How HDTV WorksThe switch to digital television broadcast transmissions has opened up a whole new world of options for the avid TV consumer. HDTV, or high-definition television, is one of several types of broadcast signals used by broadcasters across the United States. Understanding how HDTV works can help in determining what type of television equipment will best transmit a local area’s signal.

Analog vs. Digital Broadcasts

Before the advent of digital signals, televisions received sound and video information via radio waves, or analog signals. The change to digital involved transmitting sound and video using ones and zeroes or digital bits across radio waves. The switch from wave-form transmissions to digital bits means broadcast signals can carry more information. More information allows for more detail, which accounts for the improved picture and sound quality found in digital versus analog transmissions.

DTV Signals

Digital television signals can transmit sound and video information in different formats, which accounts for differences in quality. In total, there are 18 digital broadcast formats used to transmit video or images across a television screen. These formats vary in picture size, picture detail and speed of transmission. An HDTV signal is the highest quality signal available.

Picture size –also known as aspect ratio- has to do with the length and width of the image being transmitted. HDTV delivers a 16:9 aspect ratio compared to analog’s standard 4:3 aspect ratio. Picture detail, or resolution has to do with the number of pixels, or information bits contained in each picture. HDTV resolutions allow for 1920 x 1080 pixels, while analog averages up to 704 x 480 pixels. Speed of transmission, or frame rate determines how fast complete images are transmitted across a TV screen. DTV transmission rates can range anywhere from 24 to 60 frames per second, while analog signal information can only transmit partial image renderings per frame rate.

Equipment Compatibility

Broadcast companies determine the type of digital signal they transmit, so different areas or regions may receive different quality signals. On the flip side, electronics manufacturers design televisions and equipment according to their own specifications. This means aspect ratios and picture resolutions can vary from television to television.

So the only way a person can view high definition television is if -

  • a particular channel uses an HDTV signal
  • there’s a way to receive the signal, such as through a cable or satellite service
  • the television set is capable of rendering an HDTV signal

Types of Televisions

A traditional analog-based television cannot transmit a digital signal without an antenna and receiver, or descrambler unit. In effect, analog-based televisions can’t transmit the mass of information contained in an HDTV signal at all. In order to see and hear all the information an HDTV signal delivers, a television has to have built-in HDTV capabilities.

Integrated HDTV sets come with a digital tuner. If a local broadcast station uses an HDTV signal, a person can view high-definition television on an integrated set provided they hook an antenna up to the TV. Another type of television –known as an HDTV ready set- requires a receiver service, such as a cable or satellite hook-up.

Ultimately, HDTV televisions that provide the same aspect ratio and screen resolution specifications as the incoming signal will deliver the best picture and sound qualities.

Paul is writing for Quatrix Antennas, a Sydney based TV antenna installation company, specialising in digital antenna installations.