Reception DTV scan and recan to receive over the air broadcast TV channels

Converter Box (settop box)

Steps

1. Connect your DTV converter box to a good antenna. If you are using rabbit ears that you have to adjust differently for each channel, you might wish to ask a neighbor who has a good rooftop TV antenna if you can temporarily connect your DTV converter box to his antenna to do the scan (most good DTV converter boxes will "remember" the channel scan information even if you unplug the power to take it back to your house).
2. Use the remote control for your DTV converter box to enter the "channel scan" mode. Some remote control units have a button for "CH SCAN", while for others you must enter the "MENU" mode and navigate to the "AUTO CHANNEL SCAN" or "AUTO TUNING" function. The first scan should be a "full" auto scan, not a "channel add" scan. A "full" scan completely rescans, removing previously memorized channel frequencies (since many channels used for DTV broadcast changed).
3. Start the "Scan" function. The DTV converter box will examine all the TV channel frequencies (2 through 69) and if it finds a DTV broadcast, it will memorize the that frequency and the call letters and DTV virtual channel number associated with it.
4. After the full autoscan has completed, use the "channel up/down" buttons on your DTV converter box remote control to verify that all the channels you expect to see are there. The virtual channel number appears first, then a dash (-), then subchannel numbers starting with 1. If you expect to see a channel 11, for example, be sure that "11-1" is one of the channels that appears as you traverse the channels.
5. If not all the channels appear, follow the "tip" below regarding adding of channels using a "channel add scan" or "manual tuning" function to add channels to the list of memorized DTV channels that your converter box stores.

  Tips

• Some DTV converter boxes have a "signal strength" bar that helps you adjust your rabbit ears (or other antenna) for the strongest DTV signal on the channel you are watching. This function works slowly, so pause a few seconds after each adjustment to allow the indicator to update.
• Some DTV converter boxes allow you to add channels without doing a complete re-scan, by forcing it to look for a DTV signal on a particular RF channel frequency, or doing a "channel add" scan (without deleting previous scan results). This is useful if your antenna must be adjusted to different positions to receive different channels (you can do multiple scans with the antenna in different positions to add channels to the memorized list without deleting any previous scan results). This document[3] lists various converter box models their features. Scroll down to "ADDITIONAL/ADVANCED FEATURES" to determine channel scanning/adding capabilities. Under "Adding Channels" the word "None" indicates the box can only do a full scan, replacing previous scan results, not add to the previously memorized channel list. The "channel add" feature (called "EZ Add" on Zenith models), denoted by the word "Scan" under the "Adding Channels" column, indicates the capability to do a scan which adds DTV channels found to the existing channel list without erasing the results of previous scans. The word "Direct" under the "Adding Channels" column indicates the capability to manually add a channel to the list of available channels by entering a known RF TV channel frequency (which can be found here for a station in your area under the column "Channel Numbers/Digital").
• If your antenna is not very good, your DTV converter box might miss some channels that are really there but just not received because the antenna isn't adjusted well enough for that station during the scan. In that case try to temporarily connect to a better antenna during the scan, or if your converter box allows it, force the converter box to manually tune to the RF channel frequency of the station you are trying to add while adjusting the antenna. See this table to find the actual post-transition RF TV channel number that the station will be using for its digital broadcasts.
• Once you get a good scan of all the DTV channels after June 12, 2009, if your antenna is not very good (such as rabbit ears) and you need to add channels in the future, it may be better to try to add additional channels (using a "channel add" scan or manual entry of RF TV channel number if your converter box has either of these capabilities) rather than doing a complete automatic rescan (which erases previous scan results) to avoid the risk of missing some channels that you scanned last time (due to your antenna being in a different position).
• If you have any questions or suggestions please feel free to post them on the "Discussion" page for this article (press "Discuss" tab near top).

source: http://www.wikihow.com/Scan-for-DTV-Channels-Using-a-Digital-TV-Converter-Box

DTV Television set (typical Vizio set)

How do I perform a channel scan?   If you are using a Cable or Satellite box connected using AV, Component or HDMI cables you will not need to do a channel scan as the box you are using works as the tuner and you will not be using the tuner inside your television. You will also want to ensure that your television is on the correct input for the cable type you are using.

If you are using the coaxial input then you will want to take the following steps to perform a channel scan:

• Ensure that you are on the "TV" input
• Open the Main Menu and select the "TV" option
• Select Tuner mode and ensure that the correct option is selected,(cable or antenna)
• Next choose Auto Search
• When the TV reaches 100% complete then Exit the menu
• Press your channel up or down button to view the channels you have available

If this does not resolve the issue we recommend clearing the TV memory, resetting the settings and re-running the channel scan.

Please follow the steps in this order:

• Power off TV
• Unplug TV from outlet
• Press and hold in the power button on the TV for 30 seconds (while it is unplugged from the wall)
• Release the power button
• Plug in the TV into a different outlet
• Power the TV back on

There is also a factory reset option in your menu under the SETUP section. It will say either "reset all settings" or "system reset".

Once the above steps are complete please remove the cable connection from the DTV/TV connector on the back of your television and run a channel scan to clear out the existing channels. How do I do a channel scan?

Once this is complete plug the cable line back in to the DTV/TV connector and run a new channel scan.

source:=  https://vizio.custhelp.com/app/answers/detail/a_id/100/~/how-do-i-perform-a-channel-scan%3F