[ICOM] Icom, Grounds and Mikes

[George, W5YR]

At the risk of inviting a deluge of dissent, and with apologies to Jim ahead
of time, it is my opinion that the worst advice ever given about an amateur
radio station is to ground everything and have a "good r-f station ground."
As William found out, "grounding" each piece of gear somehow to something
called a ground is some of the worst system engineering one can imagine.

I think that all this comes from the mindset - completely in error - that
"ground" is some sort of magic infinite sink for any and all signals that
are unwanted. So just connect everything to this "ground" and all the bad
stuff is dumped and all problems are gone. I never have been able to
understand how that wire going to this "ground" is able to know what is the
bad stuff and pass it and yet not dump the good stuff along with it.

I have seen many instances where "grounding" caused more problems than it
cured. Your equipment is a-c safety grounded by that green wire in the power
cord. Interconnecting cables contain whatever signal commons - not
"grounds"! - are needed. Anything else is almost always unneeded and just an
invitation to trouble of one sort or another.

There are some instances where tying two pieces of gear together - chassis
to chassis, for example - is the proper thing to do. There are many more
instances where it is the wrong thing to do.

If you are having any station problems, start by removing or eliminating all
external "ground" connections between equipment and to whatever you might be
using for that magic "good r-f station ground." Then go to work on the
antenna system so that (a) your station equipment is no longer part of the
antenna system and there will be no r-f in the station; and (b) eliminate
coax outer-braid currents - common-mode currents - by proper use of baluns
on all coax lines. Yes, Virginia, every coax line - I know that you can get
away with leaving them off sometimes but not a good idea.

"Ground loop" problems involving a-c service have to be dealt with one at a
time. Solutions are not always self-evident. Sometimes you get lucky as
William did by simply removing all interconnecting ground connections.

Finally interconnections between the radio world, the computer world and the
audio world are usually best handled by means of *good* isolation
transformers in the signal circuits. These allow equipment interconnections
to be made without concern over mixing "ground" connections.

Again, sorry if this seems to fly in the face of everything you have ever
read, been told (especially by the ARRL and FCC!), or experienced for 35
years or whatever. But, as William found out - and Bob Heil knows in
infinite detail - "grounding" in any electronic system is not accomplished
by just automatically connecting "everything to everything" and then to
something called a "ground." Some of the most intricate and detailed
engineering of large electronic systems is involved in choosing and
installing "grounds."

My regards and thanks to Bob Heil for all that he has taught me about this
important aspect of system engineering.

73, George W5YR
Fairview, TX
w5yr at att.net
http://www.w5yr.com


----- Original Message ----- 
From: "William Diamond" <wjdiamond at sbcglobal.net>
To: <icom at mailman.qth.net>
Sent: Thursday, July 29, 2004 10:04 PM
Subject: [ICOM] Icom, Grounds and Mikes


> HI folks,
>
> Well, I never liked eating fowl, much less Crow but I guess my time has
> come.
>
> As some of you may recall, on the olds radio room, I had tried several
Heil
> Gold Line mikes on the Icom rigs with terrible results. Howls, transmitter
> output with no mike gain turned up, distorted audio and splattered
signals.
>
> Finally I removed all the Heils and started using Icom SM 20 mikes with no
> problems....
>
> I really like the looks of the Heil Classic mike with the Call letter
plate
> so I bought a new one a couple of weeks back.  This was the Icom only
> version.  I really did not intend to use but I thought what the heck, so I
> hooked it up to the IC 781, a total disaster.  Then I tried the 775DSP,
same
> thing in fact on every single Icom rig it was unusable.
>
> I emailed Bob Heil about it and talked with him by phone about the problem
> so he asked me to send the mike to him for testing so I did.
>
> It worked perfect in fact Bob even recorded an on the air test using it
and
> sent it to me.
>
> So, what was going on?  Bob thought it was RF feedback caused by ground
> loops.
>
> I started trying several SM 20 mikes listening with headphones and it was
> there also but not as bad because I did not have to run the mike gain as
> height.
>
> I talked with some experts in the field of grounding and ground loops and
> found out some interesting information.
>
> I removed every single ground from all of the stations and tried the Heil
> mike and it was great, I even tried an old Gold Line that I had in the
> closet and it too worked fine.
>
> So it would appear that the problems were not with the mikes but my
station
> setups. Please note, this is all brand new rigs, nothing orig. left.
>
> So, I zinged Bob's mikes and I was wrong (eating Crow) and I apologize.
>
>    WILLIAM J. DIAMOND
>   ROGERS, ARKANSAS USA
>
>  HAM RADIO OPERATOR WR0T
>  VISIT MY RADIO SITE AT
>     wjdiamond.com
>
>
> ----
> Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
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