[ICOM] Icom, Grounds and Mikes

[David J. Ring, Jr.]

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