Total posts : 45366
I think radio8z has your answer. A coil loaded antenna will produce the highest output. This alone would not be enough except that you can create a pseudo carrier-current system by NOT grounding your transmitter. As long as there are no RF chokes in the path to your power feed, a significant amount of RF will feed through to the building wiring. This may be enough to enable others in your building to receive a strong signal. This is true for the SSTRAN transmitter because the wall adapter is just an AC transformer, which has a low pass-though impedance for RF. Other types of power supplies may not have a low impedance for RF.
Leaky coax is only good for a small range along the length of the coax. You would need to run leaky coax all through your building for it to be effective.