Over-the-Air Digital TV (OTA DTv)
DIGITAL vs 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.
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Most DTv Stations in the UHF Frequency Band.
- Elevated terrain (Masking) blocks UHF signals.
- UHF does not bend around large structures as well.
- UHF dose not go through walls, roofs or objects as well.
- Analog antenna's will pick up digital TV signals.
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A digital television's picture and sound quality are either 100% or nothing. The picture either comes in or it doesn't, depending on signal strength. Digital TV's do have a very small power region (signal strength to TV) the picture pixelates and/or garbles the sound. Analog signals degrade a picture gradually, weaker signals have more noise or snow in the picture.
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.
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DIGITAL TV and RF CHANNEL(s)
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 television, 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 |
Digital Channel |
TV = RF
channel
|
TV Channel
-- virtual channel.
-- displayed on television.
-- multiple sub-channels.
|
RF Channel
-- Transmission Channel.
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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.
Some RF Broadcast Channels will be Changing between 2017 - 2020+
Some DTv stations will be changing channels over a 3+ year period, until about 2020 and probably longer. The FCC, at the direction of Congress in 2012, is re-allocating spectrum, forcing around 1000 TV stations to change RF Broadcast Channels. There are about 8000 TV stations in the U.S. and its' territories. See FCC Spectrum Auction Results, April 2017.
Stations Changing RF Channel
| Stations |
Percent |
Change |
| 145 |
1.8% |
Go off-the-air |
| 13 |
0.2% |
Move to VHF-Hi |
| 17 |
0.2% |
Move to VHF-Lo |
| 1000 |
12.5% |
Change UHF Channel |
When a TV Station Changes Broadcast (RF) Channels;
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The displayed TV channel will not change, but you must re-scan all TV's.
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You may have to adjust your antenna pointing angle if a station's tower location changes.
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You will need a new antenna if a station changes to a frequency band your antenna does not receive.
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A station must notify consumers with daily on-air announcements for at least 30 days prior to any change.
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PICKING UP DTv SIGNALS
Digital Televisions (DTv's) have a built-in tuner for picking up over-the-air digital TV (ATSC standard), many also can receive analog TV (NTSC standard) signals for old VCR's, video games, etc.
Analog Televisions (NTSC) require a Digital Converter Box to receive OTA DTv. Most converters are also recorders. The coax cable from the antenna plugs into the converter box, the box is then connected with another coax cable to the televisions's Antenna Input. Some converters can also connect to the television 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. Some DTv tuners have 2 receivers for receiving 2 different TV channels simultaneously.
A little planning can insure the best results possible (see TV Tower Locator and Reception Practices). 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 (Calculate Antenna Gain Needed), and coverage needed. Cable loss depends on cable length(s), signal splitters and connections. Outside Antennas should be properly grounded for best reception and safety.
Also see;