use of automatic level control circuit in RF

what is use of rf detector mainly in ALC
how can i Select it
how to see specification for it



what is the main spec need to see in video amplifier

You do not want ALC in a video amplifier because it will cause everything to have the same contrast. A video amplifier must have plenty of dynamic range.

A good video ALC circuit only measures the sync amplitude and normalizes it. That (if the video is any good) lets it adapt to different levels without being influenced by the picture content.

Brian.

Ah with old fashioned analogue, the ALC was referenced to the ITS bar amplitude, kept it at the right level and the black level was clamped to earth.
Frank

What would cause the level of video including the sync pulses to vary? Not if it comes from a camera. If it comes from a radio then the radio should have RF ALC not video ALC.

We used video correctors on long multi hop RBL links over sea paths. Part of the requirement was to offset the effect of demodulating/ remodulating 4 times, the other was because of differential fading, the modulation depth increases. So if the receiver keeps the envelope at a constant level, the peak video is seen to rise. Also offsets dodgy post office lines between the studios and the transmitters!
Frank