-

Jump to content



Sign up for a free account!

Signing up for an account is fast and free. As a member you can join in the conversation, enter contests and you won't get the popup ads that guests get. Click here to create your free account.

Photo
- - - - -

testing DIY cables


This topic has been archived. This means that you cannot reply to this topic.
10 replies to this topic

#1 of 11 kurtZoom

kurtZoom

    Stunt Coordinator

  • 62 posts
  • Join Date: Jan 24 2005

Posted June 30 2006 - 01:52 AM

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.e...er/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.
Growing old is mandatory
Growing up is optional

#2 of 11 Marc L

Marc L

    Stunt Coordinator

  • 93 posts
  • Join Date: Feb 08 2006

Posted June 30 2006 - 10:13 AM

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 of 11 Bob McElfresh

Bob McElfresh

    Producer

  • 5,183 posts
  • Join Date: May 22 1999

Posted June 30 2006 - 05:16 PM

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! Posted Image

#4 of 11 kurtZoom

kurtZoom

    Stunt Coordinator

  • 62 posts
  • Join Date: Jan 24 2005

Posted July 01 2006 - 04:18 AM

thanks guys...I'm ready to start
Growing old is mandatory
Growing up is optional

#5 of 11 Alfonso_M

Alfonso_M

    Second Unit

  • 396 posts
  • Join Date: Sep 25 2000

Posted July 02 2006 - 02:28 PM

Quote:
Originally Posted by kurtZoom
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?


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-OKPosted Image

#6 of 11 kurtZoom

kurtZoom

    Stunt Coordinator

  • 62 posts
  • Join Date: Jan 24 2005

Posted July 02 2006 - 11:59 PM

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?
Growing old is mandatory
Growing up is optional

#7 of 11 Alfonso_M

Alfonso_M

    Second Unit

  • 396 posts
  • Join Date: Sep 25 2000

Posted July 03 2006 - 05:26 AM

Quote:
Originally Posted by kurtZoom
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?

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 Posted ImagePosted Image

#8 of 11 KurtBJC

KurtBJC

    Agent

  • 47 posts
  • Join Date: Jun 22 2003

Posted July 03 2006 - 01:32 PM

Quote:
Originally Posted by kurtZoom
...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?

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 of 11 Bob McElfresh

Bob McElfresh

    Producer

  • 5,183 posts
  • Join Date: May 22 1999

Posted July 03 2006 - 04:42 PM

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. Posted Image

#10 of 11 KurtBJC

KurtBJC

    Agent

  • 47 posts
  • Join Date: Jun 22 2003

Posted July 03 2006 - 05:23 PM

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 of 11 kurtZoom

kurtZoom

    Stunt Coordinator

  • 62 posts
  • Join Date: Jan 24 2005

Posted July 04 2006 - 01:16 AM

Quote:
Originally Posted by KurtBJC
Ach! That's what I get for not reading closely....yes, of course one should get a 75 ohm resistance reading on those terminators.
That makes two of us.
Thanks guys.
Growing old is mandatory
Growing up is optional


Back to Members' Theaters, HT Projects, Remotes, Seating, Accessories & Lighting



Forum Nav Content I Follow