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#1
Posted to alt.electronics
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build a video cable
Depending on the price I may want to build my own coax video cable to connect a "standard" tv to dvd player (and other things). The video jack is an RCA. It's marked with a yellow band (impedance spec?) What coax cable type is best for building this type of cable? Thanks |
#2
Posted to alt.electronics
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build a video cable
On 2005-12-26, werwer wrote:
Depending on the price I may want to build my own coax video cable to connect a "standard" tv to dvd player (and other things). The video jack is an RCA. It's marked with a yellow band (impedance spec?) What coax cable type is best for building this type of cable? yellow is the usual colour code for composite video. like red for the right audio and white for the left, black for mono etc... composite video signals are 75 ohm, for long runs a 75 ohm coaxial cable is a good idea. for shorter runs cheap shielded audio cables work fine. Bye. Jasen |
#3
Posted to alt.electronics
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build a video cable
On 26 Dec 2005 09:58:31 -0800, "werwer" wrote:
Depending on the price I may want to build my own coax video cable to connect a "standard" tv to dvd player (and other things). The video jack is an RCA. It's marked with a yellow band (impedance spec?) What coax cable type is best for building this type of cable? Thanks An ordinary twisted pair of wires may be just fine. With video, if you mismatch the cable and connectors you can see the result. You see a "ghost," (outlines are most noticeable as being offset from the original . . . horizontally) The "type F" connector is made for 75 ohm video. The RCA connector isn't, it is made for audio. It does not match 75 ohms. The connector and cable impedance is determined by the diameter of the inside conductor and the shield. Type "F" was developed for video (actually, is was around for a lot longer)- the RCA was only intended for audio where impedance of the connector isn't important. But . . . I have a few surveillance cameras with 75 ohm outputs feeding a receiver about 100 feet away (with RCA's) , and am using cat3 UTP. Category Three Unshielded Twisted Pair . . . It has a nominal impedance of 100 ohms and makes no (visible) difference to my 75 ohm input and output. My cable is buried in 8+ inches of wet soil with no outside coating or conduit, just the vinyl jacket. From my experiments - don't sweat the impedance. Try it, you may like it. If you want to buy a cable with RCA connectors and that works for you, do it. Try it first. Try it with a simple twisted pair of wires, or buy a cable with connectors that mate with your equipment, or just buy the cable you need. Nine times out of a ka zillion the signal source has a low impedance (lower than 75 ohms) feeding an input that has a much higher impedance, like in the millions. Match the impedance when you are concerned about absolute fidelity. Botch it completely and you'd still have better resolution than the ATC or "Convenience Mart" camera's you see on TV. If you need to send lots of bandwidth over lots of cable for lots of subscribers . . . then signal strength and impedance matter much more. -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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