I have also discovered that the "wall-wart" a.k.a. power supply for the rc-dt09 caused interference with a nearby FM radio.
I was able to greatly reduce the interference by wrapping the d.c. cord coming out of the power supply around two sides of a snap-together RFI toroid choke. (as pictured in the diagram)
I put the choke as close to the power supply as possible, meaning the cord comes right out from the p.s. and into the choke.
Another reason for reducing the RFI produced by the wall-wart, is that it may interfere with the DTV signal. I noticed a slight improvement on the signal strength of the weaker stations I mentioned earlier. (signal strenth was at bad, now inbetween bad and good)
This resulted in less pixellation/break up.
Power supply RFI might be an issue for other converter boxes as well.