shielding cable

Discussion in 'DIY Discussion' started by bottleneck, Aug 4, 2003.

  1. bottleneck

    bottleneck talks a load of rubbish

    Joined:
    Jun 19, 2003
    Messages:
    6,766
    Likes Received:
    0
    Location:
    bucks
    Someone on the forum recently said -

    that an interconnect/cable per se which has shielding THAT IS NOT EARTHED is in fact acting as an ariel to increased RFI.

    Is this true?

    If it is true, should a lead be soldered from the earth wire of an interconnect to the shielding?

    Should this be done at both ends - does it matter which end?

    I ask this because I have unshielded interconnects that I wish to shield, and my system is prone to RFI..

    thanks in advance
    Chris
     
    bottleneck, Aug 4, 2003
    #1
    1. Advertisements

  2. bottleneck

    zanash

    Joined:
    Jun 20, 2003
    Messages:
    3,826
    Likes Received:
    0
    Location:
    Notts.
    A bit of cable theory or not.

    The signal wire well we know that goes to the central pin of the RCA easy.
    The return or ground can be a coaxial sheath that surronds the signal wire, or it could be a single wire. Its common to twist the two together as this help rejection of grunge. These two twisted pairs can have a braided shield run up the outside of the pair, this then is the nub of your question.

    The shield may be grounded at both ends, but this would allow the shield to be used as the return, so attaching at one end allows any intercepted grunge to be rapidly earth to the connected end. Its common to orientate the sheild connected end to the source component feeding the grunge away from the signal direction.This may acount for the dirrectionality of some cables. This cable is also known as Pseudo balanced cable, partialy emulating the effect of an XLR.

    To shield a cable I would use adhesive copper foil and wrap so that each wrap 50%over laps the last wrap. You can add a small cap in pico farrad range but I rarely bother. Its intresting you should ask this as this afternoon I was medling with a cassette deck and wrapping all the cable bundles in foil and star earthing them. Did it make a difference well with the Schottky diodes its been quite a suprise, noise floor has drop conciderably.
     
    zanash, Aug 4, 2003
    #2
    1. Advertisements

  3. bottleneck

    bottleneck talks a load of rubbish

    Joined:
    Jun 19, 2003
    Messages:
    6,766
    Likes Received:
    0
    Location:
    bucks
    Hi Pete!

    Thats helpful, thankyou.

    Valves can be noisy, and IME the more valve based components youve got the more the smallest bit of noise can be cumulative...

    I have some sticky foil that hippy gave me for the purpose, can you solder onto this stuff I wonder, if not how do you connect it to the earth - just jam them together?!?!

    Thanks! :D


    Chris
     
    bottleneck, Aug 4, 2003
    #3
  4. bottleneck

    themadhippy seen it done it smokin it

    Joined:
    Jun 19, 2003
    Messages:
    1,118
    Likes Received:
    1
    Location:
    by the cross
    you can but you need a powerfull iron (or mini blow torch) and some extra flux helps
     
    themadhippy, Aug 4, 2003
    #4
  5. bottleneck

    bottleneck talks a load of rubbish

    Joined:
    Jun 19, 2003
    Messages:
    6,766
    Likes Received:
    0
    Location:
    bucks
    thanks hippy!

    is that whats best BTW? or is there another way to meld the two together?


    :D
    Chris
     
    bottleneck, Aug 5, 2003
    #5
  6. bottleneck

    zanash

    Joined:
    Jun 20, 2003
    Messages:
    3,826
    Likes Received:
    0
    Location:
    Notts.
    The foil I hve just needs to be touched with the tinned Iron, and it is very easy to add a drain wire. The alternative to foil is to wrap a wire around the cable in a spiral connected at one end. This will provide a small ammount of shielding, It really depends on the level you need.
     
    zanash, Aug 5, 2003
    #6
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.