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Whatever signal comes out of a digital antenna carries many basic broadcast channels (ABC, FOX etc.) Once this signal reaches the TV, some extraction circuit extracts (or tunes to) the channel I want to watch. If all this is true, then, why can I store the raw signal coming from the antenna on a device, and extract the desired channel(s) later as needed?

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closed as off-topic by W5VO Dec 28 '16 at 19:03

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  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – W5VO
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  • \$\begingroup\$ What makes you think you can? \$\endgroup\$ – Wouter van Ooijen Dec 28 '16 at 18:56
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You can, and this is what a software defined radio does. The only requirement is that your sample rate in the recording is sufficiently high to capture the entire range of frequencies you wish to record, and that the bits per sample provide sufficient dynamic range.

It should be noted that a "digital antenna" actually outputs an analog signal. In fact it's not digital in any sense, except that it's designed to receive the frequencies used for digital television. The signal does not become digital until after it's demodulated by your TV.

Depending on regional details of course, the digital TV broadcast band goes from approximately 470 to 700 MHz. That means the band is 700 - 470 = 230 MHz wide, meaning a sample rate at least twice that is required: 460 MHz. Considering the typical computer sound card (and MP3s, CDs, etc) typically has a sample rate of 0.048 MHz, recording the entire TV broadcast band would require some specialized equipment, and the recording would be relatively large.

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