[ICOM] Icom, Grounds and Mikes

[Jerry Keller]

Dave... I have all my equipment chassis-grounded to a single copper bus that connects directly to a single point ground (large copper plate in a box) at the entry point to the shack. All of the equipment AC power cords are three-prong. Every coax line is grounded at the SPG and at the feedpoint. The SPG is bonded to a peripheral ground line that encircles the house and is bonded to the AC service ground. There are ground rods every 15 - 20 feet along the peripheral ground. The vertical and tower grounds are all bonded to the SPG. Seems to me this combines all power and RF grounds into a single common system with none of those "audio loops" you mention. Would you agree? If not, where do you see a problem?

Any critical help or suggestions appreciated, 73 Jerry K3BZ
  ----- Original Message ----- 
  From: David J. Ring, Jr. 
  To: ICOM Reflector 
  Sent: Friday, July 30, 2004 1:06 AM
  Subject: Re: [ICOM] Icom, Grounds and Mikes


  Jerry,

  Ground loops (in audio) are caused by multiple grounding paths (audio
  ground).

  Sometimes a tape recorder (or some other auxilliary equipment such as
  equalizer or preamps) which using a grounded 3 pin USA electrical plug is
  plugged into a sound board, or recording mixer and it will cause a ground
  loop, but putting a 3 to 2 electrical adapter (and NOT using the ground pin
  to ground the adapter to the wall outlet) will solve this problem.  Now the
  tape recorder will be connected to the recording mixer only by the audio
  cable ground - and NOT by the electrical ground.  This eliminates the ground
  loop.

  Many audio engineers and audio recordists keep a few 3-to-2 adapters in
  their tool box just for this purpose.

  In ham radio, the ground loop problem can be solved by having only ONE path
  for ground.

  Western Electric (part of AT&T at one time) used to engineer a common ground
  at their medium wave radiotelephone stations at the antenna ground screen
  common point.  All the antennas ground screens and radial common points were
  lead to this common point, also the electrical local ground was at this
  point (green wire of AC wiring).

  Coaxial cables leading to transmitters grounded those transmitters at the
  Antenna Common Ground Screen Point.
  Likewise the receivers were connected to this ground via the coaxial cables.

  I know that there have been A.C. ground loops also.  Some of the symptoms
  were R.F. on the 120 VAC line.  I believe a similar cure for this was to
  install a single point of R.F. ground at the power pole line drop.  (A
  filter at the power company pole where it fed the radio station).  These
  A.C. ground loops would introduce regenerative distortion to r.f.
  transmitters.

  73

  David Ring, N1EA


  ----- Original Message ----- 
  From: "Jerry Keller" <k3bz at arrl.net>
  To: "ICOM Reflector" <icom at mailman.qth.net>
  Sent: Thursday, July 29, 2004 11:22 PM
  Subject: Re: [ICOM] Icom, Grounds and Mikes


  Bill.... I have a similar problem here, and I'll bet there's lots of us out
  here...so please let us all know what you figure out for reconnecting the
  station ground set-up. 73, Jerry K3BZ



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