Losses due to water in co-axial cables.

It is comonly assumed that the purpose of the air space in co-axial cables is to lower the dielectric constant of the dielectric medium because lowering its dielectric constant will reduce the losses of the cable.

In fact the I squared R losses due to the presence of water are due to the loss tangent of the water and not the high dielectric constant. Capacitance is a passive element which in the ideal case dissipates NO power.

Power Factor PF = cos () = tan d / Ö( 1 + tan2 d ) = tan d Approx

Pure water Density 1

k' 15 to 50

This is the dielectric constant at microwave frequencies, it does go as high as 80 in some publications.

tan sigma 0.3

Therefore the power factor of water is 30%

The only thing to affect the cable losses are the resistive elements and the series and shunt resistances, in this case tan sigma of the water.

As the formula, (I^2*R), shows the capacitance does not figure .

Credited to Gary G7SLL