[BC] Computer Noise

[Lewis Munn]

Stanley,
   
  What is the noise?  HGunm?  High fequency hash?  Tones?  Clicks?  Does it happen when the computer isnfirstnturned opn,when it is booted, only when it is processing something?  Does the noise go away if you shut off the monitor?  shut off the audio?
   
  What equipment gets the noise?  Receivers?  Audio preamps?  Distribution amplfiers?  Yur own monitor amplifier?  Console?  Tape decks?
   
  What wiring runs near the computer?  What equipment is the computer near?  Do yuo use a line noise supressor,like ISOBAR, on the computer?
   
  Radiated noise can usually be detected with a portablearadio, and the source determined by finding where itn is loudest...having a small portablerather than a boom bix helps in sniffing.
   
  I would in general be sure ALL the equipment is grounded solidly to at let a 2" copper strap,hich itself gos to a good station groundf AND the AC ground at the entrance.
   
  Ground the computer case to this good RF and Noise ground also.
   
  Another thing to watch is that you are not having the computer onnone leg of the 3-phase and the equipment that is getting noise on another, with a connection between.
  A 600-600 isolation transformer, or an isolated DA can cure that particular problem.  I have used the RU4-A  as a 1-1 isolation by NOT carrying a common ground thru.  Not ideal, but works and is relatively cheap.
   
  Find what kind of noise it is, where it is getting in, see if solid, really solid, grounding helps (can't hurt!!), and look at isolation devices.  And AC noise filter units.
   
  Good luck, and keep us informed about what you find, waht you try, what you find helps or works, and in the end, what cure was obtained.
   
  Watch for brushes on some DC motors.  And broken or disconnected shielding on audio lines
   
  AC line noise supressors on the devices getting the noise can be effective also, again if well grounded.  
   
  In general, linear regulated power supplies are much quieter than switch mode supplies, but are also more expensive and bulkier and somewhat less efficient.  But I have worked in stations with many computers all over,and never had a noise problem
  that was not either lack of grounding to the station low-impedance ground system, or most of the time a problem with getting equipment on two different phases of the AC feed.
   
  One other thought...if you are in a STRONG RF field, it could be RFI into the computer...which means excellent grounding of the case, and RFI supression on ALL lines in and out...and possibly screening the plastic areas.  Determine what transmitter is causing the interference, and supress all leads in and out for that frequency band.  CorCom makes some supressors for some applications; and others can be home-brewed with reference to the handbooks.
   
  Looey Munn
  Roundup, MT

Stanley Adams <stanleybadams at yahoo.com> wrote:
  Guys I have a computer that really kicks a lot of trash out 
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