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#1
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A local SWL who is friend, yes I do have some, called me wondering
about the threads regarding fading. Will has only been into SW a few years and comes from a non electrical background and the debate got him wondering. I found a link that I sent him and he said it made it much clearer. For those amoung use who might not have a clear visualization I offer this link. http://www.tpub.com/content/et/14092/css/14092_19.htm If the "reflection" or refraction points, E and/or F, move then the signal at A will suffer from distortion. Not much movement is required to really "mess" a signal up. A similar effect can be heard on the song "Itchycoo Park" by the group Small Faces where two reel to reels, each with the audio information, were mixed and one was slowed down by touching the outer reel edge, a technique called "Flanging". The slightly different audio sources mix creating a comb fitler effect. Higher audio frequencies are effected more then lower, hence the interest in effective audio low pass filters. When done with white or pink audio noise and viewed with a FFT program, "notches" or deep valleys appear in the display. Today effects boxes use digital delay lines to achieve this effect. Terry |
#2
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Think of yourself as under a sea of water with a flashlight. The surface
above you with random waves occilating about in a psuedo-random fashion. If you shine a light at an angle towards the surface the light is reflected back down towards the sea floor in a fashion that is a function of the occilating waves above you. A person (receiver) looking for the light at the sea floor may or may not see the light depending if the waves are relatively calm or are raging in a typhoon. Then there is function of the clarity (rf conductivity) of the water itself... etc... wrote in message oups.com... A local SWL who is friend, yes I do have some, called me wondering about the threads regarding fading. Will has only been into SW a few years and comes from a non electrical background and the debate got him wondering. I found a link that I sent him and he said it made it much clearer. For those amoung use who might not have a clear visualization I offer this link. http://www.tpub.com/content/et/14092/css/14092_19.htm If the "reflection" or refraction points, E and/or F, move then the signal at A will suffer from distortion. Not much movement is required to really "mess" a signal up. A similar effect can be heard on the song "Itchycoo Park" by the group Small Faces where two reel to reels, each with the audio information, were mixed and one was slowed down by touching the outer reel edge, a technique called "Flanging". The slightly different audio sources mix creating a comb fitler effect. Higher audio frequencies are effected more then lower, hence the interest in effective audio low pass filters. When done with white or pink audio noise and viewed with a FFT program, "notches" or deep valleys appear in the display. Today effects boxes use digital delay lines to achieve this effect. Terry |
#3
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![]() SeeingEyeDog wrote: Think of yourself as under a sea of water with a flashlight. The surface above you with random waves occilating about in a psuedo-random fashion. If you shine a light at an angle towards the surface the light is reflected back down towards the sea floor in a fashion that is a function of the occilating waves above you. A person (receiver) looking for the light at the sea floor may or may not see the light depending if the waves are relatively calm or are raging in a typhoon. Then there is function of the clarity (rf conductivity) of the water itself... etc... Thanks, Will called me just know and said you explanation makes it much clearer. Terry |
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