changes are made.

Does anyone feel that this change is good step to make sure everyone has a higher quality TV experience, or just another cash grab?

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