Total posts : 45366
My take on the sparse information in the LPB Neutral Loading Option shown in: http://utopianetwork.home.comcast.net/carrier/ccneut.pdf is that you just plug the transmitter into a wall outlet and it will feed the signal to the neutral terminal. The transmitter ground is shown as being separate. The neutral terminal on an outlet is connected directly to the building ground rod back at the breaker box. So the load resistance will be the difference between where the transmitter is grounded and the building service entrance ground, probably just a few ohms. This is essentially a direct short. However, if the outlet is a significant distance from the service entrance, there will be an unknown amount of RF impedance, depending on a lot of factors. For signal strenth, the longer the run, the better. Not a pretty setup.
Old time full blown carrier current campus systems distributed the RF by coax to each building. High current RF inductors were inserted in series between the power feed to the building and the internal wiring. The RF from the coax was then coupled to the hot legs on the internal wiring side of the inductors. This is best for efficiency and for preventing the signal from radiating from the overhead power lines. But, this is still extremely inefficient because the signal is attenuated by the internal building wiring hot lead to ground capacitance. The transmitter needed to run at fairly high power to overcome the losses. And, talk about hum!