Keeping your monitor out of blue / lost signal screen

I have a old laptop 15.4" LCD screen that i converted to a monitor with a **broken link removed**. I'm planning to use this screen as a screen to view a signal that i recive from a wirless transmitter. But when my signal is to far from the source i loose the image and my screen goes in signal lost or blue screen until i recive a new signal. But every time I get the signal back theres a second delay until i get the image back becouse the monitor is slow i guess.

Now im looking for a solution to trick the signal that the monitor gets with another noise signal. So when i lose the signal the monitor wil get the noise and dont lose go in no signal mode...

Can you guys point me in the right direction with a circuit or something?

The signal i receive is a video stream of a live camera NTSC: 510(H)*492(V) or PAL: 500(H)*582(V). (I would rather have it working with PAL then NTSC)

I have a basic understanding of electronics/ circuits but I have totally no knowledge about video data.

Thx