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linear development of television transmission

Discussion in 'History' started by Days, Aug 26, 2012.

  1. Days

    Days Governor

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    We live in a digital world that takes the old analog signal and digitalizes it. That process is far more complicated than anything I will post here, but because we live in that world, we understand what digital television is. Originally, television was created by taking a series of pictures in rapid succession (guess what: today's television is still created the same way) and then displaying that stream of pictures (the signal) on a monitor. In the 1940's we figured out how to broadcast television signals the same way we did/do radio signals. Television signals required more bandwidth and carried both picture and sound. Next we learned how to send the television signal from station to station with parabolic dishes. The dishes create a beam which then can be sent from "hop" to hop... radio towers with 8 foot dishes were spaced 25-35 miles apart utilizing "line of sight" technology; which just means the signal beam was aimed at the 8 foot dish on the next tower, which then beamed it to the next tower; each tower had a 8 foot dish to receive the signal and another 8 foot dish to transmit it on again. The frequency used was microwave. Microwaves are the same size as a molecule of water, hence they oscillate the water molecule (cook it) and therefore the signal is easily interrupted by weather. Once the signal was transported from one station to the next, it could be broadcast in another region. When the signal is broadcast, it is sent out in a wave in every direction, the same as light from a star. The analog signal had a broadcast range of roughly 100-200 miles depending on the amplitude. After the signal dissipated over enough distance, the signal would "break up" or simply become too thin to receive by a receiver. In theory, an electromagnetic wave will carry into infinity, in practice, it has very definite range limitations. However, when the signal is transmitted as a beam from a parabolic dish, the signal holds together for much greater distances. And when that signal is pointed towards the heavens, it only has to penetrate 10 miles of weather (the biosphere) before it reaches an unencumbered environment. The signal is still an electromagnetic wave, so it will eventually spread out and dissipate. In the 1960's we learned to go to larger dishes (15-20 foot) and stronger signals and was able to transmit between earth and satellites orbiting 300 miles+ above the earth. Then, in 1964, we figured out how to get a satellite to work in the Clarke orbit (22,000 miles out) which is a geo stationary orbit, which means the orbit remains in a fixed relationship to a spot on earth. The very first successful satellite launched in this orbit was fixed over the Pacific Ocean and the very first LIVE television broadcast (signal) to be transmitted across the Pacific Ocean was the 1964 Tokyo Olympics. In order to transmit that signal to the Clarke orbit and to fetch it back again, we built 85 foot dishes. That was cutting edge analog television technology in 1964. In 1965, the Apollo space program ordered up two more 85 foot dishes from the same industry to be used to send and fetch the same analog television signal to/from the moon. The moon is 11 times farther away than the Clarke orbit. In the days of analog, that was called, way out of range. However, the 1964 satellite fixed over the Pacific Ocean was in perfect operating range... and was already functional... as long as the ground bases were Pacific Rim, which they were. The ghost images of Apollo 11 were the result of the complicated broadcast signal that tore the signal apart and packaged it into a smaller bandwidth; that signal had to be reassembled when it was received... it took them a mission to get that process down... it was a lot more complicated than mere tuning. The common misconception is that the ghost images resulted from being out of range... as in, the moon was out of range. Actually, when you were out of range, you get no signal: you get fuzz... if you were barely in range, you would get a faint signal mixed in with the fuzz (they called it "snow") but what Apollo was getting was a strong signal that double imaged on them... they were well within range... of the Clarke orbit.
     
  2. BrianDamage

    BrianDamage Council Member

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  3. Days

    Days Governor

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    I had all those old television Links and Apollo television Links in my old computer that fried on me in the Spring of 2008. I studied early television through the internet (I've been all through the Link you provided and a 100 more like it) and I try to give a succinct summary of the story they tell. It is real easy to get bogged down in techno-journalism. For instance, how important is it for the reader to understand nodes?

    RCA had the main contract on the television equipment for the LEMs. RCA went bankrupt decades ago. None of their Apollo work has made it onto the internet. But there was a ridiculous disconnect between the fixed two foot dish, on top of the LEM, that supposedly sent the signal that contained Armstrong stepping down the ladder, and the 1959 built microwave dish in Australia that supposedly received that signal. They didn't even bother to point the two foot dish at earth; it was on top of the roof, pointing upward; but it was a dish! If the dish isn't pointed directly at the earth, the earth has to pick out gain from the edges of the signal... aka, 95% of the signal was lost. So what are the odds that the Eagle landed on the moon with the two foot dish coincidentally zeroed in on the earth? Slim to none. If this was a real landing on the moon, the dish would be adjustable and the agenda for leaving the hatch would include a period for adjusting the dish to zero in on earth and some testing for crying out loud.

    It's all moot. The low power signal through that two foot dish had a maximum operational range of 800 miles, and that's only dead on where the dish is aiming. The 200 foot dish on the ground wasn't pulling in a strong enough signal to hold the bandwidth of the moon broadcast from any further out than 50,000 miles. That's a 180,000 mile disconnect.

    Today we put light through a radical chamber and then attach digital coding to the laser as it leaves the gun... and stream whole new operating software to rovers on the surface of Mars. We are within range of the lasers to do that.
     
  4. BitterPill

    BitterPill The Shoe Cometh Supporting Member

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    No it isn't. Actually, most of the Earth's atmosphere is, what, ten or so miles thick, and beyond that there isn't anything to impede the signal, so a low power transmitter can easily reach us from the moon.
     
  5. Days

    Days Governor

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    Didn't read the top post, did you?
     
  6. NightSwimmer

    NightSwimmer Senator

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    Your top post doesn't change the laws of physics.
     
  7. Days

    Days Governor

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    No, it doesn't. It just explained how they apply to the analog television signal and what range limitations that resulted in. If there was no range limitations, they would not have needed to build larger dishes... heck, they would have never bothered to build dishes.
     
  8. Bo-4

    Bo-4 Senator

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    Days.. again, you know i love ya but stop acting like Republicans!!

    Please?
     
  9. Days

    Days Governor

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    huh?
     
  10. BitterPill

    BitterPill The Shoe Cometh Supporting Member

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    I did, and you can quiz me on it: a lot of words claiming a low power transmitter couldn't reach us from the moon. I hope that's right.
     
  11. Days

    Days Governor

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    Are you familiar with the electromagnetic wave spectrum? Do you grasp the basic physics of wave dispersion? Think about the beam of light produced by a flashlight... shine it on a wall from three feet and back up ten feet and watch what happens. The silver reflector cone in a flashlight is not shaped in a parabolic dish, but the properties of the electromagnetic wave are the same in the analog signal... it is slowly going to disperse and weaken in intensity until it finally becomes so weak it can not be received by a receiver.

    that's the part I wanted you to notice.
     
  12. BitterPill

    BitterPill The Shoe Cometh Supporting Member

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    It's still going to be enough.

    Do you think the new Mars Rover is also a fake?
     
  13. Days

    Days Governor

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    Nope it wasn't enough, it was about 180,000 miles short of being enough.

    The stuff happening on Mars is 150 million miles away; way and far out beyond the nearby moon, heck, the sun is only 93 million miles away. But digitally coded light shot from a LASER can make it there. Mars rovers are no hoax.
     
  14. GordonGecko

    GordonGecko President

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    Days, did we land on Mars in 1976 with Viking?

    Just want to see how far it goes with you.
     
  15. OldGaffer

    OldGaffer Governor

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    What is the power of the Mars transmitter? It is sending a signal, what, 80 million miles? In high definition.
     
  16. Days

    Days Governor

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    I believe in the space program. Jeff Carr, son of Gerald P Carr, commander of skylab4, was my best friend in college. I met the old man, talked with him. I asked him what was the most amazing thing about space? He answered, "the stars were incredible". Never forgot that.

    The Viking was not a manned mission. You need to draw that distinction. The Viking was transmitting in digital, not analog. Those early digital missions were transmitting in bytes, not kilobytes. The Voyager probes took pictures of the planets and streamed that info back to NASA, but you won't find any actual pictures from those transmissions; think computer graphics in the 1970's... NASA hired artists to give their renditions of the planets from information gleaned from the probes.

    Remember the Helios probes of 1984-86? That's when we began to learn about the solar wind and micrometeorites; things Apollo was not equipped to navigate. You haven't read my threads, neither has old gaffer. It shows. I cut through all the grease for you guys and do you appreciate it? You don't even know I'm doing that for you.

    If you can't appreciate the science - and you can't - maybe you can grasp the cinematography. A few years back, someone noticed that the visors in the Apollo clips were reflecting the lighting in their studios; instead of the sun. That's when we began to realize that all the clips in low earth orbit were done on location, but all the clips supposedly shot on the moon were shot on the set....

    [video=youtube;BBJUyYuzivo]http://www.youtube.com/watch?v=BBJUyYuzivo&feature=player_embedded[/video]
     
  17. GordonGecko

    GordonGecko President

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    So, Days...

    in 1969, it was "impossible" to broadcast from the Moon....

    but only SEVEN YEARS LATER it was possible to broadcast from Mars?

    Ah-ha.
     
  18. Days

    Days Governor

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    They never broadcasted from Mars... the latest rover is able to send pictures back, not video.

    What I am pointing at is the range limitation of the analog signal.

    The LASER doesn't have those range limitations. Plus, the information transmitted is digital code, as long as the light arrives, the code is onboard. It is a completely different signal from analog.

    Those mid 1970's communications were the first digital code attached to the microwave signal. The voyagers (late 1970's) could attach a whopping two bytes per second (going by memory, here) ... not exactly enough bandwidth to broadcast, not really enough to assemble pictures, but it didn't require any amplitude, it was a low power signal that could carry code from a long way off in the solar system.
     
  19. Spamature

    Spamature President

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    OK I give up. NASA is just a scam run by flim flam artist. And that Curiosity Rover is really a golf cart with a camera on it driving around in the desert on the outskirts of San Bernadino. It's only a matter of time before its rover jacked or hit by taggers. Then they can claim "it lost power" and con us out of another $4 billion for a new one.
     
  20. NightSwimmer

    NightSwimmer Senator

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    There is no such thing as a digital wave transmission.
     

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