Originally Posted by Winston_1:
“Another error is that Power equals volts times amps times power factor.”
In this instance, where you are talking about the unwanted radiation of electrical signals through a cable, power factor is an irrelevance.
Even if it were relevant, power factor is going to have an attenuating effect not an amplifying one.
Originally Posted by Winston_1:
“Taking the error into account means up to 4 watts is radiated. No wonder there is so much interference. PLT has been shown to cause interference up to 500 metres. 4 watts into a decent aerial can go much further. Some TV relay transmitters are less than 4 watts.”
You are right, 4 watts in to an aerial is a reasonable output, except the four watts isn't going in to an aerial, it is going in to a wire. A wire that is of indeterminate length compared to the frequencies being radiated, which would limit the amount actually radiated in the first place as there would be attenuation because of standing waves, plus the radiated frequencies wouldn't be radiating in to free space as there would be attenuation through the building walls.
So the total radiated power in my hypothetical example in to free space outside of the house would be considerably less than 4 Watts, but the interference received at ant aerial would be even less than that.