Speed in telegraph equation

Question

From the telegraph equation, it is found that electrical signals travel at fraction of light speed over transmission lines. For copper cables, the speed is about 0.5 c.

Is such speed experimentally verified. Can someone point to some experiments verifying the telegraph equations.

[edit] Is this thought experiment valid: 1) I have a switch S that triggers a step voltage for only a small time interval. 2) S is connected to a free non-powered transmission line pair with a resistor load at other end. 3) When S is triggered (on then off), a step signal will travel along wire and will be detected at the load.

The wires need not be initially powered for the signal to be transmitted.

Answer 1

This is the Very Large Array telescope in New Mexico: (Image source: nasa.gov)

This telescope works by receiving radio signals from distant objects from multiple small antennas, then combining these signals to image the objects emitting those signals.

Since the antenna elements are quite far apart, to combine the signals means they must be carried from the elements to some common location. (Alternately, they might be digitized at each antenna element, but then a common timing reference must be distributed to all the antennas) If the phase delay due to the interconnecting cables between the antennas was not predictable, the entire scheme would not work.

So the experimental evidence for the correctness of the telegraphers equations is that this telescope (and numerous other radio devices built over the last 150 years) can be made to work.