testing DIY cables

Discussion in 'Accessories, Cables, and Remotes' started by kurtZoom, Jun 30, 2006.

  1. kurtZoom

    kurtZoom Stunt Coordinator

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    I've searched this forum and came up empty on what I'm looking for. I purchased a used set of tools and all my materials to follow the recipe provided in
    http://www.bus.ucf.edu/cwhite/theater/DIYCable.htm
    to make DIY cables. My Outlaw 990/7125, and Oppo 971 will be delivered today...so tonight I will be making cables.

    I want to test each cable as I make them. I'm assuming I can use a volt ohm meter just to make sure the cables are at least connected correctly.

    Is it simply checking conductivity between the ends and between the ends and the outer part? or is there more to it than that?

    Any other last minute recommendations/hints or suggestions?

    I'm using both the L-5CFB and the LV-77S wire. I have the proper RCA ends for each wire. I'm also making some with FP-C5F ends.
     
  2. Marc L

    Marc L Stunt Coordinator

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    as long as you make sure that there is no short between the outer ring and the center conductor, you should be fine. check it before and after you crimp the connector on...this way you can troubleshoot problems as you go.
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    Some advice:

    cut some spare coax and practice stripping the ends. Your first strip will be bad, but after 3-5 the quality will improve.

    When you are ready to make your real cables - cut the coax to as close to exactly the same length for all 3 wires. Then strip all 6 ends before you attach your first plug. This way if you mess up, you simply trim the 3 ends on the side you messed up to identical length and start again.

    Since you have bought the coax, plugs and the crimp die that are all designed to work together - they are almost always perfect. The only variable is the stripping which is why I suggested you practice a bit.

    It's actually a lot of fun to make your own cables so congrats! [​IMG]
     
  4. kurtZoom

    kurtZoom Stunt Coordinator

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    thanks guys...I'm ready to start
     
  5. Alfonso_M

    Alfonso_M Second Unit

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    another more elavorate but sure testing method is to use a 75 ohm "F" type terminator attached to a F--->RCA adapter, testing between the center pin to the connector body should read pretty close to 75 ohm, if there is a short the reading will fluctuate wildly. I made my cables using this same materials a few years back and double checked many times before hooking up to the expensive equipment. they were all A-OK[​IMG]
     
  6. kurtZoom

    kurtZoom Stunt Coordinator

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    thanks Alfonso...I was wondering...I was under the impression that the RCA ends were also "75 ohm"...shouldn't I get a 75 ohm reading on those ends as well? or is it just the F type?
     
  7. Alfonso_M

    Alfonso_M Second Unit

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    yes, the RCA patches also, (reading is never exactly 75 ohms as the longer the patch the more loss), that's why I mentioned the (female) F --> to female RCA adapter, this way you can test your Canare RCA cables, "F" 75 ohm terminators are easy to find as they are used to plug up unsued CableTV/Sat RG6 run's spliters, I've never seen RCA terminators although they may exist, The Rat Shack carries all this (at least they did a few years back) , but I'm sure online stores probably will give you a better deal.

    in the old days of Computer Network Cabling this inexpensive method was used to trouble shoot "open" lines and shorts ( we also had expensive testers), although the wire used was RG58/59 with BNC plugs which requires 50 ohms, before that there was another RG cable used (?) that was 90 OHMs. wow! this is ancient networking history now [​IMG][​IMG]
     
  8. KurtBJC

    KurtBJC Agent

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    Actually, with a VOM you shouldn't get 75 ohms on anything. The "75 ohms" in "75 ohm cable" or "75 ohm connector" isn't resistance; it's characteristic impedance, which you can't measure with a VOM. You should simply be testing for continuity of center conductor and shield, and non-shorting of center conductor to shield. Now, if you have a sufficiently long (really, really long) cable, your center conductor might measure 75 ohms....but that wouldn't have anything to do with impedance.
     
  9. Bob McElfresh

    Bob McElfresh Producer

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    Alfonzo was talking about those small termination caps you put on the un-used parts of a CATV splitter. They have a small 75 ohm resistor in the cap and it screws on.

    He was suggesting creating a 'termination cap' for the end of an RCA plug, then measuring the resistance from the other end. The VOM should 'see' the 75 ohms of the cap and not flicker (which would indicate a short or some braid touching where it should not.)

    A rather clever idea Alfonso. [​IMG]
     
  10. KurtBJC

    KurtBJC Agent

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    Ach! That's what I get for not reading closely....yes, of course one should get a 75 ohm resistance reading on those terminators.
     
  11. kurtZoom

    kurtZoom Stunt Coordinator

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    That makes two of us.
    Thanks guys.
     

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