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What produced the old dead channel tv static audiovisuals on tvs?

⁨179⁩ ⁨likes⁩

Submitted ⁨⁨1⁩ ⁨year⁩ ago⁩ by ⁨ALostInquirer@lemm.ee⁩ to ⁨[deleted]⁩

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  • admiralteal@kbin.social ⁨1⁩ ⁨year⁩ ago

    If you put a TV in a Faraday cage that blocked the relevant radio spectrum, would there be no static on it? I expected the answer to be a quick Google, but it wasn't.

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    • badcommandorfilename@lemmy.world ⁨1⁩ ⁨year⁩ ago

      That is a good question, but I suspect if you tried this in real life it would still show static.

      • The waves are amplified with a circuit that attempts to find a signal even if it’s very weak (so you can get a picture even if you’re close or very far from the tv station)
      • At a certain point, the electromagnetic field from the running TV itself would start to get picked up

      I suspect a better though experiment would be if you just disconnected the input and amplification circuit entirely from the CRT tube, in which case you would probably just get white as the electron beam scans back and forth without any modulation.

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      • nehal3m@sh.itjust.works ⁨1⁩ ⁨year⁩ ago

        Let me turn that around:

        Would a TV still show static if you disconnected the input and amplification circuit outside a Faraday cage?

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      • this_1_is_mine@lemmy.world ⁨1⁩ ⁨year⁩ ago

        It would just make a dot center screen.

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    • db2@lemmy.world ⁨1⁩ ⁨year⁩ ago

      You’d still see static from the TV itself and any radiation that passed in to the cage. It’s not a perfect EM blocking device like TV shows and movies would have you believe.

      en.wikipedia.org/wiki/Faraday_cage

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      • cmnybo@discuss.tchncs.de ⁨1⁩ ⁨year⁩ ago

        Even if the Faraday cage blocked all RF perfectly, the Johnson noise would still produce plenty of static.

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    • QuarterSwede@lemmy.world ⁨1⁩ ⁨year⁩ ago

      Great experiment idea.

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  • QubaXR@lemmy.world ⁨1⁩ ⁨year⁩ ago

    This is a very non scientific answer, but when I was a kid (good 40 years ago) I remember having a science book that called TV static “an echo of the big bang”. I guess that would mean just randomly scattered energy bouncing around on all bands?..

    I could probably Google it and give you an answer, but I’ll just wait for someone with a more convincingly and authoritatively written reply.

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    • bjoern_tantau@swg-empire.de ⁨1⁩ ⁨year⁩ ago

      Not all of it. But parts of it really are due to the cosmic microwave background radiation. Light from the moment the universe was transparent enough to let light spread. It’s from about 300,000 years after the big bang if I recall correctly. It’s the earliest image of the universe we have. And it’s more or less everywhere.

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    • Lemminary@lemmy.world ⁨1⁩ ⁨year⁩ ago

      but I’ll just wait for someone with a more convincingly and authoritatively written reply.

      Pfft sprayed my drink lol

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      • lando55@lemmy.world ⁨1⁩ ⁨year⁩ ago

        Probably because of how accurate it is

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      • FeloniousPunk@lemmy.today ⁨1⁩ ⁨year⁩ ago

        If it was milk, you basically created tv static on a dead channel.

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    • ALostInquirer@lemm.ee ⁨1⁩ ⁨year⁩ ago

      Now that you mention it, I remember something similar! I may have to follow up on that to see (but I’m also curious of others’ responses, hence asking).

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    • dylanmorgan@slrpnk.net ⁨1⁩ ⁨year⁩ ago

      Well apparently now astrophysicists are saying maybe the Big Bang didn’t happen. ¯_(ツ)_/¯

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      • pythonoob@programming.dev ⁨1⁩ ⁨year⁩ ago

        But it is still the result of background radiation, which is caused by something.

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      • Matriks404@lemmy.world ⁨1⁩ ⁨year⁩ ago

        That’s false. Most of them still agree that Big Bang happened, it is just that the first extra small fraction of a second of Big Bang can’t be explained with our current understanding of physics, and there is still a lot of some unanswered questions about it.

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      • Trollivier@sh.itjust.works ⁨1⁩ ⁨year⁩ ago
        [deleted]
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  • Steve@startrek.website ⁨1⁩ ⁨year⁩ ago

    IIRC, literally the background radiation of the universe.

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    • hperrin@lemmy.world ⁨1⁩ ⁨year⁩ ago

      Only a fraction, but yes. It’s cool to think those photons have been around since the universe turned transparent.

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  • nothacking@discuss.tchncs.de ⁨1⁩ ⁨year⁩ ago

    The TV will try and amplify and display any signal. Without a station, it will end up amplifying random radio noise and tiny fluctuations in the amplifier circuits themselves.

    The momentary signal strength is interpreted as brightness of a spot which is rapidly scanned over the display. In this case the signal is random so every spot on the screen will be a random brightness, changing every frame.

    Modern digital TVs won’t do this, because with compressed video recognizable data is needed to even attempt displaying a picture.

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    • lemmefixdat4u@lemmy.world ⁨1⁩ ⁨year⁩ ago

      This is the closest to the correct explanation. The reason televisions based on AM radio reception showed static is because of a circuit called the AGC (Automatic Gain Control) which worked like a robotic volume control. Its job is to keep the recovered video signal within a certain amplification range. As long as there was a carrier (the TV station was “on the air”), you’d see whatever the station broadcast. But when they turned off their transmitter, the signal strength would fall and the AGC would increase the amplification until what you see is white noise, mostly due to the random motion of electrons in the electronic components. We can minimize that by cooling, but it can’t be totally eliminated. Audio amplifiers often come with a “hiss” specification that tells you how much of this kind of noise you can expect at normal operating temperature.

      BTW, modern digital TVs -will- show a noise picture if they lack a video muting function when no carrier is detected. I have an LG bought in 2019 that does this, and it’s hella annoying when I accidentally hit the input selection button on the remote, switching from HDMI to TV reception.

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  • jeffw@lemmy.world ⁨1⁩ ⁨year⁩ ago

    Waves are everywhere. The TV picks up whatever waves it can. Some of those waves are signals meant to transmit an image, others are just random noise in our environment.

    Not an expert, but that was my understanding

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    • Rhaedas@fedia.io ⁨1⁩ ⁨year⁩ ago

      "Waves are everywhere" made me think of the Feynman's "Seeing Things" video. "Tremendous mess of waves"

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    • ALostInquirer@lemm.ee ⁨1⁩ ⁨year⁩ ago

      It’s been awhile since I’ve messed about with this, so I don’t remember (and you may not either, so this is an open question), but wouldn’t it produce the effect even if disconnected from an antenna?

      If so…Would the same principle be in play of it picking up on general EM waves to cause the effect?

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      • algorithmae@lemmy.sdf.org ⁨1⁩ ⁨year⁩ ago

        Yeah, the same way a radio tuned to a station could be static until you plug in an antenna.

        You could also get hums and interference from other sufficiently strong EMF sources, like how AM radios can pick up the sound of transmission lines

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      • someguy3@lemmy.ca ⁨1⁩ ⁨year⁩ ago

        Afaik the antenna is picking up the background waves/radiation and the TV is displaying that background waves/radiation. If you disconnect the antenna, the TV will have no signal to display, it’ll be as blank as it can get.

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      • Kalkaline@leminal.space ⁨1⁩ ⁨year⁩ ago

        The display on the screen is the strongest signal. Without a strong signal from a TV tower, you just get noise from 60 Hz AC running through the wall, or radio towers, or power lines, or whatever else makes that radio noise.

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  • ZagamTheVile@lemmy.world ⁨1⁩ ⁨year⁩ ago

    “The sky above the port was the color of television, tuned to a dead channel.” W. Gibson.

    It’s wild that this makes no, or little at most, sense to entire generations now.

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    • Davel23@fedia.io ⁨1⁩ ⁨year⁩ ago

      What do you mean? It's blue, right?

      (It's a joke. Don't worry, I get the original meaning, I'm old.)

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    • Davel23@fedia.io ⁨1⁩ ⁨year⁩ ago

      In another bit of poorly-aged prediction by Gibson, Case, the main character, brings some RAM with him to sell for a quick buck on the street. How much RAM? Three entire megabytes.

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      • ZagamTheVile@lemmy.world ⁨1⁩ ⁨year⁩ ago

        Yeah, but tbf, Case was pretty jacked up at the time.

        Also, there’s a market now for obsolete stuff.

        Image

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      • dylanmorgan@slrpnk.net ⁨1⁩ ⁨year⁩ ago

        Here’s the real question: did Gibson write Neuromancer before or after Bill Gates said no one would ever conceivably need more than 640k of RAM?

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    • QubaXR@lemmy.world ⁨1⁩ ⁨year⁩ ago

      Ha I remember that. I also recall someone in the 80s there was a pop song popular in Poland, entitled “Glass Weather”. It was about these rainy autumn evenings when there’s nothing better to do than sit in front of your (black and white) TV. The lyrics were mentioning “apartment window blue from the TV glow”.

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  • YurkshireLad@lemmy.ca ⁨1⁩ ⁨year⁩ ago

    The cosmic microwave background?

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    • Hjalamanger@feddit.nu ⁨1⁩ ⁨year⁩ ago

      Or any other waves around you

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      • Hobbes_Dent@lemmy.world ⁨1⁩ ⁨year⁩ ago

        And in you. And in you.

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  • ALostInquirer@lemm.ee ⁨1⁩ ⁨year⁩ ago
    [deleted]
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    • user224@lemmy.sdf.org ⁨1⁩ ⁨year⁩ ago

      There’s always more or less random noise, and that’s what you see and hear in analog systems. Random noise. As for why it isn’t in color, see: dsp.stackexchange.com/…/why-is-tv-static-noise-al…

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      • QuarterSwede@lemmy.world ⁨1⁩ ⁨year⁩ ago

        Ah luminance. Makes sense.

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    • nuachtan@lemmy.world ⁨1⁩ ⁨year⁩ ago

      It’s the echo that sings “I want my M-T-Vvvvvvvvvvv” right before the guitar riff kicks in.

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  • guyrocket@kbin.social ⁨1⁩ ⁨year⁩ ago

    https://en.m.wikipedia.org/wiki/Noise_(video)

    There are many sources of electromagnetic noise which cause the characteristic display patterns of static. Atmospheric sources of noise are the most ubiquitous, and include electromagnetic signals prompted by cosmic microwave background radiation,[1] or more localized radio wave noise from nearby electronic devices.[2]

    The display device itself is also a source of noise, due in part to thermal noise produced by the inner electronics. Most of this noise comes from the first transistor the antenna is attached to.[2]

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  • I_Miss_Daniel@lemmy.world ⁨1⁩ ⁨year⁩ ago

    It’s not static. It’s the ant attack.

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    • TheWordBotcher@lemmy.world ⁨1⁩ ⁨year⁩ ago

      I’m glad I’m not the only one. I remember people calling it “the ant race” when I was little (very early 90s), but no one seems to recall this.

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  • Hobbes@startrek.website ⁨1⁩ ⁨year⁩ ago

    Cosmic microwave background. You are seeing the big bang.

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  • athos77@kbin.social ⁨1⁩ ⁨year⁩ ago

    Cosmic microwave background radiation - the remnants of the big bang.

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  • Num10ck@lemmy.world ⁨1⁩ ⁨year⁩ ago

    and what happens if you broadcast static, like point it at a car thats blasting some shitty radio station, and you are transmitting that same frequency? the distortion will destroy their speakers.

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    • flambonkscious@sh.itjust.works ⁨1⁩ ⁨year⁩ ago

      I wish! The boy racers have no shame (and I might be an old curmudgeon)

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  • sagrotan@lemmy.world ⁨1⁩ ⁨year⁩ ago

    John Wayne in a Blizzard. So said my dad.

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