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OTA DTv Over-the-Air Digital Television (OTA DTv)

PAGE CONTENTS -- Broadcast | Channels | DTv's - HDTV - Signal Level | Reception
TV Broadcast Tower

DIGITAL COMPARED TO ANALOG BROADCAST
Over-the-Air (OTA) digital television (DTv) requires a stronger signal than analog TV. Additionally, most DTv broadcast are in the UHF frequency band instead of the VHF band. UHF signals are higher in frequency and do not pass through or around objects as well as VHF signals. Also, over-the-air transmission and cable losses are greater at UHF frequencies. Antennas that picked up analog TV signals will also pick up digital TV signals, if the signal is strong enough.

  • Digital TV Requires a Stronger Signal.
  • Most Digital Stations are in the UHF Band.
    • Elevated terrain (Masking) blocks UHF signals.
    • UHF dose not go through walls, roofs or objects as well.
    • UHF does not bend around large structures as well.
  • Analog antennas will pick up digital signals.

A digital television's picture and sound quality are either 100%, or nothing. There are rare instances the signal power is just strong enough to decode, but fades in and out enough to pixelate the picture and/or garble the sound. This situation changes with atmospheric conditions and only last seconds to hours, then the signal is either good or gone. Analog TV processed weaker signals, the weaker the signal the more noise (snow) in the picture.

Digital TV broadcast are in high or standard definition (see Digital Televisions below). Cable and satellite operators often compress local broadcast channels before re-broadcasting. The compression reduces picture quality compared to over-the-air broadcast. Compressing signals opens up more bandwidth and allows providers to squeeze in more channels nobody watches.

Analog TV broadcast in the United States ended June 12th (Friday), 2009. Since the introduction of digital TV, the number of over-the-air network channels has dramatically increased.


TV and RF channels

DIGITAL AND ANALOG CHANNELS
The old analog TV channels were the same as their broadcast Radio Frequency (RF) channel, one network per channel. Digital TV can broadcast multiple channels (in 1 RF channel) and uses 2 types of channels, the TV channel (also called Virtual channel) displayed on the TV, and the broadcast RF channel. A stations's TV channel may or may not be the same as it's RF channel. Most analog stations changed their RF channel (and most VHF stations moved to UHF) for DTv, but were allowed to keep their old analog channel identification as their TV or Virtual channel. Stations that signed-on the air after the transition to digital usually have the same TV and RF channel.

Analog Channel Digital Channel
TV = RF
channel
  • TV (Virtual) channel,
    - displayed on television.
    - multiple sub-channels.
  • RF broadcast channel.
    VHF or UHF frequency band.

Sub-channels
Digital Channel numbers are the virtual TV channel, then a dot or dash, then sub-channel number (e.g. 6.3 or 6-3). Television channel 6.3 is virtual TV channel 6, sub-channel 3. The number of sub-channels varies from 1 to 7 or more.

Station Callsign, Power and Service Class (Show more / Hide...)


HDTv Set

DIGITAL TELEVISION
Almost all television's manufactured since 2007 have a built-in digital tuner, or more specifically an ATSC tuner, for receiving over-the-air TV. Some digital televisions do not use a low noise receiver (common in analog TV's and digital converters), and may not get some weaker signals. One reason not to use a low noise receiver is to cut cost, another is satellite and cable TV does not (usually) require a low noise receiver.

INDUSTRY STANDARDS
ATSC - Advanced Television System Committee ( Digital TV )
NTSC - National Television System Committee ( Analog TV )

Most digital televisions can process both digital and analog signals (ATSC and NTSC), allowing the television to display analog DVD's, VCR's, and older video games.

Analog (NTSC) Televisions require a Digital Converter Box to receive OTA DTv. Most converters are also recorders. The antenna coax cable plugs into the converter box, the box is then connected with a coax cable to the televisions' Antenna Input. Some converters can also connect to the TV with video, VGA, HDMI, or YPbPr cable sets for better picture and audio quality.

Computers, Laptops, Tablets, and Smart Phones require a DTv tuner to receive TV broadcast. The coax cable from your TV antenna plugs into the DTv tuner, the tuner connects to your computer or network router / switch. You may need to download a media/TV app for your devices if you don't already have one. Some DTv tuners have 2 receivers (2 tuners) for receiving 2 different TV channels simultaneously and available on your network.

Digital (to Analog) Converters
DTv Tuners

Standard and High Definition
Over-the-air digital television can broadcast sub channels in high definition HDTV (720p, 1080i, 1080p), or standard definition (480i, 480p) resolution. The number is resolution in pixels per inch. The letter " p " stands for Progressive, picture lines are displayed one after the other. The letter " i " stands for Interlaced, odd picture lines displayed then even lines. High definition uses a wide screen aspect ratio of 16:9, or a square ratio of 1:1. Standard definition uses a ratio of 1:1, 4:3, or 16:9. The frame rate in North America is 23.976, 24, 29.97, 30, 59.94, and 60 frames per second (fps). The old analog TV system displayed an interlaced (i) picture, had an aspect ratio of 4:3, and a frame rate of 30 fps. Most Hollywood movies run at 24 fps.

Broadcast DTv Display Types
ATSC Document A/53 Part 4:2009
Definition Resolution
H x W (PPI)
Aspect
Ratio
Frame
Rate
High
Definition
(HDTV)
1080p 1080 x 1920 16:9
1:1
24 fps(1)
30 fps(2)
1080i 30 fps(2)
720p 720 x 1280 24 fps(1)
30 fps(2)
60 fps(3)
Standard
Definition
(SDTV)
480p 480 x 704 16:9
4:3
24 fps(1)
30 fps(2)
60 fps(3)
480 x 640 4:3
1:1
480i 480 x 704 16:9
4:3
30 fps(2)
480 x 640 4:3
1:1
Frame Rate
(1)
(2)
(3)
24 or 23.976
30 or 29.97
60 or 59.94
fps
fps
fps
Aspect Radio
16:9
4:3
1:1

H is height, W is width, PPI is pixels per inch.

The ATSC Digital TV Standards include HDTV, SDTV, data broadcasting, multichannel surround sound audio, and satellite direct-to-home broadcasting. See the ATSC Websiet for a list of downloadable specifications.

Ultra High Definition (UHD) / 4k resolution (next-Gen TV)
Stations will continue to broadcast using the current standard (ATSC 1.0), but will have the option to simulcast on another frequency an Ultra High Definition signal (ATSC 3.0). The UHD signal will have higher resolution, great for extremely large screens, but of little value to small and moderate size screens. UHD will also have high dynamic range which changes colors faster for a better picture. Additionally, UHD will have better reception by using new techniques that allow for a lower signal-to-noise ratio. UHD may catch on, or may go by the way of quadrophonic FM radio.

Receiver Signal Levels
Signal power is commonly measured in dBm - decibels above or below 1 milliwatt (mW). Television receivers will process signals from about -5 dBm (strong) to about -65 dBm (weak). A -65 dBm signal should come-in good for a short cable run to a single television, but may be too weak for long cable runs or signal splitters.

Signal Power
Percent and dBm

TV Receiver Dynamic Range

A television's required minimum signal depends on the receiver sensitivity and local conditions (electronic noise pollution). Minimum signal can vary from as high as -55 dBm for a TV with poor sensitivity in a noisy environment, to as low as -75 dBm for a TV with good sensitivity in a low or no noise environment. Most televisions and conditions will require a signal level of at least -65 dBm.

Estimate a TV's Minimum Signal (Show / Hide...)


Picking Up TV Signals
A little planning can insure the best results possible (see TV Tower Locator and Broadcast Reception). Understanding Reception Factors is important when dealing with distant towers, marginal or spread out signals, hilly or mountainous terrain, ground clutter, and indoor antennas. Antenna selection depends on frequency bands, antenna gain, and coverage needed. Cable loss depends on cable length(s) and connections. Outside Antennas should be properly grounded for best reception and safety.

TV Tower Locator
- Tower Map / Details
- Angle and Range
- Terrain Layout
tv tower
Reception
Steps for
getting the
most stations.
reception factors
Factors
Reasons for
weaker signal
than expected.
reception factors
Antennas
- Frequency Bands
- Gain (dBi, dBD)
- Beam Coverage
antennas
Cables
- Types / Options
- Signal Splitters
- Loss Calculator
coax cables
Amplifiers
- Preamplifiers
- Booster Amps
- Attenuators
amplifiers
Installation
- Mounting
- Grounding
- 2-3 Antennas
bowtie antenna
Frequency

Networks
reception Youtube Video
Abbreviations used in this website and common to the OTA Broadcast industry.


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