To receive this signal on any TV set you need a TV modulator, as these circuits (including PIC-based with 2-resistor D/A from your last post) generate baseband video signal ..
The rason why some TVs may pick-up 'something' is that this signal has a lot of harmonics (as any square wave has) but the high-order harmonics are very, very weak and you need a sneaky path (which ground-connection just happens to provide) to get them to the TV's tuner ..
You can still use this signal by connecting it to TVs' AV-input (usually with RCA connectors) and selecting LINE (or AV) input ..
Regards,
IanP