I don't think it is legal to transmit on those frequencies, thats what the stations pay big bucks for.

Radio stations pay big bucks to broadcast on the FM frequencies, and yet they make FM Transmitters for your car. Why wouldn't DTV be the same?

Thats a good point, I didn't think of that. The FCC did make some allowance for low power FM transmitters, probably because they couldn't control it anyway. I see some people selling similar low power TV transmitters, but I don't know why it isn't more common. Since it is more complex than the FM transmitters and more of a risk, I wonder if the lack of FCC regs has stopped it in the US.

Low power FM refers to a specific class of licenses[1] and not the little radio dongles.

[1] http://www.fcc.gov/encyclopedia/low-power-fm-broadcast-radio...

That won't help you broadcast to a projector. Working with an HDMI connector, you solve the problem for both TVs and projectors.

Because you can't broadcast in frequencies that overlap with the actual TV signals, which is what that actually pick up?