[ICOM] Icom, Grounds and Mikes

[David J. Ring, Jr.]

The traditional "fix" is to have ONE ground point, eliminating common
grounding paths.

In your set-up, you have at least TWO and probably THREE paths for
grounding:

1)    A.C. mains powered equipment to ground via the green wire to the A.C.
power line service line ground.
2)    Via coaxial cable to the SPG, but also from the tower there is another
path, down the tower to the SPG -
3)    From the electrical service entry box to the SPG.

If you do develop any problems, I'd take off the equipment grounds and let
the equipment ground via the coaxial cable.

With all the connections, you have done a lot of work, but also should you
have any problems, you can always disconnect any of the individual units.

If it works, don't mess with it.  You probably have an excellent grounding
system - but there are certainly different modes that "could" exist.
Unfortunately there are different impedances for r.f., audio, and power
grounds - which make the problem even more difficult - but you've done one
important thing - you probably have a very very low loss ground and probably
a very low impedance r.f. ground.

73

David N1EA

----- Original Message ----- 
From: "Jerry Keller" <k3bz at arrl.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Friday, July 30, 2004 11:07 AM
Subject: Re: [ICOM] Icom, Grounds and Mikes


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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Icom Users Net: Sundays, 1700Z, 14.316 MHz
Icom FAQ: http://www.qsl.net/icom/