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How does cable TV and the internet come through a single coax cable? Answered

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There is more to it than just that. I see about 30 apartments jumped, for an emergency fix, about 300 feet. Granted the picture quality is poor but it works fine.  I do not have the same cable as my neighbor and the internet can be shut on/off over the phone. How is all this possible?

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kelseymhBest Answer (author)2010-08-28

Frequency-division multiplexing. Because coax is not broadcast, each one can use a wide frequency spectrum and split it up into different signals. By putting some data onto a frequency band your TV recognizes as "channel 3" (or whatever), you get your cable. Putting other data onto a different frequency band, and providing you with a translator box, you get TCP/IP.

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framistan (author)2010-08-30

In cable TV... each channel uses a 6 megahertz bandwidth. Without looking up the EXACT frequencies... lets say channel 2 starts at 50 Mhz...and ends at 56 Mhz. Channel 3 starts at 56 mhz and ends at 62 mhz.. In reality, the channels are spaced so that if a lower channel generates a "harmonic" signal higher up the spectrum... the harmonic will fall directly on the carrier frequency of a higher channel... this reduces interference from one chanlel to the other. The channels continue on up the spectrum in 6 megahertz chunks up to about 4 or 5 HUNDRED megahertz. Thats how it worked about 15 years ago when i worked at a cable company. Nowadays,,, they have added digital channels in the upper frequencies and have added fiber-optic trunklines. Basically that is how cable tv works. Each channel is on a different frequency band.

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Re-design (author)2010-08-28

I don't know for sure but it's probably like radio. All those radio stations are broadcasting in what's really a pretty small part of the radio spectrum, but we are still able to tune in what we want.

I'd be willing to bet that your cable and internet works on a similar principle.  And remember that cable tv is hundreds of channels.  Some you get and some you don't get.  I would imagine that what you are able to receive is controlled by a signal instructing the computer inside your cable box what to decode and what to ignore.

Your internet connection is just one of those signals coming into your house that your modem can decode.

Then again I might be wrong but I don't think so.

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nickodemus (author)Re-design2010-08-28

Sounds like a good answer to me. (The wonders of technology...)

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