The same information that GroundUrMast gave about A/B antenna switching and Tv tuner adding channels.
-->Is Also True with 1 antenna on a antenna rotator , Rotating the antenna around and then scanning for more channels.
From the Tv tuners point of view , this is the same as 2 antennas.
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Some , ->not all<- notice the words not all , Older Digital Tv's have tuners that do not add channels during - rescans/scan add - and have no provision to add new channels manually one at a time.
If you have a digital tv that does not add new channels without deleting the previous scan , here is a way to deal with the situation.
Add a external tuner , second tuner , a easy way with out complicated adding a tuner to a computer and the computer programs that operate it is,
A stand alone tuner , such as , ePvision Digital tuner
http://www.epvision.com , or , a Channel Master Digital tuner
http://www.channelmasterstore.com.
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If the the Tv reception is in one direction Only then there are no problems.
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YES most Digital Tv's will - add channels - scan add channels - and most of the Better Digital Tv's will also Manual add Tv channels.
Please note that when adding channels one at a time , it is the Real and Actual channel that is add , not the virtual number.
Tv fool lists the Real channel and the virtual number , and can also contact the Tv station for the Real channel and virtual number information.
Most likely you will need to contact the engineering department at the Tv station because every one else in the building will not know.