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Date Posted: Wed 28 Jul 2004; 11:22am
Author: James
Subject: Re: Radio transmissions in space
In reply to: D.James 's message, "Radio transmissions in space" on Mon 26 Jul 2004; 4:59pm

I found all of the threads posted in reply to my original post “Radio Transmission in Space” extremely useful and managed to gain quite a bit of useful knowledge on the subject of the propagation of radio waves in space. I will just re-cap here the conclusions that I have come to and you can tell me if they are right or wrong: (1) The propagation of radio waves in space follows the Inverse Square Law, however by using highly directional antenna on the space-craft it is possible to achieve an antenna gain of about 24dB on the transmitting antenna (i.e the antenna on the space craft. ) The use of tunnel wave tube amplifiers further boosts out-put and narrows the beam in the manner of a MASER increasing the distance over which transmissions can be made. With all this , the maximum signal that can be picked up on earth corresponds to about 10^-12 W or 120 dB. Hence , signals which are sent from very distant points must of necessity be transmitted through several links (i.e space craft or satellites ) in order to achieve the transmission over such vast distances. Does this sound more or less correct ? James

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