25/d1^2 = 1/d2^2

d1 = 12 so d1^2 = 144

25/144 = 1/d2^2

144/25 = d2^2

d2 = 2.4


"Jim Richardson" wrote in message
...
On Fri, 16 Sep 2005 16:43:10 -0400,
Harry Krause wrote:
With my VHF tranmitting at 25 watts, I can easily reach out from one
side of Chesapeake Bay to the other in most places.

At the 1 watt setting, who knows?

For the sake of discussions, let's say on a clear day from my VHF
antenna, which is approximately 14' above the waterline, a 25 watt
transmission reaches someone 12 miles away with a similar antenna height.

Is there a way to figure how far a 1 watt setting will reach with the
same equipment?




If you assume that conditions are identical (like you are switching
between 1W and 25W settings, rather than on different days), and that
the reciever you are being picked up on, has a sufficient noise floor
and min sig sensetivity, then it's a pretty simple inverse square. There
are some other issues, like very low signal losses in antennas, which
don't scale linearly with power, but as a rough guess, you can probably
reach about 1/8th the distance, under ideal circumstances.


--
Jim Richardson http://www.eskimo.com/~warlock
The laws of physics are not subject to judicial review.