Dale, as an EMC/RFI engineer (and a bit more with RF/uW design and
testing), I have been in and used many Lindren chamber installations.
"Grounding" is always an issue which is most times overlooked by the
average construction worker.
When Sun bought StorageTek here in Northern Colorado and forced us to move
to their campus literally across the road, they assured us everything was
"grounded" per code. Well........a couple of months after moving in, two
of us engineers traced things out based on measuring 67 Vrms from our
EMC/RFI setups to the building steel structure. We got "buzzed" by running
the back of our hand over the steel structure while the other hand was in
contact with our setups. Sure enough, there was no "ground" rod or any
wire that could have ever connected to a "ground" rod. We called in the
county inspector who made it happen.
Personally, I do not like the term used in the US: "GROUND". Amateur radio
operators make something out of "ground" that truly does not or never did
exist. "Ground" this....."ground" that......assure everything is
"grounded"..... bla...bla...blah....blah... . . . . .... They approach
"ground" as though it's the Holy Grail of all things evil associated with
RF fields and waves. They "might" (????) understand if they only LEARNED
SOMETHING in taking the exams to become licensed. But they don't.
For all these reasons and more, I MUCH PREFER the Brit's term: "EARTHING"
Just a connection to the earth as a sink - nothing more....nothing less....
Dave - WØLEV
On Sun, Jan 26, 2025 at 5:02 AM Dale <svetanoff@earthlink.net> wrote:
> Dave (and anyone else interested),
>
> I have heard others voice comments such as you make with respect to
> lengths of grounding conductors and their subsequent self inductance. As I
> stated in my prior post, my guidance for my station's grounding scheme was
> MIL-HDBK-419A, a juicy little tome in 2 volumes and available as a free PDF
> download. It is (or was) used as the standard site grounding scheme for
> most military fixed installations. The key features are complete ground
> rings around each building, tower, or fixed asset, and bonding of all RF
> system grounds to the main site power distribution ground.
>
> The installation I described in my prior post is based around a house that
> is about 54 feet wide and about 35 feet deep. When only the basement walls
> and concrete footings were in place, I installed 14 ground rods (each 8 ft
> long by 5/8 in diameter copper plated steel) around the outside of the
> footings and foundation, with most of them Cad-Welded to the more than 200
> feet of 00 gauge bare copper stranded wire that is buried about 1 foot
> beneath the backfill soil around the foundation. (I ran short of Cad-Welds
> and had to use compression clamps to bond a few of the rods to the wire.)
> That wire forms a complete loop around the foundation. The ham shack is at
> the north end of the house and the electrical panel is at the other end.
> Thus, it was very important that I installed a short jumper wire between
> the power panel grounding conductor and the loop. The NEC defines that as
> an auxiliary ground connection. Each of my 3 towers has a full ring ground
> around its base and those ring grounds connect to the main loop.
>
> Now, a final word about ground rods: Prior to coming to Rockwell Collins,
> I was chief electrical engineer for Lindgren RF Enclosures, Inc., a major
> manufacturer of RF shielded enclosures for military and numerous other
> applications. Those Faraday cages were equipped with power and control
> line filters as needed for uses of the chambers. The filters were designed
> with conductive cases that were directly mounted to the wall and/or ceiling
> of the enclosure. Since the filters pass all impinging energy to the case,
> it is important that the filter case (and the shielded enclosure) be well
> grounded. It is also essential that power filters (for 50 or 60 Hz
> applications) have a low impedance path to the power panel so as to
> minimize shock hazards.
>
> I got a phone call from an industrial customer who complained that he was
> getting shocked anytime he touched the enclosure and an external grounded
> object (such as a water pipe or metal building column). He told me that
> the enclosure had been stalled about 3 or 4 years ago on the factory
> floor. Two 8 foot ground rods were welded together and passed thru the
> concrete floor. He had faithfully poured salt water down that hole to
> maintain conductivity. I suggested that he check the rod and sure enough,
> only the top 3 feet of that 16 foot rod still existed.
>
> There is a solution for that problem. When drilling or setting a ground
> rod into an area of low electrical conductivity, use a material called
> Bentonite Clay. I got that info from a California company that specializes
> in difficult grounding situations.
>
> 73, Dale
> WA9ENA
>
>
>
>
>
>
> -----Original Message-----
> From: David Eckhardt <davearea51a@gmail.com></davearea51a@gmail.com>
> Sent: Jan 23, 2025 3:29 PM
> To: <jim@audiosystemsgroup.com></jim@audiosystemsgroup.com>
> Cc: <rfi@contesting.com>, Ham-Antennas <main@ham-antennas.groups.io></
> main@ham-antennas.groups.io></rfi@contesting.com>
> Subject: Re: [RFI] FW: RF noise and ground
>
> The average ham's concept of "ground" is usually completely off the wall
> and absolutely incorrect. As Jim stated, "ground" (the Brit's got it
> right using the term "earth!) is not a sump/sink for everything bad
> associated with RF and/or RFI.
>
> How many time do we hear or read as a "solution" to RF-in-the-Shack:
> "Connect a ground"? BS!! What if your "ground" *(earth) conductor is
> 33-feet to your "ground" (earth) connection? That's a quarter wave on
> 40-meters, so you have a floating - open circuit - to your "ground" (earth)
> connection. Also, its an open circuit at odd harmonics of 7.15 MHz. Do
> you have a reliable "ground" (earth) connection? Absolutely not!
>
> In addition, "ground" rods are NOT sufficient for lightning remediation.
> They are highly resistive to the preverbial "RF garbage sump/sink" that
> most hams believe a single "ground" (earth) rod provides. Further, for
> them (notice plural) to remain effective over time, they must be
> periodically treated with a solution of CuSO4 (blue vitrol) or NaCl (garden
> variety salt).
>
> The absolute most important item to address in lightning remediation is
> that everything of concern (electronics) floats up and down in potential
> together. That requirement eliminates a "standard practice" of connecting
> everything together with copper wire, even of heavy gauge copper wire. When
> 10-thousands of amperes are encountered from a lightning strike, even
> nanoHenries of inductance forms a reflective circuit element! Look at the
> feed coax at the very base of any AM BC transmitter. The coax cable is
> usually dressed in a large loop before it enter the tower. This loop
> introduces enough +jX (inductive reactance) to keep "most" of the
> potentially damaging elements of the strike out of the matching network and
> transmitter. The requirement I described requires EVERYTHING of concern
> sit on a large highly conductive sheet and each piece of equipment of
> concern be BONDED to that highly conductive sheet. Doing so results in no
> potential differences (high voltages) between the electronics placed and
> bonded to that sheet. A connection from that sheet to "ground" (earth)
> then bleeds off any charge the sheet may have accumulated.
>
> Thanks, Jim, for motivating me to write this email!🙂😀😉
>
> Dave - WØLEV
>
> On Thu, Jan 23, 2025 at 7:15 PM Jim Brown wrote:
>
> > On 1/23/2025 4:30 AM, nlsa@nlsa.com wrote:
> > > Question: I’ll bet that my noise floor could be improved by a
> better RF
> > connection to Earth, but how can I do it? What mode does EMI take in this
> > situation? What is “ground” in a non-metallic enclosure?
> > >
> > The earth is not a sump into which noise is poured. The ONLY reason for
> > an earth connection, and it is ABOUT LIFE OR DEATH, is LIGHTNING
> > PROTECTION, and it is required by LAW. So is the bonding of everything.
> >
> > I would not expect any noise reduction at VHF from an earth connection,
> > but proper grounding and bonding is required by Electrical Codes, which
> > are LAW, and for human safety.
> >
> > 73, Jim K9YC
> >
> >
> >
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
> >
>
>
> --
>
> *Dave - WØLEV*
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>
>
--
*Dave - WØLEV*
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