Owen Duffy wrote:

A widely accepted line loss model is that attenuation = k1 * f^0.5 +
k2 * f, your approximation makes k2=0.
. . .

In that model, k1 is attenuation due to conductor resistance, which is
proportional to the square root of frequency as long as the conductor
thickness is at least several skin depths. K2 is dielectric loss, which
is proportional to frequency for good dielectrics. So this model is good
for common transmission lines like coax or dry twinlead, at HF and
above, but not necessarily valid for loss due to water. I commented more
about this in another posting.

Roy Lewallen, W7EL