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Old Feb 02, 2008, 08:12 PM
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Quote:
Originally Posted by Sprydle
I'd forgotten how lovely Fiona Apple is.

Physically attractive, but also a bit mentally unstable, like Tori Amos.
Old Feb 02, 2008, 09:24 PM
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Hi ya! Car ride!?
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Quote:
Originally Posted by Highflight
"Jai Guru Deva Om"

http://www.proz.com/kudoz/147309

That was one of the songs I did with the band I was in at the time, and my girlfriend sat down and listened to the record quite a few times before she got close to coming up with the "words".

HF

And just to think I'd spent the last 37 years thinking "it's not French so it must be some mumbo-jumbo the heroin (or Yoko [shudder!]) made him say." Thanks!
Old Feb 02, 2008, 11:19 PM
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Too bad it'll never make it there in a form capable of being played back. Coherent RF signals travel at most 1-2 light years. Beyond that they are undetectable noise as the signal scatters.
Old Feb 04, 2008, 02:26 PM
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Go get them Meg!
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Quote:
Originally Posted by thunder1
Too bad it'll never make it there in a form capable of being played back. Coherent RF signals travel at most 1-2 light years. Beyond that they are undetectable noise as the signal scatters.
It depends on how large the receiving array might be, and its discriminatory processing power. It also depends on the wavelength it is broadcast in.
Old Feb 04, 2008, 03:05 PM
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You don't need coherency for AM. It's also the easiest modulation to detect. And at interstellar distances, the fact that a lot of power is not part of conveying the information, therefore wasted, isn't very important.

Addendum: But the idea that even an "advanced" civilization could figure out how the MP3 was encoded is a bit of a strech. It's a stunt, no more.
Old Feb 04, 2008, 03:11 PM
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Q. How does the transmission go across the universe?
A. They slither wildly as they slip away across the universe.

Q. Where is the transmission going?
A. The words are flowing out like endless rain into a paper cup
Old Feb 04, 2008, 03:19 PM
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The most limiting factor seems to be the badnwidth of the signal transmitted:

Table 1 Detection ranges of various EM emissions from Earth and the
Pioneer spacecraft assuming a 305 meter diameter circular
aperture receive antenna, similar to the Arecibo radio
telescope. Assuming snr = 25, twp = Br * Tr = 1, <eta>r =
0.5, and dr = 305 meters.
-------------+--------------+-----------+--------+--------+-----------+
Source | Frequency | Bandwidth | Tsys | EIRP | Detection |
| Range | (Br) |(Kelvin)| | Range (R) |
-------------+--------------+-----------+--------+--------+-----------+
AM Radio | 530-1605 kHz | 10 kHz | 68E6 | 100 KW | 0.007 AU |
-------------+--------------+-----------+--------+--------+-----------+
FM Radio | 88-108 MHz | 150 kHz | 430 | 5 MW | 5.4 AU |
-------------+--------------+-----------+--------+--------+-----------+
UHF TV | 470-806 MHz | 6 MHz | 50 ? | 5 MW | 2.5 AU |
Picture | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
UHF TV | 470-806 MHz | 0.1 Hz | 50 ? | 5 MW | 0.3 LY |
Carrier | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
WSR-88D | 2.8 GHz | 0.63 MHz | 40 | 32 GW | 0.01 LY |
Weather Radar| | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Arecibo | 2.380 GHz | 0.1 Hz | 40 | 22 TW | 720 LY |
S-Band (CW) | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Arecibo | 2.380 GHz | 0.1 Hz | 40 | 1 TW | 150 LY |
S-Band (CW) | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Arecibo | 2.380 GHz | 0.1 Hz | 40 | 1 GW | 5 LY |
S-Band (CW) | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Pioneer 10 | 2.295 GHz | 1.0 Hz | 40 | 1.6 kW | 120 AU |
Carrier | | | | | |
-------------+--------------+-----------+--------+--------+-----------+

http://www.faqs.org/faqs/astronomy/f...ection-12.html

Note that these figures are theoretical. Things the signal bumps into along the way, i.e. particles and gravity, would further limit it's ability to be recieved.
Old Feb 04, 2008, 03:26 PM
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Quote:
Originally Posted by thunder1
Too bad it'll never make it there in a form capable of being played back. Coherent RF signals travel at most 1-2 light years. Beyond that they are undetectable noise as the signal scatters.
For that those beings that may hear it, can only be thankfull.
Old Feb 04, 2008, 03:38 PM
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Quote:
Originally Posted by thunder1
The most limiting factor seems to be the badnwidth of the signal transmitted:

Table 1 Detection ranges of various EM emissions from Earth and the
Pioneer spacecraft assuming a 305 meter diameter circular
aperture receive antenna, similar to the Arecibo radio
telescope. Assuming snr = 25, twp = Br * Tr = 1, <eta>r =
0.5, and dr = 305 meters.
-------------+--------------+-----------+--------+--------+-----------+
Source | Frequency | Bandwidth | Tsys | EIRP | Detection |
| Range | (Br) |(Kelvin)| | Range (R) |
-------------+--------------+-----------+--------+--------+-----------+
AM Radio | 530-1605 kHz | 10 kHz | 68E6 | 100 KW | 0.007 AU |
-------------+--------------+-----------+--------+--------+-----------+
FM Radio | 88-108 MHz | 150 kHz | 430 | 5 MW | 5.4 AU |
-------------+--------------+-----------+--------+--------+-----------+
UHF TV | 470-806 MHz | 6 MHz | 50 ? | 5 MW | 2.5 AU |
Picture | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
UHF TV | 470-806 MHz | 0.1 Hz | 50 ? | 5 MW | 0.3 LY |
Carrier | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
WSR-88D | 2.8 GHz | 0.63 MHz | 40 | 32 GW | 0.01 LY |
Weather Radar| | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Arecibo | 2.380 GHz | 0.1 Hz | 40 | 22 TW | 720 LY |
S-Band (CW) | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Arecibo | 2.380 GHz | 0.1 Hz | 40 | 1 TW | 150 LY |
S-Band (CW) | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Arecibo | 2.380 GHz | 0.1 Hz | 40 | 1 GW | 5 LY |
S-Band (CW) | | | | | |
-------------+--------------+-----------+--------+--------+-----------+
Pioneer 10 | 2.295 GHz | 1.0 Hz | 40 | 1.6 kW | 120 AU |
Carrier | | | | | |
-------------+--------------+-----------+--------+--------+-----------+

http://www.faqs.org/faqs/astronomy/f...ection-12.html

Note that these figures are theoretical. Things the signal bumps into along the way, i.e. particles and gravity, would further limit it's ability to be recieved.

There ya go. Send it out of Aricibo at S-band and you can go hundreds of light years. A terawatt isn't all that much if you digitally encode the signal with AM modulated PCM. PPM is even more efficient.
Old Feb 04, 2008, 04:12 PM
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At .1hz, it might take 431 years to send the entire song! Imagine the disappointment waiting that long to get the whole song downloaded, you hit play, and it's the Beatles!
Old Feb 04, 2008, 04:26 PM
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Quote:
Originally Posted by thunder1
At .1hz, it might take 431 years to send the entire song! Imagine the disappointment waiting that long to get the whole song downloaded, you hit play, and it's the Beatles!
I doubt that an FSK-encoded song can be decoded back into song by an alien
intelligence even if they could wait that long. And at the very low SNR's involved,
and taking into account the dispersion of the interstellar medium, I don't think
fancy modulations will work. I think it's nice that, essentially, Morse code is the
best solution to interstellar communication.
Quote:
- .- -.- . -- . - --- -.-- --- ..- .-. .-.. . .- -.. . .-.
Last edited by peterp1964; Feb 04, 2008 at 04:28 PM. Reason: oh well, I can't get the spacings to show....
Old Feb 04, 2008, 04:34 PM
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Quote:
Originally Posted by thunder1
At .1hz, it might take 431 years to send the entire song! Imagine the disappointment waiting that long to get the whole song downloaded, you hit play, and it's the Beatles!
Only if you encode very bit individually. You're figuring on transmitting about 3153600 bits per year using PCM over AM or a similar method, right, right? There's a way to boost the power while still using the same amount of energy. Use PPM, and squeeze the "on" time into a small fraction of the total time. That way you can get much more power into the information that gets sent.

That's why I recommend PPM. There's more than one way to skin a cat. Almost all the power is packed into the information. Especially at TW levels, you need the off time in order to cool the transmitters, which again, PPM lends itself to. Also PPM lends itself to an "analog" waveform interpretation rather easily, making decoding by an unknowing party that much easier. If you're willing to spend a bunch of money, at a guess, tens of TW might be possible, maybe hundreds, if you spread out the transmitting elements.

Quite a bit of laser communication uses PPM. It's the way to go when you need a lot of watts but don't have a lot of joules to spend. The big drawback to PPM is bit decoding of digital data and montonicity, but if you're sending music, I don't see much drawback.
Old Feb 04, 2008, 04:44 PM
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Quote:
Originally Posted by peterp1964
.- -.- . -- . - --- -.-- --- ..- .-. .-.. . .- -.. . .-.


He's in Washington DC. Boy, my Morse is rusty.
Old Feb 04, 2008, 05:44 PM
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I don't know what scheme is being used by NASA to transmit the signal. But I'd be really surprised if anyone working on the project expected the signal to be recieved or much less decoded by an alien intelligence.
Old Feb 04, 2008, 05:59 PM
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Quote:
Originally Posted by thunder1
I don't know what scheme is being used by NASA to transmit the signal. But I'd be really surprised if anyone working on the project expected the signal to be recieved or much less decoded by an alien intelligence.
Well, I think you're probably correct. After all, we've not heard from anybody, even though we're actively looking.


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