Doppler and Radio.

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Mike Therrien

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Message 926521 - Posted: 16 Aug 2009, 14:25:01 UTC

I get why your looking for doppler shifts. Can you or are you even interested in what that base frequency is of the source? I suspect that this would be needed to isolate the distance and movement of the transmission source. In addition if ET is transmitting radio waves are we looking for Carrier waves with AM or FM signals? Or is that something that will be considered once a viable source is found?
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Message 926531 - Posted: 16 Aug 2009, 15:28:34 UTC - in response to Message 926521.  
Last modified: 16 Aug 2009, 15:38:32 UTC

I get why your looking for doppler shifts. Can you or are you even interested in what that base frequency is of the source? I suspect that this would be needed to isolate the distance and movement of the transmission source. In addition if ET is transmitting radio waves are we looking for Carrier waves with AM or FM signals? Or is that something that will be considered once a viable source is found?

Seti is not looking for doppler shift as much as compensating for doppler shift around the hydrogen frequency. It is looking for any kind of persistent signal that can be differentiated from the normal radio noise of space or astronomical source. We are a long ways from worrying about the actually type of carrier or a deciphering a message. That would be an entirely different project if anything is ever found.
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John McLeod VII
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Message 926565 - Posted: 16 Aug 2009, 19:06:08 UTC - in response to Message 926521.  

I get why your looking for doppler shifts. Can you or are you even interested in what that base frequency is of the source? I suspect that this would be needed to isolate the distance and movement of the transmission source. In addition if ET is transmitting radio waves are we looking for Carrier waves with AM or FM signals? Or is that something that will be considered once a viable source is found?

SETI Enhanced is looking for narrow band signals that rise and fall with the rotation of the antenna at Aricebo. The code has to compensate for dopler shifts to see if there is a narrow band signal that is shifted because of rotations and orbits of both the transmitter and receiver.

AstroPulse is looking for broad band signals.

Once a signal is found, then we might aim an antenna full time to try to decipher the signal. But first we have to find the signal.


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Message 934466 - Posted: 19 Sep 2009, 6:12:52 UTC - in response to Message 926521.  
Last modified: 19 Sep 2009, 6:14:16 UTC

In addition if ET is transmitting radio waves are we looking for Carrier waves with AM or FM signals? Or is that something that will be considered once a viable source is found?

From what I understand, the AM/FM split in terrestrial broadcasts is split "artificially":
If a signal is centered below a certain frequency, then it uses amplitude changes to transmit information [AM]; otherwise it's frequency mod [FM]. But that's just us...
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John McLeod VII
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Message 934529 - Posted: 19 Sep 2009, 15:54:54 UTC - in response to Message 934466.  

In addition if ET is transmitting radio waves are we looking for Carrier waves with AM or FM signals? Or is that something that will be considered once a viable source is found?

From what I understand, the AM/FM split in terrestrial broadcasts is split "artificially":
If a signal is centered below a certain frequency, then it uses amplitude changes to transmit information [AM]; otherwise it's frequency mod [FM]. But that's just us...

Actually, we are looking for any signal, and we will work at interpreting it later.


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Questions and Answers : Wish list : Doppler and Radio.


 
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