Don White wrote:

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?


Don't know how to calculate that...but in our VHF course we were advised
to use the 1 watt when in a small harbour or at an anchorage. The idea
was that 25 watt was overkill in this situation and would add to the
clutter for people a fair distance away.

Crap clutter Don where in the Harbor, as many wats as you want. Harry
your 1 watt is good for boats that are around you and probably not much
more, the 25 will almost get you to Washington and the Bush minions.

Assuming the simplest model (probably wrong), the antenna height
shouldnt matter cuz VHF is s'posed to be line of sight but assume it
is. So you use 1/r^2 and get that 1 watt should reach 1/5 as far as 25
watts. This is prob close enough but I bet there's some refraction and
bending of the pattern 'n such along the earths curve that might depend
on total power (I am not sure how it would depend on power though).