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Old 01-14-2010, 7:20 PM
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prcguy prcguy is offline
Join Date: Jun 2006
Posts: 6,638

There is really only one constant which Warren touched on but I believe he got backwards.
In free space, if you double the distance the signal will drop by 6dB or 75%. In other words if you have a usable signal at 100mi in free space with 1w you will need 4w to keep the same signal level at 200mi. This is not frequency dependent however you cannot rely on this constant for terrestrial communications, even if its completely line of sight. Ground bounce and signals adding or subtracting in or out of phase can skew the results from +6dB to -20dB or more.
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