Over-the-Air Digital TV (OTA DTv)
Contents -- Digital vs Analog TV | Digital Channels | Incidentals
One of the first steps to getting free DTv is to find transmitter towers in your area. Then with a little planning, and understanding best reception practices (Getting Free TV) and signal factors, you can get the most stations possible. Antenna selection depends on frequency bands, coverage, and antenna gain needed. Signal loss from cabling depends on cable length(s), signal splitters and connections. Outside Antennas should be properly grounded for best reception and safety.
|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.
A digital television's picture quality is either 100%, or nothing. There is not a gradual degradation of picture for weaker signals, it's a steep cutoff. In contrast analog pictures degrade gradually, weaker signals have more noise or 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.
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. Digital channels are the virtual TV channel, then a dot or dash, then sub-channel number (e.g. 6.3 or 6-3). The number of sub-channels varies from 1 to 7 or more.
- the broadcast RF channel.
|Analog TV||Digital TV|
|TV = RF|
| .Sub-channels |
1 to 7 or more.
|RF Broadcast Channel|
A stations's TV channel could be the same as it's RF channel, but in most cases they are different.
In 2009 most analog stations changed their RF channel (and most VHF stations moved to UHF) for the DTv transition, but were allowed to keep their old analog channel identification as their TV or Virtual channel. The 2017 spectrum reallocation has over 10% of stations changing their RF broadcast channel, but not their virtual TV channel.
Sub channels can be in high or standard definition resolution. Audio can be in monotone, stereo, or surround sound. Most sub channels have program guides, closed caption, language, and other options.
Cable and satellite operators often compress local 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.
SOME STATION'S CHANGING RF CHANNELS BETWEEN 2017-2020+
Some DTv stations will be changing RF 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.
|13||0.2%||Move to VHF-Hi|
|17||0.2%||Move to VHF-Lo|
|1000(1)||12.5%||Change UHF Channel|
When a TV Station Changes Broadcast (RF) Channels;
- The displayed TV channel will not change, but you must re-scan all TV's.
- You may have to adjust your antenna pointing angle if a station's tower location changes.
- You will need a new antenna if a station changes to a frequency band your antenna does not receive.
- A station must notify consumers with daily on-air announcements for at least 30 days prior to any change.
Television Broadcast Frequencies
A television Radio Frequency (RF) channel is allocated 6 MHz of bandwidth for over-the-air transmission in the VHF or UHF frequency band. The VHF band has 12 RF channels (2-13). The band is sometimes subdivided into VHF-Lo (channels 2-6), and VHF-Hi (channels 7-13). The UHF band originally had 70 RF channels (14-83), but was later reduced to 56 channels (14-69). Note, channel 37 is reserved for radio astronomy, leaving 55 UHF channels for TV broadcast.
|TV FREQUENCY BANDS|
|Television Frequency Bands (MHz)|
|VHF -||Very High Frequency||30||-||300||MHz|
|UHF -||Ultra High Frequency||300||-||3000||MHz|
-- Reception Factors Wavelength Calculator.
-- CopRadar.com/ Radio Frequency Bands.
Television VHF Band (54 - 216 MHz)
|VHF-Lo (54 - 88 MHz)|
|VHF-Hi (174-216 MHz)|
Television UHF Band (470 - 806 MHz)
| Few Stations|
| No Longer Used for TV|
Channel 37 is reserved for radio astronomy.
A few stations still use channels from 52-69.
|Over-the-Air Digital TV (OTA DTv)|
Television Broadcast Frequencies
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