Was Jefferson right? Are all HMDI cables created equal?
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January 14, 2010, 06:48 PM
Join Date: Jan 2009
In regards to interference, doesn't that not matter for digital information? I'm no expert in this field so please correct me if I'm wrong.
Actually, it does matter, but you need a lot more degradation and more noise to signal ratio to kill a digital signal than an analog one. So digital signals can suffer from interference, but because of their nature (digital) they handle it better.
A digital signal is just a kind of bits of ones and zeros. Think of it as a square waveform, or in an even cruder way, let's replace the bits with voltages, say 0 volts is the zero bit and 5 volts is the 1 bit.
Now suppose you send the code (the bits) down a wire. You get 5V and 0V on the line. Now imagine getting some outside interference in the wire. The interference (and wire resistance etc..) causes a voltage drop and change, so that instead of getting a series of five and zero volts at the other end of the cable, you get, say 3.5V and 0.5V.
That is still OK if you think about it. The higher voltage is obviously the "1" bit and the lower is the "0" bit. The signal is still understood. But if the degradation continues, you won't be able to see the difference between the "1" and the "0" bits....signal is lost.
This is why digital TV is so incredible. In the old days with over the air analog TV, a little interference with transmissions and you had banding, snow effects.., if the signal bounced off a surface and you got a strong direct signal and a very weak reflected signal you got ghosting (ghost images) etc... and all this even with just a little interference.
With a digital TV signal coming over the airwaves, the receiver is able to decode a signal and present it clearly even if there's a whopping huge interference (compared to analog).
On one channel, my tuner reported receiving something like 60% signal strength but was still crystal clear. But in some cases, the degradation is so great that the signal is lost.. so you either get a great picture... or no picture.
A very crude and simplified explanation, but I hope it helps.
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