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Does the G5RV use a balun or not? | Surge Suppression? | Page Five Title | What's Ground Got To Do With It?
from the w5dbg Notebook
What's Ground Got To Do With It?

The earth is a sea of electrons:

It can give and take electrons as needed. It is, therefore, an 'equalizer.' Putting down a ground rod in that resevoir is a lot like deploying a sea anchor. When the going gets rough, it will keep you oriented.

To ground or not to ground.

You may hear this regularly: 'I have never grounded and I've never had any problem.' This would be like me saying that I live on the plains in a compact motorhome and have never been turned over by the wind. Same answer: Lucky! Because like it or not, your station is capacitively coupled with earth. Lightning induced currents on an ungrounded station can knock you out of your chair! It goes like this:

Commonality is the key. The earth is the most common thing around. Therefore, you do ground. If commonality is the key, what do we do with electrical ground?  The answer is: You do include electrical ground.  Bottom line: Any connection with earth is better than no connection.


Safety ground in a nutshell:

There are basically five reasons to ground and they are all about safety. The obvious reason is the direct hit of lightning. Let's face statistics. You're not likely to experience a direct hit but then people do win lotteries. The other four reasons are everyday occurences. Stray currents from equipment, especially old equipment with failing filter capacitors, can bite you. They need to 'go to ground.' Stray RF needs to be attenuated. And static buildups need to be equalized. These discharges of sky and earth can actually prevent lightning by keeping the charges down. ( See ESD on the home page.) And lightning-induced currents can be huge and injurious without a sink. (See Surge Suppression?)


We've Had It Wrong

We've taught each other over the years to bring a feedline to the radio and then to ground the radio with the shortest possible connection. Wrong. Here are at least three good reasons why: First, you are giving lightning a path to enter and putting the radio and yourself in that path. Second: When you unplug as you will surely do at the first sign of lightning, you'll have the sky in one hand and the ground in the other. This could be lethal. Teaching this practice is almost criminal. Third: The RF problems are compounded with the old approach. If you don't have a short connection to ground, you could find the radio in a standing wave of RF voltage. That rf burn you feel when your hands are wrapped around the D-104 is exactly that. In hindsight, putting the radio between the sky and the earth must have been somebody's idea of a joke.
 
I understand how the practice evolved.  It evolved while treating the symptoms of RF, Static Bites, etc. To clean up the shack, you have put the ground between you and the sky and most issues will disappear. 


Get It Right

The hardest thing about this is to change one's mind. When you put something up in the sky, you are creating an 'air terminal'. The correct thing to do with an air terminal is to ground it. If you will bring feedlines to ground before you drape them through a window, you create a kind of 'bulkhead' where lightning can be seriously dissipated before it can enter. This is a great place for a filter-type lightning arrestor. (See Surge Suppression?) That coax from ground could now be station ground. When you unplug this radio, you have the ground in hand (not that that's the safest thing in the world either.) And you're disonnecting from the sky and the earth in one action. That loose end ought to be plugged into ground as well. If you'd like my advice, set your station up perfectly well and leave it the hell alone.


The bulkhead:

A sailor told me about a lightning strike on his sailboat which followed the feedline into the cabin through the glass port. The strike blew out the glass and lacerated his face. He probably lived only because of a serious ground connection to the sailboat's keel. The radio was destroyed.

This helped me change my mind! Until that QSO, feedlines used to enter my compact motor home through the vent windows. After that, they got plugged into the chrome bumper before entering through the firewall.

Here's an idea whose time has come: Put a metal plate in the window. I think this could be galvanized flashing on plywood but a quarter-inch thick copper or even aluminum would be better. Mount coax connectors or feed-through insulators for twin lead. This would be a good place for a balun going to open-wire line. Or those lightning arrestors.


Why use knife swithes and grounding relays?  A good filter arrestor grounds the antenna full-time and disconnects the radio full-time for DC and low frequency ac.  
 
Plug all feedlines into the plate as though it were a chassis. And ground the plate outside to rod or rods using very beefy connections and conductors. Flattened and bolted copper pipe might be the ticket. Because if there is a strike, there will likely be a few more in sequence. You don't want this connection burning off like a fuse. If you absolutely love draping feedlines across the yard, buy a weatherhead at your local electrical supply. Ground it. Then try to figure out how to ground the coax shield.

Let's discuss it! w5dbg@yahoo.com


RF Feedback?

This approach will reduce many of the rf problems encountered when you're in a second story room. The ground will do a lot to attenuate rf. If there is a problem , coil the coax before the radio to block the rf without impeding the path for dc and low frequency ac. At W5DBG, I frequently coil the coaxes before they plug into the bulkhead. Don't worry! Those coils won't do much to impede the currents of lightning to ground.

Put the ground between the station and the sky! Think in terms of bulkheads.


Working against ground you say?

When I was a kid, I used to hear an ol' boy sign like this:

"In case y'all 'r wunderin' why this is such a gaul darn bodacious signal, it's due to the pair of fifty-five gallon oil drums full of Arkansas white lightning buried in the ground!"

A common misconception about ground is that antennas must be worked against it. I have even seen this in print in recent years so it's hard to blame hams for repeating it. One author suggested working a random wire 'against ground' by putting a random wire under the random wire and connecting it to the radio ground. ('Random' is a word we use when we can't or won't define terms. The study of antennas strives to define these unknowns.)

If that 'random' wire is at it's quarter wave, the wire under it will complicate the scheme considerably. It could even cancel all broadside radiation. Now I'll grant that at the quarter wave , this antenna needs the counterpoise. It would be better to run it off at a diagonal or perpendicular or the other way or why not go ahead and make it a dipole and be done with it. At it's half wave, the 'random' wire is a dipole with a standing wave of current in the middle. You could call it a 'zepp.' Contrary to popular belief, it is perfectly resonant and capable of making a maximum current without 'working against ground.' Grounding the wire under it could actually cancel the radiation, deform the pattern and/or bring a lot of rf into the shack. The author could have suggested that any wire under a wire can reflect and improve performance. You lovers of inverted vees need a half wave under the dipole to improve radiation pattern.

It would be better to have this 'ground plane' elevated but it could be embedded under the grass roots. It should NOT be connected to station ground. You wouldn't ground the reflector of a yagi! Not if you were a purist. And certainly not at its tip. Of course if you're going to accept the 'scatter beam' concept you might as well discover loops. (See the home page)

The concept of working against ground likely was born with Marconi who got a huge performance improvement when he added the ground to his transmitting scheme. He, in effect, enlarged the antenna and dropped the operating frequency which may have caused the RF to 'hug' the ocean all the way to Newfoundland. At the time, Edison was saying that the 'radio' would be lost in space. Heaviside was advancing the theory of an ionosphere. My personal theory is that the RF kept 'shearing' its way along the ocean's surface. Radio travels through seawater at one/ninth the speed of light.

The classic Marconi is a quarter wave resonator which is only half an antenna without it's anti-phase or counterpoise. This is the only case of 'working against ground' that is valid. At low frequencies, using ground may be unavoidable. A 160 meter quarter wave vertical at it's full size would be 135 feet tall. It would still be only half an antenna without ground. Now everyone knows that radials improve this equation. But these aren't necessarily grounded. The entire antenna can be elevated and fed balanced. Did you know WWV uses the elevated vertical with sloping radials for 20 MHz at a height of about 25 feet? Their power level at that frequency is only 15 or so decibels better than a hundred watt ham station. Very effective! (See NIST link)

To be perfectly clear about this: Antennas do benefit from intelligent reflective surfaces and spacing is everything. But making those surfaces part of the ground system is unecessary except in the case of the quarter wave and other undersized elements. Using ground will help you 'load'.  It will change impedances but this is not to say that the antenna needs it.  Your sense of matching needs it!  Don't let us hear you say you're working your 'longwire' against ground. It leaves the impression that end-fed wires are somehow incomplete.  If you've paved the property with chicken wire I'd say you have a good reflector which does seem to improve performance. It does not need to be connected to the station's ground system. That could be very problematic. Even noisy.

copyright 1996, 1997, 1999, 2001 C.D. Economos

The screwdriver ground.

I used to use a screwdriver to ground the motorhome when operating portable. It had a wire connected to the frame. One of my favorite authors, J.J. Carr, K4IPV, made fun of this in one of his books. But I have news for y'all. Any connection is better than no connection. However...

The better the connection, the safer the station. While a screwdriver at a field day station will dissipate static and reduce lightning-induced currents an eight foot rod will do it better. And in the case of a strike, will surely sink more current. Several ground rods, four to six feet apart are best. Why rods? Because they keep the tips in moist soil and below the frost line. Frozen soil is an insulator.

The anecdotal evidence: I used to feel the chassis of my Drake TR-4c to sense lightning-induced currents. (Don't do that! Just take my word for it. Unless you'd like to do it seriously. You could use a data recorder and share the results.) As I continually improved grounding, I felt less and less 'bite'from the chassis during storms.

Why a six foot spacing on rods? First of all, air terminals and ground rods have a cone of influence that generally has a diameter equal to the height. In other words, a mast can protect an area of that size when performing like a lightning rod. Ground rods have a similar priniciple. To get the maximum effect of lowering resistance, spacing matters. And don't expect three rods to reduce ground resistance to one-third. It's more like one-half. In the unfortunate event of a direct hit, I think you'll find it's worth it.