A correction - insert dt instead of dz.

The fundamental partial differential equations of transmission lines
are -

- dv/dz = R + L*di/dt

- di/dz = G + C*dv/dt

where volts v and current i are incremental functions of distance and
time, and z is incremental distance along line.

Everything else follows.

Similar equations can be written in terms of frequency.

It is often easier to think in terms of Time and Distance rather than
Frequency and Impedance.
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Reg.