Aterramento Da Estação

http://www.eham.net/articles/8951Parte superior do formulrio

Parte inferior do formulrio

Aterramento da Estao

Ser que algum dia ser capaz de dissipar os mitos?

Steve Katz, WB2WIK / 6

STATION GROUNDING

Will we ever be able to dispel the myths?

Steve Katz, WB2WIK/6

This is a much beaten-up subject. Hardly a day goes by that on some ham radio board or reflector there isn't a question about station grounding. Funny part is, the subject's been so discussed, that anyone asking a question must have not been paying attention for the past several (fill in: days, weeks, months, years).

Problem

I think the biggest problem is that a lot of commercially manufactured equipment comes complete with a ground terminal, usually somewhere on the rear of its chassis. That, along with directions from the equipment manufacturers, implies the equipment owner ought to connect something to it.

I view this as an adjunct to the SWR dilemma. You know, the one that drives hams crazy believing that for an antenna to work properly it must have a low SWR. Or, sillier still, that an antenna with a low SWR must be working properly.

It's funny that before about 1960, few hams owned an SWR measuring instrument of any sort but somehow made DXCC, bounced signals off the moon, worked meteor scatter, aurora and E-skip, and just happily made contacts without having the foggiest idea what their antenna's SWR was. Commercial transmitters didn't have internal SWR bridges, and inexpensive bridges weren't on the market. The famous Monimatch circuit hadn't yet been published, so few hams knew how to build an SWR bridge, nor would they bother trying. Hams, and their transmitters, were perfectly content to be working each other, around the world, without this fabulous knowledge.

Now, back then it was also pretty common for a lot of equipment to not even have a ground terminal. Some of it did, some of it didn't, and it didn't matter much one way or the other. I think the best reason for a ground terminal would have been to help prevent equipment users from killing themselves due to internal short-circuits in equipment that was AC powered, back before 3-prong (and 3-wire) power cords, plugs and outlets became common.

Ironically, the most unsafe equipment back in those days was thousands - if not millions - of inexpensive, AC-line powered broadcast radios, including bedside All American Five type radios and clock radios, which did not use AC line isolation transformers. To minimize production cost, a lot of these radios directly rectified the AC line and fed a full 120 volts AC to a series string of tube filaments. The string totaled around 120 volts, so no filament transformer was needed. One side of the AC mains was connected directly to the radio chassis (preferably, the cold side of the mains!), and to prevent people from touching the chassis, the little radios were installed in plastic enclosures and used plastic knobs over the control shafts. These radios did not have 3-wire power cords.

Those were accidents waiting to happen, of course. Untold thousands of people received electrical shocks from these radios, and they were responsible for more than a few fires. Sadly, some probably lost their lives due to such shabby design.

And while those radios really indicated an actual need for a chassis (earth, safety) ground, they didn't have any provision for one.

But we don't use radios like that any more. Now, we have equipment that uses isolation transformers, and 3-wire power cords plugged into grounded outlets. And a lot of our equipment is powered by low voltage DC, where a shock hazard is literally nonexistent. (You can be hurt by low voltage DC, but not electrocuted. The major source of injuries to people working with low voltage DC is in the form of burns caused by jewelry shorting out the DC power supply's output bus, which can often pump dozens of Amperes through a ring or bracelet before shutting down - if it ever shuts down.)

So, why do we ground?

Really good question. I guess I'd preface my answer with this simple statement:

I've been a licensed ham for 39 years, and continually active. I run legal-limit amplifiers and power output on 160 meters through 10 meters, a kilowatt on 6 and 2 meters, and a couple hundred watts on 135cm and 70cm, and sometimes on 33cm and 23cm, too. I've used dozens of different antenna configurations and have operated from all over the world, but mostly from any of the fifteen home-station hamshacks I've built over the years at the various homes I've owned.

And in all that time, I've never once had a station ground of any sort.

And in all that time, I've never had any problem that grounding would solve.

I've operated mobile, marine mobile, maritime mobile and aeronautical mobile and never had a ground on any of these vehicles, either. Especially when operating from an aircraft, that's hard to do. I've also set up dozens of field operations, including Field Day and other contests, without ever owning a ground rod or feeling the need to drive one in, anywhere.

Therefore, you can see I'd be a tough one to convince that a station ground serves any particular purpose. Not to say it cannot help, in some situations. But in most all those situations, better station engineering would help more.

(For clarification: Nowhere in this article will I say it's a bad thing to ground your equipment. I just discuss the counterpoint, that grounding your equipment usually isn't necessary, and if you're spending any time deliberating on this issue, that's time wasted that you could be operating, instead.)

RF grounding

There's surely such a thing, and it's a good thing. If I ever use a voltage-fed antenna or a random wire, I usually place my antenna tuner outdoors, or at least in an open window, so the entire antenna is literally outside, and then I have a very short and direct path to Mother Earth for the return current. The earth completes the current path from transmitter to antenna and back, and everything is happy. This is a great situation. But you really need to have the tuner laying on the ground, or very darned close to it, to accomplish this feat - because a tuner sitting on a desk in the shack is often too far from ground to be effectively grounded.

Usually, however, I use current-fed antennas and I match the antennas to their transmission lines (by adjusting the antennas themselves). Most of my lines are coaxial cable, but some are twin lead. If I use coax to feed a balanced antenna, I use a current balun at the antenna feedpoint. If I use twin lead to feed a balanced antenna, I don't need a balun, except perhaps in the shack where I transition to 50 Ohm equipment. In all cases, the lines are cool and quiet and don't seem to bring any RF back down the pipe from antenna into the shack.

That's the result of matching, choking and cable routing to minimize this problem. That not only works better than grounding the station equipment, but it's also easier to accomplish, usually.

It's true that most antenna designs won't provide a good match over more than maybe 2% of the operating frequency. So what? My 80 meter inverted vee is resonant at 3.750 MHz, and its SWR rises to >3:1 at both band edges (upper and lower). Yep, that's about 25% reflected power. Okay, I'll repeat: So what? I use my amplifiers as antenna tuners, can transfer all the power generated to the load just fine, and have zero RFI, RF feedback, or other problems. No hot mikes, no burns from accessories, no nothing, nada, zip. The secret is station engineering. That is, my antennas are located sufficiently far from my equipment that very little radiates back into places I don't want it to be. And, I do use current baluns in the form of coaxial RF chokes and the like; and, for stubborn cases (especially on the very lower frequency bands, where it's difficult to escape the antenna's near field) I use ferrite isolators on the feedlines, installed just outside the shack wall.

I obviously don't need any station RF ground, and never made any attempt to have one.

Lightning

I live in Los Angeles, which has the lowest incidence of lightning strikes of anywhere in the U.S. (fewer than 5 lightning incidents annually on average, and that's recorded in the mountains or high desert, not where I live). But, it doesn't matter. I grew up in New Jersey (70+/year) and have lived in Florida (90+ but it seems like a million), and have operated from many tropical places where lightning is so common that people miss it if it doesn't happen daily.

Fact is, grounding your equipment chassis inside your home doesn't do anything to prevent lightning damage, anyway. The last place you want lightning energy to find a path to earth is inside your home. The only place you want lightning energy to find a path to earth is outside your home. Volumes have been written on this subject by people more knowledgeable than I, so I'd refer you to those volumes for more information.

The only thing I'll say is, Equipment (chassis) grounding is not helpful with regard to lightning protection. And that fact ought to be self-evident to anyone who understands electricity.

Safety ground?

As I mentioned earlier, there are very valid reasons for safety grounding, although I've never once had an equipment fault that would have caused a safety concern whether the equipment was grounded, or not. But, it's possible. And, it's the reason that all construction in the past 30+ years in America (and many other places) used 3-wire grounded outlets throughout. The third (green, ground) wire should be connected to the ground buss in the building's electrical service panel, which should be grounded directly to earth via an 8' ground rod driven into earth at the nearest practical location, usually directly under the panel.

It's possible that even this excellent protocol can fail, but it's rare. In the event it does fail, a secondary earth ground for station equipment is a belt and suspenders approach that probably can't hurt. I must say, though, that having owned hundreds of pieces of AC-powered electronic equipment in my nearly 40 year ham career, I've never seen a fault occur that would cause an electrical shock during normal operation. So, I do believe this is a pretty rare event.

[I might also say that I've received numerous electrical shocks over the years, all of which were purely my fault (like replacing wall outlets and switches without bothering to turn them off first), so I deserved every one of them. And they didn't feel so bad. I can say from experience: 240v hurts much more than 120v. If you're going to shock yourself, go for 120. It's much nicer. In Japan, their mains voltage is only about 100 volts. Now I know why: It hurts even less.]

Daisy chain grounding

This is not recommended at all, but we all have it, in one way or another. Unless your station is set up an inch from your service panel, where a SPG (single point ground) connects every single thing going to and from your home and the impedance between all those items is zero: You, too, have some form of a daisy-chain ground.

This is nothing more than having equipment grounded via multiple paths, both serial and parallel, that have varying impedances to earth. It's difficult to avoid.

For example: If your antennas are mounted on your tower, and your tower's grounded, your antennas, unless completely isolated from their supporting structure, are grounded, too. Now, you use coaxial cable to connect those antennas to your station tuner, coax switches, amplifiers, rigs, or whatever, and you have a ground path from your antennas far, far away to your station equipment right in front of you, via all the coaxial shields. The DC resistance of all those shields is an unknown, although you could probably calculate or even measure it, if you try. But, if you have four antennas fed with four runs of 100 feet each RG-213/U, you've got four parallel ground paths that probably have a DC resistance less than one Ohm.

So, even if you disconnect every intentional earth ground you have in your station, your station equipment is still grounded, anyway. It's just a rather unpredictable ground. If you don't have a tower, but use a mast on the chimney to support your antenna, that mast should be grounded by a wire of substantial diameter directly to a ground rod via the shortest possible path. If you use a doublet antenna that is fully isolated from ground, then its feedline should be grounded via a lightning arrestor or similar device prior to entering your shack.

No matter how you cut it, your stuff is grounded (if you have an engineered installation), like it or not. So, the safety ground consideration, to prevent electrical shock in the event of internal equipment malfunction, is very likely covered. A 1 Ohm connection to earth will keep a 120v line down to 15v before it trips the 15A circuit breaker or fuse in a conventional household circuit. You won't feel the 15 volts.

If your home is equipped with 3-wire grounded outlets and your power supplies or other equipment containing AC-powered circuits have 3-wire power cords, now you have another ground, in parallel with that one.

If you added still another chassis ground simply because you wanted to, now you have still another ground, in parallel with the other two. But the circuit is more complex than just parallel branches to earth, and from an AC (RF) perspective it's more complex still.

As far as I'm concerned, the only important consideration in all of this is that the transmission line from my antennas to my station equipment should have considerably higher ground impedance than the outdoor ground connection from those same antennas to earth. So, when in doubt about that, I use more coax than needed for the path. This is purely a lightning protection issue, and I live where lightning hasn't been witnessed in sixteen years; but I try to follow that rule, anyway.

Still want to connect something to that little terminal?

Go ahead, if you want to. But think about why. Because the terminal is there isn't a very good reason. The little pictograms in the ham radio equipment owners' manuals (especially the JA stuff) isn't a very good reason, either. My Kenwood owner's manual has the little grounding pictorial, along with a warning to be sure the equipment is grounded, with no explanation at all as to why. Interestingly, I have lots of Kenwood audio equipment that doesn't even have a 3-wire power cord, and there's no ground terminal on any of it. Same company, different philosophy.

Maybe Kenwood believes that because amateur transceivers are capable of transmitting, they -- unlike receivers -- need a ground?

Even more interesting is the fact that the stereo equipment really could benefit from an earth ground. In one case of RFI I had personally, adding a ferrite choke filter to the AC power cord, and a chassis ground to a surround sound stereo receiver, completely eliminated the interference.

Let the flames begin

The must ground crowd - and there is one, somewhere - will likely disagree with all of this. That's fine. Remember, this whole piece is not about lightning protection in any way; it's about interior station equipment grounding. Since I've never used any in 39 years, I probably never will. I'm not suggesting that equipment grounding is wrong, just that it's usually unnecessary - and if you find it to be necessary, you've got other problems that can be fixed in other ways.

WB2WIK/6

Member Comments:

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Station Grounding

by KY1V on August 17, 2004

Mail this to a friend!

Very interesting article Steve.

I would like to know more about the SWR information as I grew up with ham radio in the 70's and the SWR meter was an all important device needed for "adjusting your antennas".

Please do write another article about SWR. I would be interested in more details how to tune antennas with out the SWR bridge.

By the way, I am one of those guys with an 8' ground rod 2 foot from my shack and each device is grounded directly to a copper ground buss connected to the ground rod. No more than 4' from equipment to ground.

I think I may have to read your article a few times and dig up some old grounding information to better understand why I don't need it. Been a long time since I brushed up on grounding theory!

73,

David ~ KY1V

RE: Station Grounding

by ZL2AL on August 17, 2004


Likewise! I've been a ham for 50 years and never used an external ground in spite of all the dire warnings from the various men of letters in the usual radio handbooks. I have operated stations in this 230VAC part of the world and where I grew up in VE3 on 115VAC. Virtually any equipment I ever operated or built had a transformer of some sort which took care of isolating anything inside the circuitry from the main supply. I have experienced "hot lips" Most of us old timers have. Quite exciting really! The usual cause was a badly mismatched antenna and the usual cure was some sort of circuitry which matched the antenna. Funny thing! Hot lips disappeared when the antenna was matched. Modern day gear requires coaxial connections from radio to amplifier to various other devices around the station. RG8/u coaxial braid puts the chassis levels of all the devices at the same level of ground. Our 230VAC power system here in NZ has a three pin plug - one of which is ground and the second pin is called "neutral" which is connected to ground and the third pin is "phase" which is actually 230VAC above the other two pins. Ground is no problem. Running a separate line from each chassis to a ground rod driven into the earth seems fairly redundant to me.

Station Grounding

by W1CAR on August 17, 2004


I'm an electrical contractor by trade, so grounding anything is of profound interest to me. When I first became a ham, my theory was "let the station float," that is, until I saw what floating a station can do when induced lightning surged through one.

Lightning will strike, no matter what, when and where it wants to, despite any and all efforts we attempt to thwart it, or lessen the chances of being struck. Nothing will protect you from a direct strike. Nothing. Near strikes are not preventable either, but making an attempt to give the static another better route away from your precious station equipment is what I try to do.

When you leave the house, remove your rigs from the potential of being struck. A rig sitting on the desk completely disconnected from the power grid and coax will not be at any risk of being struck. Simply disconnecting the coax won't do, as we've discussed already, the rig is still connected to the power grid and all it would take is for the static charge to find a small path through your rig to gound...and I've seen that happen. Lightning near-strikes almost always damage or destroy all electronic devices in a home that give it a minor branch path to ground. This only happens because the static has no better place to go, so it finds many paths to dissipate itself quickly.

RF gounding is something I have not found to be useful unless I'm connected to a battery-only power grid that floats, and I key up and get a burn from my rig. When I go HF portable I bring a small 12" ground rod with some #14 standed cable and that takes care of that. Plus, I've noticed I get better signal reports.

RF grounding in my home station isn't something I have done either.. because my lightning ground outside one way or another provides that, via the ground braid in each run of coax. I have never had any problems in my shack due to lack of "hooking up something to that screw on the back of my rigs." The only arguement I can foresee here would be to provide your rigs with a "better" path to ground for proper RF grounding.. but that still lacks merit in my honest opinion.

So, bravo. Good thread. RF grounding seems a little overrated to me.. maybe we should have a good article written on lightning grounding sometime to add to this discussion.


by KA4KOE on August 17, 2004


One should never forgo a safety ground. More people are kilt outright by good ole 120 VAC, 60 Hz, than anything else.


by WIRELESS on August 17, 2004


One purpose of a chassis ground is to keep the potential difference the same on all equipment metal thats within your common reach. The chassis of a 'grounded' through the ground on a 3 wire plug can raise above ground level. There are many reasons why a metal grounded object like radios, electric stoves, air conditioners, refrigerators, etc. can go above ground level. I got one of the biggest shocks I ever got from touching a grounded electric stove and a water pipe because there was current flowing though the ground wire back to the box caused by another appliance.

Also keep in mind that most power strips are really cheaply made and I have seen grounds float inside of them.

Shorted or leaking transformers, bad insulation within equipment, fault current of an improperly wired device on the line branch, improper connections in the service box, regular and common leakage from some devices, etc. can cause a hot chassis even though they are grounded through the 3rd wire.

Even RF potential differences can result between equipment since regular ground wires can act as quarter wave transformers instead of grounds.

Making a general statement that chassis grounding is 100% unnecessary is stupid and indicates an uninformed opinion. The author should run his nonesense on engineers that design grounds for hospital equipment. They will laugh at him.

Station Grounding

by AL2I on August 17, 2004


Good article, and something I have seen in the commercial world as well. Many communication centers work fine for years, and then an expert engineer comes in for an appraisal and as soon as you can say "massive boondoggle", a grounding project is underway. Usually it is the bugaboo of "grounding loops" that sets off the flurry of sub-floor reverse copper mining.

Now there is a specific installation error that is pretty common in communication centers where the DC return is actually connected through the station ground rather than through the DC return, and this could (rarely) cause mischief, but I don't think Ham shacks would normally ever have this problem.

Steve (Super Elmer) Katz has done it again with another excellent sharing of his expertise.

Dave/al2i

Station Grounding

by KW4N on August 17, 2004


Steve: Good pushback article on common myths. There can't be enough of these since it's almost impossible to change strongly held beliefs. Many of these myths are perpetuated by slick marketing schemes to sell equipment. One common scheme is the cleverly written commercial disguised as an educational article. Lightning protection infomercials come to mind. They would have you think that unless you buy $100. of their equipment before you throw your transceiver switch again, you would be committing suicide.

Mark Twain said it all: "A lie can be half way around the world before the truth gets it's boots on."

With your relevant reference to the "SWR" myth, here's the truth on this matter written by people who knew something about electricity.

http://www.qsl.net/k4mg/Antenna%20Design%20the%20Easy%20Way.htm

73's Dave

Station Grounding



Wireless: What you say about grounds is true, especially your note about how RF sees those grounds, but I wonder if you have even read the entire article. You've re-characterized what was said, and most significantly, Steve did not say grounds were bad. I've always grounded equipment that had high voltage finals, and I suppose Steve would too.

(As I type this, my hands are inches away from my 25,000 volt CRT with nothing but the ground in a standard three-prong plug to protect me, and it is located a mere 12 inches from my 500 watt computer.)

73 Dave/al2i


by K3ESE on August 17, 2004


I always had a bad feeling that I was being lazy and unsafe with my ungrounded station. Those days are over, thanks to you, Steve! My head is held proudly up now.




Well, if you've never grounded in 39 years, then I guess you've not grounded the older stuff with high voltage finals. I assumed you would, but on a re-read, it seems that you wouldn't.

For the record, I feel any glow in the dark gear should be grounded for both simple safety principles, and for RF containment principles. RF signals at high voltages are harder to contain than RF signals that are derived from current-based, solid-state equipment.

73, Dave/al2i


by KT3K on August 17, 2004


I agree.

I haven't checked the schematic for my Astron power supply, but I'll bet it has an isolation transformer in it anyway. If you count on your third wire ground in your home A/C, you should have a ground rod outside at your electric box for your home. Some older homes use cold-water-pipe grounds. And those can be problematic. I would say it would be wise to specifically ground your station if your home uses cold-water pipe grounds. As for lightning, I grew up in Tampa, the lightning capital of the world. For a nominal fee the electric company, (TECO in Tampas case), will sell you or install a lightning arrester for your home. It's nothing more than a special fuse that goes in at your meter. It will blow protecting your appliances in the event of a lightning strike. If it blows, you get to buy another one. It's saved tons of equipment, but of course, nothing is 100% sure with lightning. You could have your equipment unplugged and lightning still get it. As for hospitals as mentioned in the thread... most hospitals have two types of grounds. A regular ground which is used for standard electrical equipment and appliances, like elevators, A/C and refrigerators, and an isolated ground which is used for computers and medical equipment. Ground potential differences can be a concern with some of the sensitive equipment they use, and differences in ground potential throughout a hospital at different stations could cause a lot of problems with equipment, medical and computer-based. Within buildings many elevator systems use high induction motors, and these motors put out quite a bit of load on the circuits they're on. So electrical system designs within buildings usually separate the high-induction motor systems onto separate circuits, on the regular non-isolated ground, and away from computer circuits.

Anyway, my station seems to run fine without running a special ground. Of course I do run a copper braid ground from my tuner ground to my radio's ground terminal.

Interesting thread, 73 John

Station Grounding

by KB9WQJ on August 17, 2004


Steve,

You said: " I use my amplifiers as antenna tuners ". Never having been QRO, can you explain this a bit? Do amps not need to "see" 50 ohms? There are "legal-limit tuners" out there...unneccesary?

Thanks. I appreciate the info and will eagerly read your answers.

Station Grounding

by OBSERVER11 on August 17, 2004


I will add this, I DO GROUND. I am not as rabid as some, my ground is only to prevent noise. I have several computers in close proximity to my ham gear and receivers. I ground the computer chassis'

YES! I KNOW, the computer case IS at the AC Main "ground potential", that is, the computer case is connected directly to the ground pin on the AC cord, so I am being redundant.

As a result of having the computer case as well as the radio chassis at the exact same potential, I do not suffer "ground loops" and my CRFI is minimal.


by K5DVW on August 17, 2004


Count me as a "non station ground" vote. I've been operating ham stuff for about 20 years and never had a station ground. Lots of RF grounds and certainly a lightning ground, but never have I connected that funny little screw on the back of the radio to anything. I figure the braid of the coax back to the lightning ground would serve a better purpose than the AC plug ground anyway.

I think the most important point is to have good engineering practice when setting up a station.


by W3JJH on August 17, 2004


OK, based on my experience around 250 W to 50 kW MF and 10 kW to 500 kW HF broadcast transmitters, I'm one of the "must ground" crowd. Here are my reasons:

1. AC Mains Safety--sometimes the insulation fails in equipment. If all exposed metal is either grounded or double insulated from live conductors, then a single insulation failure will not cause a dangerous condition. Normally, we can get a mains safety ground from the green wire in the power cable, but some equipment may require a separate ground wire.

2. RF Safety--when antennas are matched and balanced, there should be no RF in the shack. But antennas, balun, and feedlines can fail. Proper grounding provides a return path for the RF before it gets to the operator.

3. Home Owner's Insurance--almost all policies written in the US require that the wiring in the insured structure met local codes. Almost all jurisdictions incorporate the National Fire Protection Code into their building codes. Section 250 covers grounding and includes a subsection for Amateur Radio stations. If your grounding is not compliant with NFPC 250, then your insurance carrier probably will not have to pay any claims.

So, is everything grounded in my shack. Of course not. None of the low-powered, battery-operated gear is. There's no shock hazard, and any of the antennas that gear might be connected to are grounded by the lightning protection system.

There are lots of things that "work" but aren't really safe. Proper grounding is a safety feature. Ignoring it is like chambering a round in a M1911 and then putting it back in your holster with the hammer still back and the safety off. You probably won't have an accidental discharge ...

Station Grounding

by K6XR on August 17, 2004


Thanks for a very good article Steve, I totally agree on both topic's, swr and grounding. My station operation is similar to Steve's and I do not use an external ground rod outside the shack for any type of grounding. Everything works well from qrp to qro.

Station Grounding



Another huge falacy is the belief that RF grounds are not necessary if ....blah.....blah....blah.....Hams that run high power will find RF in everything in the house from low levels to very high and noticeable levels. RF can reenter your shack though any kind of wiring like cable, 240ac power line, AC grounds,even pipe near ground level, etc. Why? Because RF is induced into all wiring near an antenna to some extent. If there are no RF grounds, then the RF will just continually float. It has no path to ground by definition and thereby can cause all kinds of weird potential problems.

And if all you no RF ground type hams would actually put even a poor RF ground into your shack you will probably find the noise in your receiver much lower.

W4UDX style lightning protection

by W4UDX on August 17, 2004


I always keep an eye on the weather. If a storm is approaching, I take the following steps:

1: Shutdown equipment and disconnect all power cords from AC mains.

2: Disconnect phone lines from wall jack to protect modems, phones, etc... (this is the path in which most computers are damaged by lightning).

3: Disconnect antenna coaxs and stuff the ends into a heavy duty Mason jar located away from the operating desk(except the one that goes to the antenna tuner, rig, etc... leave that one out of the jar).

4: Use battery powered equipment with indoor antennas (like J-poles) to communicate with weather nets.

This will effectively isolate all station gear from lightning. I also do this before leaving for vacations. The only way my rig will get blown out by lightning is by a direct strike to the radio. If that happens, someone is sending me a message and it is time to give it up anyway!

Station Grounding

by K8AG on August 17, 2004


Not a bad article Steve but there is one reason for having a decent ground to a transmitter, cheapness. Not having a good RF ground for a transmitter can result in high RF voltage on some bands etc. This roduces a significant ouwee on my fingers as I key the transmitter from a device on the transmitter "ground". I am simply too cheap to buy an artificial ground and I find a 1" braid to a ground rod to be much cheaper and has no moving parts.

SWR (actually reflected power) is more important for the solid state radios than the tube radios many of us started with. Heck my first transmitter runed up into a lightbulb and simply connected to an antenna that probably was no where near 50 ohms. We can spend hours trimming and adjusting our transmission lines for absoulte minimum SWR, or we can spend the time operating our station.

73,

JP, K8AG

RE: W4UDX style lightning protection

by WB2WIK on August 17, 2004


I don't reply to people who don't identify themselves, so can't respond to some of this.

Regarding using an amplifier as an antenna tuner: This applies to tube-type amps, which all of mine are. Most all commercial (and all of my homebrew) tube amps have fairly wide-range matching units built in, although they are normally set up for an unbalanced line, like coaxial cable. The typical "pi-networks" and "pi-L networks" used in most HF tube amplifiers are there for one purpose: To transfer power from the tubes to the load. They are tunable. If you can transfer power efficiently and within the tuning range of those networks, you're done.

My own amps (all seven of them, including the VHF ones) can transfer as much power into a 2:1 or 3:1 mismatch as they can into a perfect match; as such, the tubes don't dissipate any more heat than they would, for a given output power, if the load was a pure resistor like a dummy load. If this can be accomplished, and with tube amps it usually can, there's no need for external tuners or matching networks.

I do use a high-powered tuner occasionally, for an end-fed wire antenna, or for balanced line fed antennas, or to use an antenna that very badly mismatched, e.g., an antenna not intended for use on the band where I'm using it. Those, for me, are rare situations that occur most often in "the field," and not at home.

The "high end" solid state amps like the Quadra have internal automatic antenna tuners, alleviating the need for an outboard one unless the antenna is an unusual load, as discussed in the paragraph above.

WB2WIK/6

Station Grounding

by ON4MGY on August 17, 2004


Great article from a great ham. I think Steve is one of the most active elmers here on eham and he seems to know just about everything you want to now. I just don't know where he gets the time to use his ham-equipment from time to time(hihi). Many thanks Steve and keep up the good work.

73

ON4MGY Nic


by G7HEU on August 17, 2004


Ditto what Nic said.

Steve M0HEU / G7HEU


by W6TH on August 17, 2004


Station Grounding.

Ground your radio and don't leave home without it.

Run a ground lead wire to each and every ham electrical device, then rest at ease.

Ground your radio and don't leave home without it.

AC/DC radios back in the old days were grounded to the 120Vac lines through a capacitor. Underwriters Labs, required by law.

Back in the old days the finals contained the Pi-network and had no need for a tuner and no need for the VSWR as the network was the tuner. We did ground all of our radio equipment in the old days, whether needed or not.

Our receivers were grounded as some signals would develope a 60 cycle buzz and the ground would eliminate this buzz.

I could mention much more, but will keep my notes short. My ham time of 66 years, from 1938-2004.

Nice article Steve, thanks for your time.

.: W6TH


by KC8SBV on August 17, 2004


Wonderful!! Keep up these wonderful instructive articles. They are awesome! Super Elmer indeed!

Station Grounding---Good Article

by TG9AKH on August 17, 2004


Congratulations on a nice, well argued article.

Your point is well taken---certain types of ground are either unnecessary or redundant. Additional "grounds" sometimes only increase the redundancy level of the already unnecessary. Yet, you left open the possibility that under specific circumstances, grounding may serve a useful purpose.

Perhaps your recommendation boils down to the need to use sound judgement, to know *when* those special circumstances have arrived.

This issue with redundant station grounding reminds me of the "all knobs to the right" attitude (disclaimer--I was once Mr. All Knobs to the Right myself). By this I mean that tendency to max out everything in a rig: max rf gain, max NB, max NR, max mic volume, max compressor level, max power output, max *everything*. I guess a logical step would be *max grounding* (?) Is there a knob for that?

WIRELESS: You made some interesting points in the beginning of your comment. Later, you started using words like "stupid", etc. I forgot about your points, the only thing I remember is that you used the word stupid. I guess that's what you wanted.

Station Grounding

by OBSERVER11 on August 17, 2004


re your stereo grounds.

There are only three grounds (same contact points, different connectors) on a stereo system... one is for your AM antenna, if you use a long wire, you get a ground point, one is the FM terminal for those that use coax, they provide you a point to screw the shield down, and the third is the most important for lovers of antique records. Turn tables must be grounded to prevent/reduce 60cycle hum.

So if you do not listen to AM, do not use a central antenna for FM and have gone CD, then there is no need to ground the stereo.




W6TH, I haven't been a ham 66 years, but I have been one almost 40 years and in "the old days," for me, I never grounded anything inside my shack. Antennas and towers outdoors, yes. Equipment chassis indoors, no. Never saw any reason to do so, and still don't.

As for the "grounded by a capacitor" for the old AC-DC radios, and "Underwriters Laboratories, required by law..." this doesn't make much sense. A capacitor coupled ground is not a ground. Every item we have with a metal case or chassis is capacity coupled to earth in some way, it's only a matter of value. Is .01uF sufficient? How about 1uF? How about 10 pF? Nah.

Underwriters Laboratories is an independent product test laboratory with absolutely zero ties to the government or to any legislation. Because U.L. prescribes something as a standard doesn't make it law; never did, still doesn't. An even older product safety test and recognition organization (than U.L.) is VDE in Germany. They don't make any laws, either.

You might note that the ring voltage on a telephone line is potentially lethal but telephone equipment carries no U.L. recognition. FCC Part 68, yes. UL, nah. Doesn't need it, never did. AT&T protested the UL monopoly 50 years ago and all the Baby Bells that emerged after their divestiture carried on in that tradition.

I do have substantial experience in this area.

WB2WIK/6

RE: W4UDX style lightning protection

by WILLY on August 17, 2004


As usual with WB2WIK's articles, a very well written, easy to read piece. Lots of food for thought. Thank you for taking your time to do it.

Is it possible, since we live in a world where everyone is ready to sue anyone they possibly can, that the equipment manufacturers are providing themselves an escape, should a user receive a shock? Along comes the user to sue, and if the manufacturer can find ANYTHING about the use of the ground lug that does not comply with their instructions - viola`, they can get out of the suit. This may not be the main reason for the lug to be there, but it is interesting to consider.

"My own amps (all seven of them, including the VHF ones) can transfer as much power into a 2:1 or 3:1 mismatch as they can into a perfect match; "

How does one go about measuring this?

I'm thinking that it requires more than a typical watt meter. Wouldn't it also require a watt meter that measure reflected power? You are comparing the two readings and finding them to be equal?


by WILLY on August 17, 2004



"... And if all you no RF ground type hams would actually put even a poor RF ground into your shack you will probably find the noise in your receiver much lower. "

WIRELESS,

In your opinion, what makes an excellent RF ground? a poor RF ground? Please describe each, and an example of constructing them.

Tnx


by KE4MOB on August 17, 2004


3: Disconnect antenna coaxs and stuff the ends into a heavy duty Mason jar located away from the operating desk(except the one that goes to the antenna tuner, rig, etc... leave that one out of the jar).

The jolt coming down your coax has traveled thru a couple of miles of air. How is 1/4" of glass going to stop it? I definitely wouldn't want to be in the shack when lightning does strike! Can we say shrapnel??

Plus, I think this might be the worst thing to do. My reasoning is this: by placing your feedline in a jar, you are not allowing any static charge to bleed off. Your antenna becomes a flashing neon sign to an oppositely charged cloud saying "strike me!! strike me!!"

I think the best thing to do is have the feedlines directly attached to ground during a storm. That way, the charge bleeds off and in the event of a strike, the lightning won't have to go down the feedline, through the jar, across the room, and *then* try to find a path to ground.


by K4JSR on August 17, 2004


Steve, you forgot about when your parents would "ground" you in your younger days! ;-) Also you evidently avoided "ground loops" with your aero-plane! I use an 8 ft. ground rod and common point grounding on my station just because I "feel" better about. No valid technical reason other than when I use my 135 ft dipole as a center fed "long wire" on 160. Even then I am dubious as to any benefit, but that is also why I have a 4 leaf clover in my shack.

I can remember when I was a mere lad and was being Elmered by Bubba Borne, W4ZD (SK), going outside of his (literally) shack to get a drink of water from hose spigot just outside the door. As the water flowed from the spigot and the ground, and my shoes, got wet the faucet would come alive with electricity and leave me doing a souped up "Teaberry Shuffle"! Bubba, and other adults would just hoot and laugh at my plight before rescuing me. Bubba would then try to get me to explain how a water pipe coming straight up out of the ground could do such a thing to me. Naturally, being a youth of just 12 I was totally baffled by the phenomena. Bubba finally explained that the water pipe was laid in the same trench to his shack as his AC power line. The water pipe had oxidized sufficiently to insulate itself from the ground and pick up some high (fortunately for me!) impedance coupling to the power line. He also taught me that when he turned everything off in the shack that the problem would go away. He was able to teach me a lot about the effects of current flow, and other marvels of electronics. I miss him! The moral of the story? All that glitters is not gold. All that appears grounded ain't! Thanks for giving folks the "dirt" on grounding.

73, Cal K4JSR "YIPE!", Ga.

Station Grounding

by WA0ZZG on August 17, 2004


This is interesting how much variation there appears about grounding. I'll pass along what I have learned from working with commercial towers and microwave systems. 1. Never directly ground radios. All that does is attract lightning energy to the radio. 2. Ground antenna systems at the tower base, the building entrance, and at the radio connection. 3. Make sure the radio can only 'see' one ground system. Never put a radio in a loop between two different ground points. Most equipment is not damaged by a direct strike, but by a nearby strike and the resulting surge energy looping from one ground system to another. Include the power company ground in this. 4. Go find what polyphaser means. It's expensive, but worth it. 5. It fun when you are standing next to the owner, have a direct strike on a tower, and nothing happens. Dave...

Station Grounding

by N6TZ on August 17, 2004


RIGHT ON STEVE!!!!

Grounding is such a mis-understood topic, and you will have many nay-sayers to your essay.

Just yesterday, I was discussing this with a friend who had put a ground rod in the yard and ran a wire upstairs to his 2nd floor equipment. He is feeding a dipole with a balun and coax. I suggested that upstairs, he should consider not only disconnecting the ground wire from the yard (it does absolutely only trouble), but also putting in a two wire AC plug adapter and abandoning the AC green wire. I doubt that these ideas were accepted.

On the contrary side, my equipment is ground floor and 3 feet from my radial system outside. I run 4 inch copper strap from the radials thru the wall and to my station equipment which is all 2 inch strap star configuration ground....Why? because about 15 feet away on the back side of the house is my shunt fed tower pumping RF back into the room and into the electrical house wiring....Oh, did I add that my equipment AC plug does not ground to the green wire? Think about it.

There are reasons to think through these various needs. I thought I would throw two extreme cases into the brew.

If nothing else, remember that ground is not always ground, it may be an antenna.

Hal, N6TZ




To determine a matching network's (or amplifier's own tuning network's) ability to transfer power efficiently to loads of varying impedance, I use resistive oil-cooled (dummy) loads of different resistances, with thermocouples to measure the rise in the load.

I have loads at 20 Ohms, 50 Ohms, 100 Ohms and 200 Ohms that are commercial and pretty beefy and good to the low SHF spectrum, but homebrewed loads could work well on HF. The Calorimeters are all commercial (HP, now Agilent).

I've never seen an HF amp with a pi-net (yet) that couldn't deliver the same power into 20 Ohms, or into 150 Ohms, as into 50 Ohms.

Another way to measure this is thermal rise in the amplifying devices themselves, converting Calories to Watts and then subtracting that from DC input power measured the conventional way. If you have 1000W DC input and 500W dissipated in the tubes, what remains ought to be output power (500W) unless you have components in the plate circuit getting mighty hot.

If you make this measurement with various terminations, re-adjusting the network to accommodate those variations, and see any notable difference, I'd be very surprised.

Usually, you can tell if the amp's tuning network has sufficient range to accommodate your load: Output power will peak within the tuning range of the variable components, and the DC indications, including plate and grid currents, will be about the same as they are when using a 50 Ohm dummy load. If those two conditions occur, I'd bet dollars to donuts your amp is very happy with the load and delivering as much power as it would into a 50 Ohm load.

My 75/80m antenna has a bit over 3:1 VSWR at both band edges and I've never even thought about using a tuner to correct that. My 160m antenna is well matched at 1815 but about 4:1 at 1870 and I use it up there all the time (AM contacts!) without a tuner. The amp is my tuner, and if I can keep plate dissipation and grid current within tube ratings, it's very happy.

WB2WIK/6


by KC8VWM on August 17, 2004


I would be interested to know if any studies have been conducted from anyone that actually had lightning strikes.

For example, a lightning strike resulting in damage from a person WITH grounded station equipment vs. damage caused to a station without any station ground at all.

Fact # 1

Communication centers like police and ambulance dispatch centers operate during lighting storms.

Fact # 2

Same holds true for AM/FM and Television broadcast stations.

Cell phone tower antennas are not the only thing grounded at a cell phone tower site. The equipment is also grounded. Why not just let the equipment float?

What do these cell phone tower and other engineers know that we do not know?

Why do these places protect themselves from potential lighting damage? Should they even bother if the main antenna is already grounded?

Some argue this point, "Why provide a ground path inside your home for lightning to travel"

Why would anyone not think that the coax cable going into your home from your antenna is already providing that path? Station ground or no ground aside.

Therefore, I would ask:

Should lighting terminate at your station equipment, or do you provide the static electricity with a means of "escape"?

True there is not much you can do against a direct hit, however, why wouldn't you want to make some reasonable attempts to minimize any possible damage from occuring?

Here are some resources:

"Observations from Sandia Laboratories lightning testing (6.3) confirm that lightning exhibits radial horizontal arcing in excess of 40m. This ground surface lightning spreads according to local soils impedance characteristics, resulting in step and touch voltage hazards. Capacitive, inductive and ohmic attachment processes also come into play (6.4). Victims insulted while near trees, or touching electrical appliances, or in contact with water or other unintended conductors often are recipients of fatal currents and voltages after lightning strikes them indirectly."

Source:

http://www.lightningsafety.com/nlsi_lls/deaths_injuries01.html

"The potential increases on the earthing and on all earthed metal parts of the object relative to the zero potential at a distant point. It may reach a very high value but it does not cause any danger if the potential differences inside the object to be protected are limited. Potential equalization is realized by the bonding of all extended metal objects."

Source:

http://www.lightningsafety.com/nlsi_lhm/rtaf3.html

73

Charles - KC8VWM




Charles, some of this stuff is pretty irrelevant, if you think about it.

Commercial BC stations, at least for FM and TV, can have pretty poor grounds because they're located up very high above ground. For example, most NYC FM-TV stations are on the 82nd floor or above in the Empire State Building (espcially now since WTC no longer exists -- but when WTC was active, the transmitters were higher than that). This is almost a thousand feet above earth. Grounded? Hmph.

Most telephone equipment is low voltage DC powered (usually by 48v, with a positive ground) by batteries. Many of the cell sites I've been to (most of them, around here) do not have the equipment grounded to earth, but rather to the positive terminal of the battery bank. Whether that's actually grounded or not is another issue, but in many cases, it's not. That equipment is very well isolated from the AC mains, so a "safety" ground is irrelevant; and RF ground is meaningless at 800-2400 MHz, where you couldn't achieve an earth RF ground unless your equipment was buried underground.

Regarding data on lightning: The tower on Empire was erected 60 years ago before current standards existed. There was no code, all the lightning safety councils didn't exist, Polyphaser wasn't born yet...and transmitters have been operating there all this time, more than 1200 feet above ground, where for almost 40 years that tower was the highest point in any direction for several miles. Amazing.

WB2WIK/6

Station Grounding

by W5AOX on August 17, 2004


I am continually amazed at the quickness of some hams to immediately label someone like WB2WIK Steve Katz as "inexperienced", "naive", "ignorant", "doesn't know what he's talking about", etc. How long have you been publishing real-life technical articles in electronics magazines, Steve? I think I remember one from almost 20 years ago, on homebrew receivers. I've also been jealous of your experience, expertise, and success on the VHF bands both high and low power. I have been in the electrical and electronics field since about age 16 or so, and have tried both sides of the "Ground for Safety Etc." fence. I have experienced TWO direct or close-to-direct lightning strikes in my 20+ years of hamming with a tower pointing up to the sky. The first occurred while living in my brother's house in Carlsbad NM (a very active lightning area). We were sitting in the kitchen when the stroke hit the tower. The lights in the house turned almost double-brilliance for several seconds as the ground and house literally shook. When I opened the door to the garage where the hamshack was, I smelled smoke... and burning electronics.... a bad sign. All coax had been disconnected prior to the storm but lightning had flashed across the bench in various areas from the coax entry points to anything plugged into the wall. You could see the carbon-paths across the wooden bench. That tower was grounded, but it did not keep lightning from striking, and more damage occurred then than the second strike which hit at a different house some years later which was NOT grounded, other than thru the guy wires and base section of the tower. The tower in Carlsbad may have actually have saved the house from damage. When my non-ham brother lived there, 2 years before MY lightning strike, he had experienced a large lightning strike. His neighbor told him he saw the strike seemingly hit the garage. When he looked around in the garage, he could see little evidence of damage.... but he did notice an almost-straight line of spikes stuck up in the sheetrock ceiling of the garage. When he tried to figure out how they got there, he noticed a crack in the concrete floor just below the string of shards in the ceiling, and realized the shards were splinters of CONCRETE, literally blown into the ceiling from the floor when the lightning penetrated the roof. Upon close examination of the roof, he found, directly above the cracked concrete and shards, a small scorched slice in the roof. Evidently lightning had just SLAMMED its way through the roof and hit the floor..... avoiding the AC entry wiring and grounded conduit halfway across the room. I fail to see how grounding could have prevented damage from either of these strikes.... lightning is so unpredictable. I have often wondered if, by taking pains to ground our stations, we are not actually risking increased attraction for lightning strikes. I was once caught in a storm with frenzied lightning, hail, and thunder, and had to pull off the road right across from a 700' TV tower on my left. I couldn't see to drive further, but I noticed I could see the top of the tower through various holes in the storm, so I watched to see how many lightning strokes would hit it. I watched for several minutes, with lightning crashing all around, and NO visible strikes ever hit the tower. I looked around in other directions to see what WAS being struck by all the lightning, and was surprised to see most of the flashes striking OIL TANKS, short, large, and squat, with rounded tops, most of which were down in a small low part of the terrain. It seemed that the large surface areas of the tanks provided a very good grounding contact, and though the lightning had to travel much farther down to hit them, hit them it did, and multiple times apiece. I argued for an hour one time on 2 meters with a very vocal trucker-ham who had read prevalent literature (of course he was big on CB and associated literature) and was absolutely convinced the ground strap from the back of the mobile radio was necessary to form a good RF GROUND, in spite of the fact the feedline was coax, grounded both at the radio RF connector and the antenna feed point. When people have deeply held beliefs that they have not researched for themselves in "real-world" experience, it becomes like a religious belief..... it matters not that you may have years of experience in RF and AC power, you must just be a lucky dummy since you don't realize the TRUTH that was published SOMEwhere........ I would only disagree with your faith in the grounding via the AC outlets. Test them first, then trust them. I once was trying to install a base station for a customer who was a LICENSED ELECTRICIAN. Every time I plugged in the power cord, the circuit breaker would trip. Turned out the AC outlet had the HOT and NEUTRAL lines reversed, and when the base station was plugged in, grounded through the coax and antenna pole, it shorted the AC mains and popped the breaker. Glad I wasn't the long path between the "chassis ground" and the coax before the breakers started popping. At Los Alamos National Lab, we found we could NEVER trust an AC outlet; we had to check them all before plugging in equipment, even though all electrical work was done by union / licensed electrician tradesmen. They seemed to never wire outlets the same way twice. So, though I agree "grounding your station and indoor equipment" is overblown and unnecessary (you must have a THICK skin to bring this subject AND SWR into the same article), I scream aloud: DON'T trust your house wiring (especially for safety grounds) until you've tested it!




""Underwriters Laboratories is an independent product test laboratory with absolutely zero ties to the government or to any legislation. Because U.L. prescribes something as a standard doesn't make it law; never did, still doesn't. An even older product safety test and recognition organization (than U.L.) is VDE in Germany. They don't make any laws, either""

What the Underwriters Labs has to say directly influences the National Electrical Code, and with it, local electrical inspectors, home inspectors, and insurance adjusters. What they say is followed by the NEC, and is the deciding factor in any legality when it comes to electrical grounding, and station grounding. Period.

National Electric Code is what we should be referring to here, not UL.

I am enjoying this discussion. I like a person who is opinionated because he knows things... not because he thinks he knows things. Bravo, Steve.

Station Grounding

by NC2W on August 17, 2004


The prevelance (or lack thereof) of lightning strikes should never be a VALID reason to (or not to) ground.

SWR is almost never a problem in tube rigs. They simply disappate the reflected power as heat.

SWR in a modern rig, with transistored finals CAN pose a problem. Power reflected back to the finals, as heat can ruin a transistorized final.

Station grounding is not a panacea for trying to make a current type antenna out of an antenna acting as a voltage device. Having typed that, I'm not sure anyone said it was.

The purpose of a ground, is make an electrical connection between 'GROUND' and the chassis. Such a connection is required by NEC (Article 250.110 -250.114, and Article 810.20). No more, no less. To suggest grounding is wrong, or unnecessary is incorrect.




W1CAR: UL may influence NEC, but the two aren't directly related in any way. Actually, UL1950, the standard for most of the electronic equipment we use daily, has been revised to UL60950 in accordance with European standards developed independently of UL by IEC.

Also, there is no requirement anywhere in America (or anywhere else) for equipment to be UL recognized. This is a voluntary thing, and lots of electronic equipment is not UL recognized, nor recognized nor certified by anybody. There's no law stipulating that it must; although in some cities, local Fire Ordinance requires that electrical or electronic equipment actually connected to AC mains for demonstration or sale must have an NRTL (like UL, or similar organization) or Fire Marshall tag clearly displayed on the equipment during such sale or demonstration.

NC2W: What can I say? If you believe reflected power is dissipated as heat in the power amplifier stage, you have it all figured out.

Golly!

WB2WIK/6




"W1CAR: UL may influence NEC, but the two aren't directly related in any way"

Thanks for the clarification. But, isn't that what I said?

Station Grounding

by WA2KWP on August 17, 2004


Steve,

I really like the way you write and your choice of subject matter. I wish, however, you hadn't couched your article in the guise of an old wive's tale. The grounding issue is technically well known. The problem with your premise is that grounding is never necessary. It is in fact 'sometimes' necessary. It is difficult to know when. It would therefore seem prudent to ground as much of the installation as possible to cover yourself. As technology improves it may be possible to "ignore" grounding.

I don't believe you can mix the terms earth and ground. We should also not confuse the two terms, as each has a definite meaning. I believe the technical concept is that earth is a path for current to the earth, and ground is a common reference level for all elements.

About SWR. I remember from 55 years ago, as a young novice, extensive talk about SWR!! SWR was a concept well known to Hams of that time, and cause just as much conversation as it does now. Although true that there were no inexpensive pieces of equipment for measuring SWR with a number, there was a simple method of viewing SWR. This was to hold a florescent bulb against the twin lead transmission line during transmission. Not only could you load for maximum output by the brilliance of the tube, but you could actually see the Standing Waves marching up the tube!!!

I wonder if you are old enough to remember the Army training movies showing the soldiers marching up and down the transmission line representing Standing Waves. I also remember the "old timers" of that period saying that SWR was only one of the factors to be considered in design of an antenna, not the only factor. I believe they understood the concept very well then, just as most knowlegable amateurs understand it now. Although SWR was a mathematical concept; the numbers 4:1, 1:1 to represent SWR were common in conversation, and well understood, although essentially only theoretical. I don't remember seeing an SWR bridge until the early 60's, and didn't own one until Heathkit put one in their catalog. At that time I really didn't believe you needed one.

Keep up the good work. You are an asset to the understanding of Ham Radio Theory, and the Ham Radio Community. David WA2KWP




W1CAR, yes, it is, although you went on to imply (I thought, at least to me) that UL has a strong influence on NEC, and that somehow UL will be influential in liability issues concerning grounding, should those arise. If I interpreted that correctly, I disagree with that premise.

UL representatives won't even testify, as far as I know, and are never an arbitor that I've ever heard about.

There was another claim in here, somewhere, about NEC requiring some specific method of equipment chassis grounding, which it does not, for any consumer electronic apparatus. Many consumer appliances still have 2-wire power cords and plugs, including some mighty powerful ones. Check your toaster, or your hair dryer, for example...

WB2WIK/6

Station Grounding

by NA4IT on August 17, 2004


Good article! But an old gentleman told me how to keep my rig from getting hit by lightning:

(1) Unhook rig (2) Place in styrofoam and original box. (3) Place under bed

(Just a light hearted look at grounding!)


by W6TH on August 17, 2004


Confused are you?

Ground is a common reference point in the radio circuit. "Ground Potential" means that there is no "difference of potential", no voltage between the circuit point and the earth.

The use of tube amplifiers in general practice is to ground the negative terminal of a dc power supply and to "ground" the heaters or filament for vacuum tubes.

There are ground and ground potential. When a connection is said to be grounded it does not necessarily mean that it actually goes to earth.

We need more theory on this subject and find what a ground is really all about. We may all have grounds and do not realize it.

.: W6th




NC2W, I did look up your NEC references 250.110-250.114 and also 810.20 and to refer to these in response to this article is really a stretch. The 250.xxx sections refer to proper grounding of electrical outlet boxes and 810.20 refers to grounding of satellite antennas and such.

This whole article is about "equipment chassis grounding," using the ground terminal on the rear of your equipment chassis -- which NEC makes no reference to, anywhere, in anything. Ham gear is "indoor consumer electrical and electronic apparatus" by definition, and is not regulated by code.

W5AOX: Thanks for the comments. It's been a lot more than 20 years! My first technical articles published were in 1970, when I was 18 years old. I've been on a bunch of IEEE committees over the years and that was kind of fun, but it sure can get tiring working with groups of individuals who can never agree on anything.

WB2WIK/6


by KC0LET on August 17, 2004


I just wanted to comment on sticking the ends of your coax in the mason jar. I have to admit I do that too. I don't do it to prevent lightning strikes or anything like that however. I will also mention nothing in my shack is grounded except for the safety ground provided by the third prong on the power cords.

Anyhow, I have a lightning ground system, with surge protectors in the coax lines, connect to a ground rod system that is also bonded to the tower. All of this system stays outside - you want to channel the lightning into the ground before it enters your house. Anyhow, I put the coax into a mason jar after an experiance a friend of mine had during a lightning storm. He had his coax unhooked and laying on his bench. He didn't have any surge protectors inline. With each nearby stroke of lightning, you could see a spark arc from the center pin of the PL259 to the outside barrel. Ever since then, he has advocated the use of a mason jar to prevent a fire in the shack.

Last summer I was in my shack disconnecting my coax during a thunderstorm. I had just finished and had turned and started walking out of the room. I had gotten about six feet from my bench when I was knocked to the floor by a very loud explosion like noise. Lightning had struck between my tower and the house. The tower is about thirty feet away from my shack, so I was only about fifteen feet away from where the lightning hit.

I suffered no ham equipment damage, except for the Radio Shack NOAA weather radio that was on my desk, and my computer network hub. The indoor antenna on my weather radio was nearly burned in two. My shack is in the basement with a false ceiling. One of the metal pieces that make up the support grid for it had a hole burned in it...it was still warm several minutes after the strike...explain that one...I still haven't figured it out, there are no wires running anywhere near the spot the burned.

Also, I have a furnace vent in the middle of my ceiling connected to the metal ductwork of the central heating and cooling system. The screws were burned out of the register. I really should take some pictures and post them.

Just a little reminder of the power lightning contains.




W6TH, we have to meet for an "eyeball" one day and swap war stories about SSME and other space programs. I consulted to Rocketdyne ISD (Chatsworth campus) on ISS, on the SS Freedom power conversion designs, in concert with Boeing, Lockheed and Loral (at that time).

What a circus! But I'm sure you have some stories, too...

WB2WIK/6


by AA4PB on August 17, 2004


Very good article. In my opinion, the one ground that is important (other than the electrical system safety ground) is grounding of the coax just outside where they enter the house. That is only for lightning protection. Disconnecting the coax cables and leaving them lay on the floor or sticking the ends in a mason jar may save your equipment but it is not likely to save your house. Actually it may not save your equipment unless you can get it out of the fire quick enough :-)

Other than the lightning grounds and electrical safety ground I have also never used a ground connection. Unless your equipment is setting on the ground it is usually pretty difficult to get a good RF ground to the rig anyway. If your antennas are properly balanced and located far enough away so that they won't couple RF into the shields then an RF ground is not needed.


by K0IMJ on August 17, 2004


Steve, thanks for saving me a lot of trouble. I have been a ham for 47 years and really never grounded my rigs. That was my next BIG project. Being on the upstairs floor provided me with some problems, and delayed me from doing what I thought should be done. Now I am rethinking once again. I have quite a few tube rigs (www.heathkits.com) and I notice that when I record the lowest SWR for a solid state rig and then set it (the ant. matcher) the same way for a tube rig...sometimes the SWR is higher, or at least different. Would you write a COMPLETE article on SWR. I am one of those guys that is starting to realize how much I don't know. Thanks and keep up the good work. Gary K0IMJ (www.heathkits.com)

Station Grounding

by W8JI on August 17, 2004


Station Grounding Reply by K8AG on August 17, 2004 Mail this to a friend! Not a bad article Steve but there is one reason for having a decent ground to a transmitter, cheapness. Not having a good RF ground for a transmitter can result in high RF voltage on some bands etc. This roduces a significant ouwee on my fingers as I key the transmitter from a device on the transmitter "ground". I am simply too cheap to buy an artificial ground and I find a 1" braid to a ground rod to be much cheaper and has no moving parts. >>>

I agree 100% with Steve. If your antenna system is properly designed and constructed and your equipment is designed well, there is absolutely no need for an RF ground in the station.

An RF ground is a band-aid for other more serious problems.

The exception to all of this is if you intend for your equipment and everything in and connected to your operating position to be a part of the antenna system, or if you have an antenna extermely close to station equipment.

For information on why stations have "RF in the shack", have a look at:

www.w8ji.com/common-mode_noise.htm

www.w8ji.com/verticals_and_baluns.htm

http://www.w8ji.com/end-fed_vertical_j-pole_and_horizontal_zepp.htm

Fix the antenna system, and the RF in the shack will go away.

73 Tom




Anyone who thinks amplifiers dissipates reflected power as heat needs to review how amplifiers convert DC into RF.

http://www.w8ji.com/Vacuum_tube_amps.htm

"Reflected power" may make an amplifier run hotter or cooler if the tank is not retuned to match the new load impedance. If the tak is retuned, Steve is exactly on target. It makes no difference at all in ANYTHING except the current flowing from the tank to the output connector and voltage across the loading cap.

The tubes have no idea if the output mismatch is 1:1 or 100:1, as long as the tank circuit matches the load impedance. The normal range of a tank is 25 ohms to over 100 ohms, and is generally more restricted on bands like 160 and less restricted as frequency increases.

The oldest and worse myth is reflected power hurts the life of PA tubes.

73 Tom

Station Grounding

by KB9YGD on August 17, 2004


Well You Can Allway`s Tell The ``NO GROUNDER`S`` On 75 With All The RF In Their Audio.Also You Ground Stuff And All The Voltage`s That Like to Bite UR Lip Or blow Out The Little Bulbs In The Tuner,Etc Are Tamed.And At HF The Ground System Is A Big Part Of The antenna System.73,``THE REAL HAM``

Station Grounding

by WA2JJH on August 17, 2004


Great artical! I have always maintained a good station ground since I got zapped I learned this the HARD way 30 years ago.

I could not understand why when I touched my TS-520 and the sheild connector of the PL-259.

I got huge zap. I then learned about ground looping, floating grounds, and chassis ground.

I once measured a ground differential of 80VAC! Try this for fun. Hook up an AC voltmeter between your rigs GND stud and the outside of a pl-259 that is your antenna's ground at te other end of the feed.(Cable not connected to rig) Do not be surprised if you do not see 0 volts!

I work with signals/equipment that statistical anaylsis are needed to see what is the output vs guassian and poisson noise. Common chassis ground for all test equipment must meet very strict standards.

Have fun and be safe. A fringe benefit of being safe might get you to receive DX better!

Station Grounding

by K3YD on August 17, 2004


I have to mention a time when I found radio grounding necessary. I was operating CQWW-CW at an east-coast contest Multi-Multi using a new radio which relies exclusively on DSP for selectivity. In this high-RF environment, using an(ungrounded) transceiver, received CW was un-readable. The signals from 3 adjacent KW stations, combined with the strong signals being received on a 6-el Yagi were mixing to create something which sounded like CW sent by left-footed gorillas sending Japanese using the Cyrillic Morse alphabet! I first inserted an ICE bandpass filter between exciter and amp, but that did little. However, as soon as the transceiver was connected to the station's ground-buss the insane mixing stopped and I could operate. There are probably other solutions to the problem, but when a contest is 17 minutes old and 20 meters isn't producing, you grab at anything which works.




Reflected power *does not* hurt the life of PA tubes?

Oh, crap, now I have to go digging in the trash to retrieve those 8877s :)

One respondant asked about tuning antennas without using an SWR bridge. This can surely be done, but in year 2004, I'd have to ask "why bother?" A decent commercial SWR bridge costs very little and is a great station accessory/test instrument that every ham should have -- now. My comments regarding this were attempting to point out that in "olden" days (not all that olden), many hams didn't own such instruments and somehow worked the world, anyway.

In many cases, they used antenna tuners and just tuned for maximum feeder current. A simple diode detector field strength meter could also be used to just tune for "maximum" indicaton, whatever it was, as long as the detected RF was coming from the antenna and not from the transmitter itself!

Then, many never matched their antennas at all and simply tuned for a plate current dip on their PA stage. That should correspond to about maximum output power, if the stage is properly loaded, and as long as you're running "maximum," who cares what that really is?

I'll admit as a Novice, and lacking an SWR bridge myself, I used received signal reports to affirm I was getting out about the way I thought I should. Every "599" report was such an affirmation!

WB2WIK/6

Station Grounding

by WA1RNE on August 17, 2004


Wish I could I agree but there are at least 2 very common situations where connecting all equipment together to a central station ground is the safer play.

First, we are human and we make mistakes. Some are painless, some can be deadly or result in an RF burn, which hurt like hell.

Here are the 2 situations. I'm pretty certain that over my 30 years in HR, I'm not the only one that has made them: (Of course, some hams have better track records than others)

1) Running tuned feeders without a station ground;

If one leg of the transmission line fails or breaks, you now have a whopper of an unbalanced feed line and a high SWR to boot. The potential is high for some hefty currents floating around the shack, especially at 1.5 KW PEP. I would rather have my rigs at a lower RF impedance than becoming part of the voltage side of what is now potentially a multi-wavelength vertical antenna!! Anyone ever see/use that cheap ladder line with #16-20 solid conductors? Some homebrewed versions use soft drawn copper that can snap after being in the wind long enough.

2) Running older Boat Anchor vintage equipment along side of newer vintage gear;

Prior to approx. 1975 or so, most transceivers, receivers, transmitters, etc. were not equipped with a safety ground on their input line cords. Relying on the coaxial feedline to ground these rigs can be dangerous - especially if you decide to switch antennas manually or switch to a tranverter for VHF, etc., etc. Most people don't think of pulling the line cord just because they're tinkering with a coaxial antenna cable.

Summarizing, it's both good practice and in most cases inexpensive to run a station ground and can help prevent some unpredictable types of events - keeping you on the safe side of things if they do occur. I've been doing it for 30 years and haven't had a problem - unless of course I forgot to reconnect it.


by AB5XZ on August 17, 2004


A friend recently remodeled a 1914-era home. The first electrical contractor (later fired) forgot to ground the electrical system. Symptom: alarm clock advancing at about twice usual speed. Once the ground was established, that problem - and some others - went away.

Moral: you can get away with it (no ground) sometimes, but you should really understand what you're doing and why.




I'd like to add one more comment that is life and safety related.

While I agree strongly an RF ground is not required unless the station is intentionally or unintentionally part of the radiating antenna system, I just as strongly disagree with advice station equipment with ground lugs should not be grounded to a common safety ground.

Worse yet while reading through comments I saw a suggestion of floating the third wire of a grounded cord!!! NEVER float the third wire of a grounded plug!!! It is there for a good reason.

Line operated equipment with ground lugs should indeed have lugs grounded to a common SAFETY ground. It is poor advice to suggest we NOT ground equipment to a safety ground.

Ham equipment is different than conventional consumer devices like toasters. Toasters and other appliances are extremely well-insulated. They do not contain line bypass capacitors for RF filtering. They have well-insulated switches, and long intenal arc-paths. They don't have rear panel jacks that connect to the frame and allow other appliances to plug in.

Amateur equipment is very much different. It often contains large bypass capacitors, sometimes larger than .01uF. There is complex wiring, and much of it has minimal insulation to the chassis. There is often HV inside.

The Ham station is also very much different than a living room or kitchen. The Ham shack has wiring that runs outside, it has interconnecting wires that run between different pieces of gear. If a component fails and that particular piece of gear has a high resistance to safety grounds, you can be be killed. This can happen when you are reaching behind a radio to screw in a coaxial connector.

NEVER float the equipment to separate grounds, and especially NEVER remove or defeat grounding pins on cords!

Let's look at a vacuum tube power amplifier. If the HV supply is 3000 volts, a single common component failure can place 3000 volts plus 170 volts on the chassis if the chassis has no ground path to a safety ground!! Where is that failure? From the high side of the secondary of a supply to the primary winding high side of the power transformer. Without a chassis ground path, the chassis will come up to line voltage sinewave peak (a typical maximum of 170V)plus voltage between the hot end of the secondary and chassis of the amplifier. The ground path would be all that would cause a fuse to blow!

Only an suicidal fool would remove or defeat the third wire safety ground of an amplifer, or float the chassis from a common safety ground backup.

There are a lot of components that can fail and cause big problems. Say for example you have a slightly loose coax connector and no short common ground connections between your gear. All of that RF normally returning harmlessly on the inside of the shield now flows through whatever RF path it can find.

That path can be sensitive and expensive equipment. While an operator RF burn might heal, and IC chip is gone forever.

While I agree an RF ground is a sign of other more serious problems, a common ground in the station that has a path back to the power line safety ground is ALWAYS a good idea. The third wire of a power cord should NEVER be remove or isolated. Our equipment should always have a common ground, especially if high power is used.

We do not need a good RF ground in the shack if the antenna system is well-engineered and properly installed, but it is a serious safety issue for people here to suggest floating equipment is a good idea.

Don't worry about the RF ground if you have agood installation, but by all means make sure you have a common ground that is bonded to the power mains safety ground. Not doing so is just plain stupid.

73 Tom


by AA4PB on August 17, 2004


Well You Can Allway`s Tell The ``NO GROUNDER`S`` On 75 With All The RF In Their Audio ------------------------------------------ Or perhaps the guys who are running a KW with the antenna directly overhead.




I was rather surprised to read about anyone defeating their "third wire" ground, and was wondering if that was tongue-in-cheek or for real.

Nowhere did I ever imply equipment shouldn't be grounded. My article addressed adding "more" grounds, in addition to the standard safety ground already provided in an engineered station.

Of course, I could tell you all about an accident I had many, many years ago when I had a medium-tension (7200V) power line fall across the element of my 20 meter beam (seriously). I had no auxiliary station grounds of any kind, but everything was grounded, anyway, and here's what happened:

7200V line fell on antenna and just hung across it. Came into the shack the next morning to hear a peculiar humming sound. It sounded like it was coming from my HF amplifier, but couldn't be certain.

I felt the amp, it was cold, but really did sound like it was humming (like a transformer lamination problem). So, I unplugged the amp from the 240V power line, and the humming stopped. What the heck could cause that? The amp was "off," of course, even before unplugging it.

I felt the AC power cord between the 240V wall outlet and the amp, and it was warm. What-?

I started feeling other stuff. The coax cable from my 20 meter beam, where it plugged into the station coax switch, was also warm.

The path from the HT line to ground was through my coax, the coax switch, the patch cable between the switch and the amp, then through the amp and its power cord, into the 240V outlet. That was the path, and it was conducting considerable current, which is why everything in the path was warm.

I went outside and looked "up" and saw the cable laying across the beam element. I wondered, "Why doesn't the return path go through the tower?" and then remembered this was an isolated-feedpoint beam with no return of any kind to the mast or tower, and my only balun was a coil of coax, used as an RF choke.

So, this is one example of something that could have been a pretty bad scene, saved by ordinary coax and 4-wire 240V power cord. I never did figure out what the humming sound was, but after having the power company shut down the line and replace it (which they did in less than two hours, once I called them!), the hum never recurred.

I wonder how much current it took to get the RG-217/U that warm? Probably quite a bit....

WB2WIK/6

NEC Quoters

by K0BG on August 17, 2004


When I first saw Steve's article (please note the correct spelling of articleit isn't spelled artical!) this morning, I thought just like Steve did in his last paragraph (the title therein)let the flames begin!

A lot of the flames quoted the NEC (National Electrical Code) as reasons for or against proper grounding (or lack thereof). I have this to say:

Before you quote a well-known (and accurate) source, you best have read it at least twice, and preferably several times and know EXACTLY what it says. Steve's article was intended (I'm sure) to separate fact from fiction. Unfortunately, the very information Steve used to document his position was (has) been misquoted and misconstrued to suggest an alternate view.

For those who disagree and quote the NEC, go read it again, several times!

Alan, KBG ww

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