Digital TV
Tower Locator
Reception
Antennas
Amplifiers
Cables
Installation
Frequency
Networks

Over-the-Air Digital Television

PAGE CONTENTS -- Broadcast | Channels | Digital Televisions | Reception | Summary
TV Broadcast Tower

DIGITAL COMPARED TO ANALOG BROADCAST
Broadcast 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.

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,
    multiple sub-channels.
  • RF broadcast channel.

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.

Callsigns, Power and Service Types (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. 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.

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.

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 an indoor antenna (single TV), 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...)


Basic Steps for Best Reception

Concentrate on the weakest signals of interest, and the cable run with the most loss.

Basic Steps
- Find Broadcast Towers.
- Calculate Cable Loss.
- Calculate Antenna Gain needed,
or estimate existing antenna gain.
- Calculate Signal to TV's.
- Determine if an amplifier is needed.
Planning Steps

FIND BROADCAST TOWERS
Use the TV Tower Locator to find stations in your area, based on your address or latitude-longitude. Note the signal heading angles for antenna pointing, look for terrain interference, note frequency band for selecting an antenna, and look for the weakest signal of interest to see if cable loss is a factor.

From Tower Locator note;
  • Angle to Tower(s).
  • Frequency Band.
  • Possible Terrain Masking.
  • Weakest Signal of Interest.
TV Tower Locator

CABLE LOSS
Cable loss varies with frequency, the higher the frequency (the higher the RF channel), the greater the loss. In most cases using the average of a frequency band (VHF-Lo, VHF-Hi, UHF) to calculate loss is close enough. Loss can also be calculated for a specific RF channel. Cable loss also depends on cable length and the number and type (output ports) of signal splitters. Cable connectors and adapters introduce a small loss. The calculators below compute cable loss for RG-6 coax cables, the preferred cable for broadcast TV reception. See TV Coax Cable Loss for more details.

ANTENNA GAIN
For new installations, antenna gain needed can be approximated by subtracting cable loss (dB) from broadcast signal (dBm). If the result (signal - loss) is greater than the minimum signal required by the TV (typically -65 dBm), any antenna will work. If the result is less than minimum, the difference is the antenna gain needed. The gain is an estimate and should be padded 3 to 6 dB.

Antenna Gain CALCULATOR (Show / Hide...)

For existing installations estimate your antenna gain, or use 0 dBi as an easy reference. Antenna gains vary from 2 to 4 dBi for indoor antennas, to 18 dBi for high gain outside antennas. Average outside antenna gain is about 6 to 11 dBi.

ESTIMATE SIGNAL TO TELEVISION
Signal power delivered to the television equals broadcast signal plus antenna gain, minus cabling loss.

Broadcast Signal (dBm)
+ Antenna Gain (dBi)
- Cable Loss (dB)
= Signal to TV (dBm)

Signal to TV CALCULATOR (Show / Hide...)

AMPLIFIERS
A preamplifier can be used to improve weak broadcast signals. A distribution or booster amplifier should be used to overcome cable loss.


Details and Considerations
Cable loss can mean the difference between a good picture and no picture. Long cables have more loss. Signal splitters reduce power by more than half. Note reception factors that could explain why a signal is weaker than expected. A preamp close or mounted to the antenna will improve a weak signal, a distribution or booster amp can overcome cable loss. Antenna type and placement is probably the most important consideration. Outside antennas should be properly grounded for best reception and safety.

Reception
Factors
- Antenna Angle
- Terrain Effects
- Ground Clutter
- Radio Horizon
- Attic/Indoor Loss
- Summary
reception factors
Antennas - Frequency Bands
- Gain (dBi, dBD)
- Beam Coverage

- Indoor Antennas
- Outdoor Antennas
- Multi-Directional
antennas
Cables - Coax Cables
- Decibels (dB)

- Signal Splitters
- Connectors
- Adapters / Baluns
- Loss Calculator
coax cables

Amplifiers - Preamplifiers
- Booster Amps
- Attenuators
amplifiers
Installation - Restrictions Prohibited
- Mounting
- Grounding Diagrams
- Multiple Antennas
installation


Youtube Video's
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Check Terrain,
Pick an Antenna

The Movie
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Installation

The Movie



SUMMARY

CABLING
  • Use RG-6 coax cable (with F-type male connectors).
  • Cable runs as short as possible.
  • Make sure all connectors are tight.
  • Check outside connectors for corrosion.
  • Outside connectors covered with a
    rubber weather boot or electrical tape.
  • Unused output ports terminated with a 75 ohm load.
  • Install a distribution / booster amp for long cable runs.
ANTENNAS
  • Use a UHF antenna, most RF channels are in this band.
    In some cases a UHF antenna will work for VHF signals.
    Use a VHF/UHF antenna to get all bands.
  • Install an antenna pre-amp for weak signals.
  • Use a high gain antenna for weak signals.
  • Distant and spread out headings;
    • Use 2 or 3 antennas for more coverage.
    • Use an omni directional antenna for 360° coverage.
    • Use a rotor antenna for high gain and 360° coverage.
ANTENNA POSITION
  • As high as possible.
  • Clear of clutter in tower directions.
  • Pointed in direction of broadcast towers.


Abbreviations (Show / Hide...)


Over-the-Air Digital Television
Digital TV
Tower Locator
Reception
Antennas
Amplifiers
Cables
Installation
Frequency
Networks

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