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Moon Bounce question
On Sat, 19 Jan 2008 14:30:12 +0000, Billy Burpelson wrote:
At the HAARP web site for the moon bounce experiment (http://www.haarp.alaska.edu/haarp/mbann.html), they display a graph that shows relative power of the incident and reflected signal versus time. They show the transmitted signal at ~ -65 dB; they show the reflected signal at ~ -77 dB. Are they implying that the round trip path loss to the moon and back is only ~ 12 dB??????? I think they're talking about the relative power *as measured at some distant point*. If you're listening at a point say, 5,000 miles from the transmitter in Alaska, you might hear the direct terrestrial signal from Alaska at -65dB, and the lunar reflection at -77dB. In other words, 12dB is the *difference* in path loss between the lunar-reflected signal and the terrestrially-propagated signal. (that difference still seems awfully small to me) Another way of putting it... if there was a ham 200 miles away doing a moonbounce transmission on 144MHz... his direct, terrestrially-propagated signal at my location would be pretty weak... especially since his antennas would be pointed up, at the moon, not down along the horizon... so I would not be surprised if the *difference* between his lunar-reflected signal and his terrestrial signal was a lot less than 252dB. |
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