How does television static work?

[Church_Key_Kid]

How does television static work? Is the television merely broadcast radio waves that occur naturally in nature, or is it some form of safety mechanism built into the television?

Since a television has a fixed resolution, is there a limit to the number of black pixels that can be on the screen at the same time (ie, could the screen be all black or all white, or must it be half & half)?

Is the pattern of black and white static completely random?
Could the static be used to seed a random number generator?

[Eternal]

What I’d like to know is why I see images from a DVD or VCR that are on the TV in one room are in the static on the TV playing in the other room.

[Desmostylus]

*Originally posted by fatdave *
**How does television static work? Is the television merely broadcast radio waves that occur naturally in nature, or is it some form of safety mechanism built into the television? **

It’s a combination of:

• thermal noise in the TV circuitry
• man-made radio waves
• naturally occurring radio waves, e.g. from the sun

*Originally posted by fatdave *
**Since a television has a fixed resolution, is there a limit to the number of black pixels that can be on the screen at the same time (ie, could the screen be all black or all white, or must it be half & half)? **

If it’s truly random, it’ll average to grey. But’s there’s no limit on the ratio of black area to white area at any given instant.

*Originally posted by fatdave *
**Is the pattern of black and white static completely random?
Could the static be used to seed a random number generator? **

If you isolate the TV from man-made sources (e.g. at least by unplugging the antenna), then the pattern is pretty random. You could use it to seed a random number generator, or to directly generate random numbers. There are better ways to do this, however.

[antechinus]

Apparently the noise is partly (~25%) from the cosmic background radiation left over from the big bang.

A cite

[Desmostylus]

Um, where do you get the 25% figure from, and how do you relate the microwave background radiation to the broadcast frequency radiation?

[Q.E.D]

*Originally posted by Desmostylus *
**Um, where do you get the 25% figure from, and how do you relate the microwave background radiation to the broadcast frequency radiation? **

From the cited site:

About one fourth of the static-ey blips of light that swarm around on your television screen are caused by the cosmic microwave background, and come from the Big Bang.

I don’t know, but when I went to school, one fourth was the same as 25%. Of course, the site is wrong in regard to the nature of the cosmically-generated static. It’s not from the microwave background, but rather is caused by high-energy cosmic rays, which occasionally interact with the antenna and induce a voltage pulse. I can’t find a cite for it at the moment, but IIRC, the figure was closer to 1%.

[antechinus]

So is the story that TV static is part CMB radiation a myth?

Is the TV antenna unable to pick up microwave frequency and show it as noise or is the CMB noise overwhelmed by other sources of noise?

[antechinus]

Could an experiment to test this be - put the TV in a faraday cage and measure the static drop?

[Q.E.D]

Well, my TV doesn’t pick up any sort of signal from either my cell phone or cordless phone, that I can tell. TV tuners are pretty tight filter networks, and very little outside the tuned range gets through, unless the power density of the incoming signal is very high, which it wouldn’t be for CMB radiation.

Your Faraday cage experiment would have to control for all other sources of radiation, including local noise from equipment in your home and surrounding areas, solar radiation and other background EM fields, as well as the internal thermal noise of the television set itself in order to generate any meaningful results.