water and ground waves in DX

[Dan Strassberg]

SALT water is what really helps. It has a conductivity of 5 S/m, whereas the
soil around here has a conductivity of roughly 2 mS/m (less in many places).
At reasonable distances (up to 100 miles or so), there is not much
difference between medium-wave propagation over salt water and medium-wave
propagation over a sheet of pure copper. This is, of course, a theoretical
calculation, since there is no place on earth where a 100-mile sheet of
copper exists. Anyhow, salt water is roughly 2500 times as conductive as
most of the dry land in the Boston area. Fresh water is only about four
times as conductive as typical New England soil. Tidal mud flats are about
as conductive as salt water itself. Although the soil conductivity does
improve after a drenching rain, the effect is not as great as having the
signal arrive via a salt water path.

If you believe the FCC's soil conductivity maps, the soil conductivity in
much of Kanasa, Nebraska, and the Dakotas is five times that of the fresh
water in the Great Lakes, although I don't think the FCC took conductivity
data in the Cleveland area thirty years or so ago when the Cuyahoga River
caught fire ;>)

--
Dan Strassberg, dan.strassberg@att.net
eFax 707-215-6367

----- Original Message -----
From: Bob Nelson <raccoonradio@yahoo.com>
To: <boston-radio-interest@bostonradio.org>
Sent: Sunday, November 16, 2003 10:44 AM
Subject: water and ground waves in DX


>
> So I guess living next to the ocean AND having
> "wet ground" would help my daytime (and nighttime)
> AM DX, eh?