Richard Clark wrote:
"---the distance was far enough to observe the effects of SWR - in
exactly the same manner we observe them at HF or VHF etc."

Yes, that was anticipated.

The wavelength is a little less than 186,000 miles per second divided by
60 cycles per second, or 3100 miles per cycle approximately. The
reduction in wavelength is due to the velocity factor of the
transmission line. Construction determines the velocity factor.

The phase delay ib transmission over the actual distance between Hoover
Dam near Las Vegas and Los Angeles is only a few degrees. For example, a
60 Hz transmission line slectrical length of 310 miles would be 1/10
wavelength or about 36 degrees. Surely noticible but not crippling.

Now, many high-voltage transmission lines are transporting d-c. The rule
of thumb is that you need a kilovolt per mile of trangmission line
length to get efficiency. So, hundreds of miles require hundreds of KV.
At these voltages, the difference between rms and peak voltage becomes
important. RMS = DC. Now, conveersion from a-c to d-c and back again is
fairly easy and efficient. So, we have HV, DC power transmission. Tesla
had the first laugh. Now, maybe Edison has the last laugh after a
hundred years of development.

Best regards, Richard Harrison, KB5WZI