At 100MHz, I'd be more inclined to feed RF between Neutral(white wire) and GND (green wire) instead of L1 (black wire) to Neutral. Lots of appliances have internal filter capacitors between L1 and Neutral, as well resistive loads, which would tend to short the 100MHz signal, maybe even plugged into the same duplex outlet only inches away.
Between Neutral and GND, there is also a short circuit, but it is back at the main distribution panel, many wavelengths (at 100MHz) away from where the transmitter is likely to be plugged in... Also, there is no voltage between Neutral and GND.