Coaxial Switch Using Arduino and Multiplexers

arduinovideo

Hi maybe someone can help me here, basically I am trying to build a computer controlled coaxial switch. I am using a regular Integrated circuit multiplexer to handle which channel is patched to output. So basically I have:

              (8 X Coaxial Inputs)
              I I I I I I I I

microcontroller —-> | Multiplexer | ————— I (1 X Coaxial Output)

The idea is so that I can use a computer to control which of my 8 video feeds that I can watch. I thought that because the connections are straight through I wouldn't have to worry about attenuation as much, but I tried a sample setup using a breadboard and I can barely see the picture. Any ideas as to how I can make it work?

I am currently using a breadboard with all the components I listed Plus some small gauge cables (so that they fit on the bread board)

UPDATE:
This is what My setup Looks like http://img6.imageshack.us/img6/6320/49195403.png
the MUX is a UTC 4051 Data Sheet is Here http://alldatasheet.com/datasheet-pdf/pdf/173652/UTC/4051.html

Best Answer

I bet you didn't buffer the output.

If you tried to direct drive your 75ohm load, you would discover a lot of attenuation from the 250ohm switch resistance.

Use 10K load or so and buffer the output with a 75ohm line driver or whatever you can buffer with 10MHz BW or so. Consider how critical your levels need to be and matched source impedance to 75 ohm. Ideally everything sourced to your monitor is 75ohm for NTSC composite video.

I hope that works and my intuition is correct.

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