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Author Topic: A good earth ground  (Read 1549 times)

Posts: 21

« on: September 12, 2001, 11:01:27 AM »

I understand the need for an earth ground.  I rent a single family home and have done a thorough inspection.  The cold water pipes are inadequate for a good ground and I cant find an exisitng ground.  I am uncoforatable with using the ground plug of an electrical socket, as I have read about this option.

What options do I have?  How difficult is it,a nd expensive, to install the 8 foot rod i have read about.  This seems like it could be a projct.  Keep in mind I do not own the house and will not be there for much longer.  

Thanks in advance

Posts: 20547

« Reply #1 on: September 12, 2001, 11:32:30 AM »

Unfortunately, much of what has been written about the "need for a good earth ground" is hogwash, based in nothing of substance and written by people with a very limited understanding of ground systems.

There are three types of grounds of concern to hams, and two of them are of very little practical use in most cases:

1.  Utility ground return: This may or may not be at real "earth ground" potential, and it does not matter if it is or isn't.  What does matter is that wherever the "common" of your AC power utility rests, you want to have the chassis of your electronic equipment, including ham gear, resting at that same point.  That point _is_ the "ground prong" potential of your 3-wire AC outlets, which is common to the chassis of your service panel, and is common to the "common" of your utility service.  It could be floating well above real earth ground, and that matters not a wit.

2.  Lightning protection ground: This has nothing to do with item (1), or item (3) that follows.  It's merely an effort to provide a lower impedance path for lightning to find its way to ground, without going through your home or equipment.  If you live in a region with lightning activity (I do not), consider grounding all outdoor antennas and supports via the heaviest possible conductor(s) to earth, _outside the home_ (!!!!), using a shorter path than your transmission lines that bring the RF signals into and out of your shack.  And don't let those conductors come in contact with anything flammable or combustible, like your house.  That's it, in a nutshell.

3.  RF ground: Absolutely not a requirement in most cases, especially if you're using resonant, tuned, current-fed antennas (those fed with coaxial cable feedlines and tuned to have a good impedance match to that cable).  However, if you're using voltage-fed antennas (long wires, for example), and especially if you're bringing a long wire into the shack, an RF ground can help a great deal, both in terms of actual antenna performance and also alleviating ill effects of excessive RF floating around the shack, equipment and home.  Bringing radio equipment chassis down to "real earth ground" potential, which should be zero or nearly zero, helps to prevent RF feedback, burns & bites from "hot chassis" and "hot mikes" and other accessories, and so forth.  It's much nicer when you can operate calmly without worrying about if your microphone is going to give you a shock or burn from RF every time you touch it!  An RF ground helps a great deal for this.

However, having said that, I run a kilowatt of output power on many bands (160 meters through 2 meters, inclusive), and have for many years, very effectively with no RF ground at all, nor any attempt at an RF ground.  It's easily done, if you use 50 Ohm antennas fed with 50 Ohm coax.  All the RF is up at the antenna level, there isn't any significant field radiated or conducted into the shack, and there are no ill effects.  I cannot recall ever using an RF ground, in 36 years of actively operating from dozens of homes and temporarily station locations.  But, if you want one, go for it.  An RF ground would normally be attached either to your transmitter, or to your external antenna tuner (if you're using one), via the broadest, shortest conductors possible attached to earth.  A single 8' ground rod is unobtrusive and in most cases can be slammed into the ground quite easily, and just left behind when you move.  Nobody cares about a 1/2" piece of rod sticking a few inches out of the ground, close to the foundation of the house.

Whether an 8' ground rod provides you with an RF ground or not is a variable.  It might help, it might not.  Probably cannot hurt.  A "serious" RF ground is usually provided by a _field_ of wires and rods in the ground, spread over a large area.

73 de Steve WB2WIK/6


Posts: 537


« Reply #2 on: September 16, 2001, 07:19:25 PM »

< Unfortunately, much of what has been written about the "need for a good earth ground" is hogwash, based in nothing of substance and written by people with a very limited understanding of ground systems. >

Why does this myth persist?  Anyone?  I think it harms amateur radio, because new hams are intimidated by this.  Think of all the times you hear people say "I can't operate on HF, because I live on the Xth floor and cannot get a good RF ground".

I have also noticed that nobody can explain where the stray RF comes from and how the earth ground addresses it.  It sounds as if everyone simply copies what everyone else says.

Posts: 20547

« Reply #3 on: September 17, 2001, 02:18:39 PM »

Back in the early days of wireless, antennas were normally fed with a single wire, or a set of wires, and it was common that the transmission line and radiator were one in the same; thus, RF in the shack was not "stray" at all -- it was part of the system, and both known about and intended.

Securely "earthing" (grounding) equipment chassis brought the chassis back down to zero or nearly zero RF potential, and prevented RF burns and shocks to the operators, not to mention lesser maladies.  It worked.  For similar installations, it still works.

But coaxial cable changed a lot of things.  Coax has only been commonly available since the late 1940's, and hams began using it around 1950 or so.  This wonderful, shielded transmission line allowed one to literally "ground" the shield anywhere he wished to, and when used to feed antennas matched to the same impedance as the line, coax "quieted" down many a ham radio station to the point where the need for grounding is essentially eliminated.  If there's no RF voltage floating around on equipment chassis, why use a ground?  There's really no need, and no reason.

Most of the RF in hamshacks nowadays is not "stray" by any means, it's radiated by the antennas and simply present in the shack due to near proximity to those antennas.  Not much we can do about this, other than add more separation (best solution), or start building shielded operating rooms (expensive, claustrophobic).

73 de Steve WB2WIK/6

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