Reducing Video Noise

DXers still chase analog TV signals that originate outside the U.S. Callsigns can be difficult to discern due to noise, multipath, and co-channel interference. A simple way to enhance a static video image might be to photograph the screen using a long exposure time. The amplitude of additive noise and uncorrelated interference should decrease as the square root of exposure time. To test the idea, I connected a monochrome video camera to an RF modulator, attenuated the output 45 dB, and connected it to my TV.

Frozen TV frame. This image looks much noisier than did continuous live video. Evidently the eye and brain do a fair amount of integration all by themselves.

Continuous video. 1/20 sec at f/4.2. This looks a little noisier than did live video.

1 sec at f/18. This looks much cleaner than live. S/N should be 20log(√20) = 13 dB better than at 1/20 sec.


June 29, 201388108 MHz