I've been attempting to recreate the effect of an old NTSC television broadcast lately with the use of DVDs. The DVD-Video spec allows for up to 720 x 480 pixels at a display rate of 29.97 frames per second, interlaced.
My DVD player is outputting composite video to an RF modulator which is then connected to my TV and the signal is demodulated by the receiver, effectively simulating the NTSC transmission model.
What I'm wondering is if RF modulators output NTSC System M spec video for everything you feed it, allowing for a maximum video bandwidth of 4.2 MHz or about 330 lines of horizontal resolution (440 x 486 from a digital perspective), or if it's converting the composite video signal to RF however it sees fit and the resulting image will look more like 540 line DVD?
Any help would be greatly appreciated.
Best Answer
That would depend on the specific modulator, but RF signal output is just basically the same composite video it gets but modulated to RF.
So the RF output will be NTSC-M if the baseband CVBS that is sent to modulator is also NTSC-M compliant, and that the modulator modulates it in NTSC-M compliant way.
Some sources can/may output non-broadcast compliant CVBS baseband signals, because the output is meant to be connected to a TV or other equipment, and not meant to be transmitted over RF in a compliant fashion. The modulator can and will most likely limit the bandwidth to fit the signal to the RF channel, but it will still modulate whatever compliant or non-compliant signal it gets in.