Active Video Signal Distribution - Why? Contrary to analog audio technology, image signals require the transmission of significantly higher signal frequencies. The transmission of TV images (PAL, 625 lines, 50 half images) requires a transmission band width of > 6 MHz (comparison: audio band width 20 kHz). Coaxial cables are used for image transmission. The conditions for power adaptation apply, based on the technical principles of high frequency technology. This means that the video source has an impedance of 75 Ohm.Video inputs have an input impedance of 75 Ohm. For Video Technology: Performance adaptation Source impedance = Load impedance Thus: Contrary to audio technologies, the option to connect two units up to the same video source is not available here. The result is that active components are required for the distribution of one video source to several users. And what about the Loop Outputs? Many video technology units, e.g. monitors, high quality VTR machines, and signal processors have loop outputs parallel to the output. Here the terminating resistance on the input can be deactivated. The video signal can be looped on these units, but the chain has to be completed with 75 Ohm on the last unit. The cable lengths should also be taken into consideration. The signal gets dampened somewhat on each BNC-connection, so that in the worst case the level will be insufficient on the last unit. This cable also is not free of return effects. If the line is interrupted due to an operating error, service work being performed, or a short circuit the signal will be missing on all units. That is why Distribution Amps are required The diagram shows a video distributor (FBAS) with one input and 4 outputs. Each output drives one video line at an adaptation suitable to the norm, free of return effects. This enables star-shaped distribution and minimizes performance losses. Compensation of Performance Losses The longer the path for the video signal, the higher the losses on the line. The resistance parameters on the line and the cable capacity create a low pass. The upper frequency decreases with each meter. The useful signal level also decreases. That is why an intensifier is needed to increase the level and to optimize the frequency response starting at a cable length of approx. 50 m. Thus the image is noise free and the color segments remain unaffected. But there are limitations, starting at approx. 100 m cable length one should think about other types of transmission, e.g. twisted pair. Perform. compensatation after 50 m; example: Analog Video Formats >>> For RGB (VGA/XGA) >>> Converters >>> Signal generators >>> Twisted Pair Transmission >>> Seamless Switcher for Conference Applications >>>