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This type of hum suppression transformers have found their way to the professional video application (rental companies) and comouter video applivations (computer to video projector connections). This kind of devices are capable of passing the signals from DC to tens of MHz without problems. ![]() Those special transformers act like a common mode coils, which stop the annoying ground loop currents on the shield of the coaxial calbe, but provide a straight path for the signal inside the cable. There are passive hum suppressor transformers which will very effectively remove the hum from the video signal (typically around 40 dB hum level reduction), but do not effect the video signal otherwise. Ground loop elemination does not always ask for a complete isolation of the grounds. There are some this type of isolation devices on the market and some special video distribution amplifiers have this kind of option built in. Differential inputs are also used in applications where a video signal is transmitted through twisted pair wiring (some CCTV applications which use twisted pair interfacing equipments).Įlectro-optical isolation works well in applications where complete electrical isolation is necessary. Differential input with floating ground works nicely for small ground potential differences and this approach is used in some professiona video equipments (some video projectors I have seen have had differential inputs and option to disconnect input ground connection). Those both technologies are usable in real world situations. Isolating video signal needs typically active technology which involves electro-optical isolation or differential amplifier with a floating ground on the input connector. Isolating video signal is more complicated than isolating audio or antenna signals, because the DC level of the video signal is important and video signals have very high frequency spectrum (normal composite video can have bandwidth from 50 Hz to 6 Mhz). Ground loop isolation in video lines Ground Loop Isolator GB0001
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