> From what I understand, it moves all the energy to a single
> sideband..so you have to slightly detune it to get the most
> power.
>
Powerside is very effective for AM directional stations that "lose" the carrier in nulls. It is very handy also if your antenna is not "flat."
Now, in layman terms! If you have a directional AM station there will be areas where the signal is strong in some directions and areas where the signal will be weak in some directions. Sometimes, in the weak areas, the main carrier "goes away" and only the sideband energy is left. This can cause severe distortion in many AM receivers.
The same thing might happen to even a non directional station. Often, if powerlines near the transmitter site re-radiate the stations signal, the signals arrive out of phase and cancellation of the carrier occurs. Again, distortion in the receiver occurs.
When matching the transmitter to the antenna, the "match" must be good at the carrier frequency to efficiently transfer the power to the antenna. The antenna must also offer a linear impedance (or "match") to the sidebands....above carrier and below carrier. When the above carrier "match" and below carrier "match" are not equal, then distortion occurs in the receiver and the transmitter does not operate efficiently.
Powerside can be used to operate with sidebands above, or below carrier. It effectively becomes a single sideband system. Your radio does not care if both sidebands are there or not.
See last month's Radio World (radioworldonline.com) for an article by Jerry Smith addressing Powerside. Jerry has always loved it and swears by it.
But you won't find it on many stations.....you see it in racks from time to time but most just don't run it!