Understanding the Difference Between NTSC, ATSC and QAM?
Some of the technical language can seem difficult when you are looking to buy a TV tuner, or a TV.
You will likely read, or hear terms like ATSC, NTSC, and QAM being used and it is important to understand what each term means and what the difference is between each of them.
Luckily, it is not too difficult to understand the terms when they are broken down into simple language. I have written out some straightforward explanations below.
Before I define each of the terms, however, it is important to understand that TV signals are usually received in one of two ways, either by aerial, or cable, and that:
- The terms NTSC and ATSC relate to TV signals that are received over the air (often abbreviated to OTA.) using an aerial. An old analog aerial will pick up NTSC signals, but you will need a newer, digital aerial to pick up ATSC signals
- QAM, on the other hand, relates to TV signals that are received via cable.
What is NTSC?
NTSC is generally used to refer to the old analog signal which was first adopted in the USA in the 1940s. It has largely been phased out in favor of digital ATSC broadcasting, however.
NTSC is inferior to ATSC, as it is doesn’t deliver HDTV picture quality, or the widescreen format. Audio audio quality is also inferior.
NTSC stands for the National Television System Committee, which were the group who introduced the original standards for analog TV transmission in the USA back back in the early 1940s.
This was done to resolve differences between the various TV companies and standardize the system. The system was updated in 1953 to accommodate the change from black and white to color television.
As well as the USA and Canada, the NTSC system was or is used in Central America, the Caribbean, parts of South America, and in several Asian countries, including Japan.
High-power OTA NTSC broadcasting was switched off in 2009 in the USA, and in 2011 it was discontinued in Canada and most of the other countries.
NTSC vs ATSC
What is ATSC?
ATSC is the OTA digital signal used in the USA. It is superior to the old NTSC analog system, which it is designed to replace, because it can deliver HDTV picture quality in a wide screen format, as well as being capable of providing theater quality audio.
To use an analog TV with ATSC you need a converter, however, to cope with a digital signal. The Federal Communication Commission (FCC) require that all new TVs have built-in ATSC tuners.
ATSC stands for the Advanced Television Systems Committee, which was the group who replaced the NTSC in the USA in 1982. As part of the transition process, a consortium of electronics and telecommunications companies, known as the Grand Alliance worked in the early 1990s to put together the standards for what would come to be known as HDTV.
What is QAM?
QAM is essentially the cable version of ATSC, with QAM tuners allowing your TV to receive unencrypted digital signals from a cable provider (a cable box is required for the encrypted ones).
This means that you generally will get free, usually local cable channels with a QAM tuner, but you will need a cable box or cablecard to get the channels that are provided by the cable television providers.
Difference Between NTSC and PAL
PAL stands for "Phase Alternating Line" and is a colour encoding system for analog TV used by many countries instead of NTSC. It was developed in Germany and originally adopted by Western Europe.
The first countries to broadcast TV using PAL were West Germany and the United Kingdom in 1967.
The other main analog color TV system used across the world, besides NTSC and PAL, is SECAM (which stands for Séquentiel couleur à mémoire, French for "Sequential Color with Memory"). SECAM was the the first European color television standard.
NTSC is or was generally used in North and Central America. SECAM is or was used in France, East Africa, Russia, and some Asian countries. PAL is or was used in Western Europe, most of Arica, the Middle East, most of South America, Southeast Asia, and Australasia.
Many countries have now phased out analog TV altogether, however, with the introduction of digital technology.
I think it's brought the world a lot closer together, and will continue to do that. There are downsides to everything; there are unintended consequences to everything. The most corrosive piece of technology that I've ever seen is called television - but then, again, television, at its best, is magnificent.— Steve Jobs
Questions & Answers
Can a US TV with ATSC/NTSC/QAM work in an African country using PAL?
You don't specify a country in Africa. DVB-T (Digital Video Broadcast – Terrestrial) is the now the most common system used in Africa. Set-top boxes used by South Africa-based DSTV or Multi-Choice TV in a number of sub-Saharan African countries are based on this standard. Your TV will have to be compatible with the set-top boxes in use for it to work properly. Most (but not all) HDTV systems that are compliant with the ATSC standard are also compliant with the DVB-T standard. I advise that you ask your provider in Africa for specific advice before buying a TV in the USA.
© 2012 Paul Goodman