How was video transmitted when using a cable box?


How was video transmitted when using a cable box?

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On the most basic level, the cable company is sending in signals for every channel, but the frequency is different for each channel.

If we compare it to music, there is a lot going on when you listen to a song. A lot of sounds hit you at once, but if you want to focus on the singer, you can. If you want to focus on the drums, you can.

At least to a limited extent, you have the ability to tune out certain sounds.

Your cable box is a bit similar. If you tune to channel 5, it knows what frequency channel 5 is, so it looks for that frequency, and tunes everything else out.

Old televisions tuned to the high VHF and low UHF bands to receive aerial signals through a roof mounted antenna. The VHF band held 13 channels (I think) and the UHF had another 20ish I think (writing off the top of my head. Someone can correct me).

Anyways, whay limited the channels was the frequency allocations in those bands. Each channel occupied a portion of its band around a specific frequency. The television portions of the band were limited since VHF and UHF bands served other communications too. Also, television stations were reasonably sparse, so many markets received far fewer channels than TV could tune.

To get more channels to TVs, cable companies collected channel signals from many stations, and then re-broadcast all of them on a single coaxial wire to each home. The beauty of the technology was in its simplicity. Cable companies squeezed dozens of channels into a single wire by simply re-broadcasting the the received radio signals directly into coaxial RF cable, as if each customer plugged in a super antenna into their TV. The cable company had the antennas, and charged customers a fee to plug a *cable* into their feed.

Because each channel occupies a discreet frequency range, the RF cable can convey them all simultaneously. And because the cable is shielded, frequencies not available to aerial broadcasters were safe to use with no chance of harmful interference with other radio communications. Suddenly, the potential to receive hundreds of channels existed.

But most TVs could only tune aerial channels (maybe it was 24 total or something). Broadcasters usually fed national networks for free, often as far as channel 13 and beyond, since coverage most of these channels coverage for many of these was widespread. Anyone with rabbit ears could receive these almost amywhere.

were these occupied So the cable company gave you a decoder that could tune each chammel and feed it to your TV’s channel 3 input (arbitraty standard back then).

And that was it. If your friends were lucky enough to have cable at home, it was fun to visit and watch shows or movies not available on your own TV.

That was the TV Guide era.