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[Articles Home]  [Add Article]  

From the GROUND up

from Dale on December 21, 2000
View comments about this article!

Working from the GROUND up  

for a Good HAM Station

A good ground is one of the most essential parts of a good HAM station. There are various reasons for this statement. First and foremost is for the safety of your family, home, and HAM equipment. Lightning NOT ONLY KILLS HAM radios but often starts house fires - jeopardizing the safety of your family! A protruding antenna or tower into the atmosphere dramatically increases your odds of a lightning strike. Statistically however, most lightning damage comes from the AC power or telephone lines running into your home.

An understated fact of significance to HAM Radio is that a good ground WILL increase receiver sensitivity and transmit propagation. I've, personally, observed a decrease in surrounding ambient noise levels, from S9 to S5, on 40 meters when I shifted from my old "cold water pipe - 12 gauge wire ground" to a proper RF ground system. HF antenna(s) work BEST when they work against a proper counter-poise ground reference.

Good RF grounding is as mis-understood and as difficult to understand as phenomena of impedance. Both are very real, hard to measure, and cannot be tangibly seen in operation. The term that is used in RF grounding is "skin effect." In a ground system the majority of electrons run along the surface (or skin) of the conductor. A good RF ground has the least amount of resistance to electron being conducted to ground. This is obtained by having the most amount of conducting surface area, that is practical. The goal of a good RF ground system is to obtain as little resistance as possible from the antenna/tower to ground and the radio to ground. Thus the more conductor surface area the more ground path conductivity.

A good ground system measures less than 12W from radio to ground. Typical, cold water pipe grounds will measure >35W and that's if the water pipes are NOT PVC. Making this measurement is very difficult and most HAMs do not have a Megger instrument to make the measurement. Some education, a well planned out, and properly installed ground system is typically the best most HAMs can afford and accomplish. That's were this paper will attempt to assist you by giving examples of reasonably good RF ground systems that are within the economical range of most HAMs.

A few items need to be contemplated before deciding on how to install your RF ground system.

a. You need to consider your budget and the amount of effort that you are willing to give in installing a good RF ground system. It is NOT to your advantage to be too cheap and lazy - or you might as well just use the cold water pipe. Then be prepared to buy new equipment when you get your first lightning strike.

b. Dissimilar metals (as it pertains to electrolyzing/galvanic action) can pose a significant problem to the systems longevity and minimizing maintenance issues to your ground system. One rule is NEVER connect copper to galvanized or aluminum towers - use a stainless steal interface between the two metals with a stainless steal clamp, bolt, washer, and nut!

c. Copper oxide (the greenish copper corrosion) is NOT conductive! Eventually compression clamps WILL allow corrosion to migrate into joints causing a reduction in conductivity and increase the connections overall resistance. Weld or solder ALL joints, when possible, this will ensure long life and maintain stable good conductivity between connections! If a stainless steal clamp is used a conductive grease is required to minimize connection moisture degradation.

d. Eliminate ground loops and multi-point ground connections when possible. A HAM shack ground loop gives lightning another path to your equipment. Always use a single point ground between the interior and exterior of your HAM shack!

e. Run your coax/hard-lines to the base of your tower or antenna mast and directly connect to the coax/hard-line shield clamps to the tower/mast base. This will allow the lightning to get as close to the actual ground connection before attempting to enter the house. When creating a drip bend in coax/hard-line use a minimum radius of nine inches for the curves.

g. Grounds rods or other grounding pipes MUST reach below your local areas permafrost layer to remain active year around. You can easily find this level by checking your local plumbing building codes. Typically, in central Wisconsin the minimum depth is six feet. The ideal grounding situation is in having your ground system make physical contact with the water table, however, this is not very practical.

This document gives examples of two scenarios for a good RF HAM ground system:

First a house mounted antenna ground system;

(Note:  Click on any image to see a larger version -ed. )

Second a tower mounted antenna ground system.

(Note:  Click on any image to see a larger version -ed. )

 

Grounding Rods vs. Pipes

Due to economics and the effort required to drive rods I've taken another approach in lieu of rods. (Besides four foot rods are worthless as they do not make enough soil contact for an adequate safety ground much less an RF ground.) I use ten foot pieces of 0.5" copper PIPE fitted with a brass hose fitting. I purchase a brass hose fitting from a local hardware store and solder this fitting to the end of the copper pipe. This allows me to attach a garden water hose and easily hydra-drill the copper pipe into the soil. No mallet or "T" post sledge for me.

I dug a one foot square deep hole in the ground where the ground pipe is to be drilled. I drilled the pipe into the ground until the pipe top was 6" below the surface of the ground. This allowed working room to solder the copper tubing and then cover the hole making it invisible to all and your lawn mower.

Ground Conductor Copper Buss-bar vs. soft Copper Tubing

Again, due to the economics and availability of copper buss-bar material I found the costs to be prohibitive to a normal HAM's budget. Instead I use soft copper tubing that is easily obtained at your local hardware stores. The trade off is the amount of surface area the copper tubing will have in comparison to copper buss-bars. I highly recommend that you use ³ 0.5" copper tubing for short runs, i.e. £ 10', or as your budget will allow - but attempt to keep the conductor surface area high as near to 1.0" copper tubing as you can afford. Remember, the more surface area the better the ground conductivity!!!

I use soft copper tubing for practical reasons - ease of use. Where a soldered or clamped connection is to be made I hammer the tubing flat. Then using Vice-GripsÔ I wrap the flattened tubing very tight around the copper ground pipe/rod and make a good soldered connection.

The copper tubing is buried at least 6" deep. This will keep you from hitting the ground system with the lawn mower or becoming a trip hazard. The buried copper tubing is also part of the energy dissipating ground system. In using buried interconnect bare copper tubing the whole "ground system" conductivity can be increased when watering the lawn as the near surface soil conductivity will increase. A HINT during contesting.

Ground Plate

This item can be controversial to some as few HAMs want to mount or put a fair sized hole in the side of their house. The ground plate is a solid barrier to possible lightning entering your house via your coax/cables. Also this ground plate is the fundamental item that creates your "single point" ground and gives you the proper place to install other protective devices, i.e. rotor cable protector, telephone line protector, etc.

I recommend that the ground plate be made from ³ 0.125" stainless steel the dimensions depends on how many protectors need to be mounted. I selected stainless steel as it eliminates the dissimilar metals concern and allows direct copper attachment.

If you do not want to mount the plate in the house wall then mount the plate ON the house perpendicular to the wall very near to the coax HAM shack entrance. Run the coaxes on one side of the plate, clear of the house entrance, then from the opposite side of the plate run the cables and internal station ground conductor into the house. Connect the ground plate to a ground pipe that is within three feet from the house. The closer the connection between the nearest ground pipe and the ground plate the better the conductivity - I would use 1" or three 5/8" copper tubing pieces between these two points and then reduce the copper tubing size to the other ground pipes!

The ground plate is for mounting bulkhead surge/lightning protectors. The best protector and the ONLY one that I recommend and use is the PolyPhaserÔ type! See Appendix A. This is your last and best protection item. The PolyPhaser blocks and redirects the surge energy into your ground system. This also means that you need enough of a ground system to dissipate the initial energy and the ringing energy. See diagrams.

Ground Pipe/Rod placement

(Note:  Click on any image to see a larger version -ed. )

One of the biggest issues facing you is HOW MANY ground pipes/rods should you install? This is hard to determine as it is based on soil conduction, how potent is the lightning strike, how much room do you have, and what can you afford. If you look at a commercial system they have multiple ground radials (seven or more) each 32 feet long and four ground rods on each radial. Some of the ground rods can be sunk as deep as 40 feet. Well this is NOT in my budget or in most HAMs!

Obviously, the more ground radials and ground rods the better. I try to run at least three ground rods in a non-tower HAM shack. One directly outside the HAM shack at the coax cable enterance point (the shack ground), and at least two more ground radials with ground rods at their ends seperated by at least eight feet from the shack ground.

The tower increases the potential of a lightning strike so in addition to the above scenario two or more rods should be placed just for the tower. One rod near the tower base and the other rod eight feet away. Use 1" or two 5/8" pieces of copper tubing between the first tower rod and the tower.

The goal of a grounding rod is to make contact with the water table. Falling short of that it is to dissipate as much energy as possible. By driving the ground rod directly down attempting to traverse as many soil layers as possible so energy can be dissipated into these various soil layers. Some soils conduct better than others - dry sand being the worst followed by hard clay. But a hard clay layer may have some amount of water riding on the clay seeking penetration points.

Placing the ground rod at a 45° angle can increase to overall length of the radial and allow some energy to be dissipated. Angled ground rods are often used in rocky soil.

Interior Ground connections

(Note:  Click on any image to see a larger version -ed. )

The interior ground conductor is just as important as the exterior ground system. I run 5/8" copper tubing from the ground plate along the mop-board behind the HAM station desk. Using old RG-8 or (better) RG-9913 coax cable I strip off the outside plastic coating and expose the braid. Measure from the mop-board conductor to the back of each piece of equipment to be grounded. Keep the braid ground strap as short as possible. Strip the braid from the inside coax conductor. Solder the braid to the mop-board conductor and on the opposite end either heavily tin the braid and place a hole in the tinned area or solder an eyelet lug. Connect the braid to the radios, antenna tuner, computer, etc. Most radio equipment comes with an extruding bolt, washers, and a wing-nut - if not find a good chassis screw to place the braid with washer beneath.

The goals is to have an effective ground connection with short ground straps and to keep a clean unobtrusive appearance to the HAM shack.

Special Editors NOTES:

a. Watch out using push-up masts. They may NOT have good inter-section conductivity. Additional ground strapping between sections may be required.

b. Use conductive grease / moisture prohibiter under all exterior ground connections. Eliminate poor conductivity before it happens.

c. Use stainless steal clamps, bolts, washers, and nuts on all exterior ground connections, especially where making contact with copper.

d. The frequency of typical lightning is between DC to 1 MHz.

e. I did not cover grounding guy wires due to the fact that most installations use one or more insulators on each guy wire to keep the wires from becoming parasitic conductors causing RFI concerns. Or many HAMs use the guy wires (with judicious insulator placement) for make shift inverted "V" antennas. So grounding of the guy wires defeats the ancillary intent/antenna use.

f. Any conductor that could carry lightning should not make any bends smaller than an eight inch radius - the larger the radius the better. This requirement holds special significance to the connections between the tower, mast or ground plate!

g. Additional reference material sources:

Military HDBK-419 title

GROUNDING-BONDING and SHIELDING FOR ELECTRONIC

EQUIPMENT and FACILITIES

Military STD-461A title

REQUIREMENTS for the CONTROL of ELECTROMAGNETIC

INTERFERENCE and SUSCEPTIBILITY

PolyPhaserÔ GLEP title

The "GROUNDS" for LIGHTNING and EMP PROTECTION

Appendix A

Recommended equipment sources:

ACE™ Hardware (observed prices)

Copper pipe 0.5" x 10' $4.79

Brass Hose repair couplings $1.29 - 2.29

Brass Hose nozzle $1.69

Plumbers Flux $2.49

Copper soft tubing

1" $3.69 / ft. **

0.75" (3/4) $2.19 / ft. **

0.625" (5/8) $1.09 / ft.

0.5" (1/2) $0.69 / ft.

0.25" (1/4) $0.39 / ft.

Radio Shack™ (catalog prices)

Ground rod 8' $16.99

Ground rod 4' $ 8.99 BAD

Aluminum ground wire 40' 8 gauge $ 3.99 BAD

AES™ (catalog prices) 800-558-0411

Surge-Protectors

PolyPhaser™ IS-B50LU-C0/1/2 $59.95 BEST

Alpha Delta™ "T" type $22.95 # fair

Cushcraft™ LAC1/2 $13.00 # marginal

Tower/Mast clamp kit - eliminates dissimilar metal concerns

PolyPhaser™ 800-325-7170

TK-1-(.625-1.25") $ 3.95 GOOD

TK-2 (1.25-2.25") $ 3.95 GOOD

Copper cleaning kit - PolyPhaser™

CCK $25.95 fair

PolyPhaser™ 800-325-7170

Copper joint-compound (grease)

4 oz. FG 60500027 $15.00 GOOD

No Al-Ox - aluminum anti-oxidizer

good for antennas

FG 60500016 $15.00 GOOD

NOTES:

# = ONLY use for coax/hard-line to tower/mast base connection

** = special order - 60' coil minimum purchase

Member Comments:
This article has expired. No more comments may be added.
 
From the GROUND up  
by N6JSX on December 21, 2000 Mail this to a friend!
An additional note: From lessons learned when installing my ground system. Soldering a brass hose fitting directly to the top of the 10' copper pipe doesn't work. At the start of the drilling process the pipe is 9' above you and the hose kinks badly killing the water flow. Also the brass hose fitting can be tricky to solder. Oh the only place I found brass hose fittings anymore is at the old faithful ACE/True Value Hardware.

So I built a cheater fixture. I used two pieces of 12" copper pipe, 90 degree elbow, and a copper sleeve. I made an "L" shapped pipe assembly with the hose fitting soldered to one end and the copper sleeve to the other. Use a 1" 1/4-20 bolt and drill a hole through the pipe and sleeve - slip the bolt in the hole and mildly tighten the nut. Try not to overdrill the hole or you will get a shower! Solder the copper sleeve to the 10" copper ground pipe to be hydra-drilled. The hose will be horizontal and no kinking. When the 10' pipe comes down you can use the one side of the "L" as a handle to help drill/twist through graval layers!

When I started the hydra-drilling process I used a large ViceGrips to help me twist the pipe and move it up and down until the "L" fitting got with in reach.

Once the pipe is drilled to where you want it attach your flattened copper tubing. As you solder the tubing to the pipe you can pull the sleeve and fitting off - to be re-used on your next ground pipe. (This is where that bolt comes in handy - as the sleeve may become very HOT but it won't slip off the fixture.)

73, Happy Holidays!
Kuby, N6JSX /9 soon to be /8!
 
From the GROUND up  
by W2EJG on December 21, 2000 Mail this to a friend!

For the in-shack bus, I use copper pipe hanger strip. This is available at (old-fashioned) plumbing supply
houses. It has a series of holes drilled at regular intervals to permit attachment of many pieces of equipment. Most hamfests have lengths of braid strapping with "O" connectors already attached.
 
From the GROUND up  
by N6VQQ on December 22, 2000 Mail this to a friend!
This has been an excellent (for me anyway) lesson on grounding procedures, and I want to thank Dave for sharing this data.
As an addition to his posting, I would like to add something; I worked as a therapist in the biggest Burn Center in Southern California, and have seen many electrical burns, from various sources, and I know how hard it is to recover from this type of injury.
So for the sake of yourself, family and friends, take the advise you have read and apply it.
Happy and safe holidays to you all.

Ron N6VQQ
 
From the GROUND up  
by N6VQQ on December 22, 2000 Mail this to a friend!
I meant "Thanks Dale:
 
From the GROUND up  
by KF7CG on December 22, 2000 Mail this to a friend!
Good article! Your grounding set up seems similar to mine. I am lucky, I have a water table ground. This was not as easy to prepare as it was years ago. I have a separate heavy grounding lead from my central ground to the 5.5 galvanized well casing for my household well. Cold water pipe won't work as the pipe from the well to the house is polyethylene or a relative.

Electrical code for our area requires that the house plumbing be bonded to the electrical service ground. To eleminate some RFI problems, I have provided an external ground connnection around the water heater and the water softener/filters. Water heaters do not provide a continuous conductive path and neather do softener/filter systems.
 
From the GROUND up  
by KA4KOE on December 22, 2000 Mail this to a friend!
Has anyone mentioned potential difference in grounding systems. Shouldn't one bond your shack ground rod and electric service entrance ground together to prevent a voltage potential between your RF and AC grounds???

Thanks

Philip
 
From the GROUND up  
by N6JSX on December 22, 2000 Mail this to a friend!
Another additional note: The ground plate issue - instead of cutting a hole in the house - use a basement window (if you have one). Replace a pain of glass with this plate. Make it weather tight and all you lost was a little bit of sun light but look at what you've gained!

The advantage to this type of mounting is that you can "label" all your coax connections at the plate and disconnect coax's from the shack without moving your HAM gear everytime a storm comes or you go on holiday. You could even make PL-259/"N" connector direct short to ground plugs to connect inplace of the shack coax to further keep the lightening out!

If you put the plate in your basement workshop area you could use jumpers to the bench for more radio fun.

Don't forget to install some type of isolation protection device on your rotor cable!

Due to the cost of PolyPhasers it makes you plan your antenna system. To help reduce the cost I installed an Ameritron coax switcher on the tower for HF - only one coax coming down and five antennas to select from. Weigh that agains five PolyPhasers and the coax and you can see why!

I'm working on a tower mounted dual coax switch that is controled by voltage on the coax that can be used on VHF/UHF so I can switch beteeen a connected omni "J" or beam antennas or I could switch between horz. & vert polorizations on a cross yagi beam.
(surprised that a VHF/UHF remote dual antenna switch coax control with a COR RX pre-amp is not on the market - sure it would sell)

Just some more ideas - 73,
Kuby, N6JSX
 
From the GROUND up  
by KC4IWO on December 22, 2000 Mail this to a friend!
I live in a rented 1st floor apartment. I am lucky to be able to mount my HF6V, painted black of course, on a metal fence. I do use a 1:1 balun with lighting protection to iosolate the coax from the ant. I even use two 4:1 baluns and about 5ft of twin lead to get into the house. I have to use the twinlead so I can close the window down on it. I get good SWR and good signal reports. Since I am forced to such a tight setup there is no way I can set up a ground like this. I do use a homebrew tuner and counterpoise wire and tune up for the least amount of rf in the shack. I know I do not get the lighting protection, but it does seem to work very well.
 
From the GROUND up  
by K1ZF on December 23, 2000 Mail this to a friend!
Bravo!!!

Somone who understands RF. Good article; hope to see more like this on E-Ham.
 
Stainless Steel  
Anonymous post on December 23, 2000 Mail this to a friend!
The correct spelling is steel, not 'steal'.
 
From the GROUND up  
by K5MAR on December 23, 2000 Mail this to a friend!
Great article! As I'm putting up a small (40') tower this spring, this gives me lots of help in my pre-construction planning. One thing I haven't seen addressed in any articles on grounding is what to do if your shack location can't be next to an outside wall. My tower will be next to the garage wall, and my shack space will be in the house against the interior wall between the house and garage. Grounding the tower and coax won't be a problem, but the grounding for the shack is another story. I've even considered having a contractor cut a hole in the slab in the garage so I can run a ground cable through the wall. A second article dealing with this type of problem would be helpful for many hams, I'm sure.
Mark
 
From the GROUND up  
by WA4CNG on December 24, 2000 Mail this to a friend!
Very good article. In the commercial world (Land Mobile ESMR) our specification is 5 Ohms or less. The one thing I have learned from installing, testing, and measuring after the fact (semi-annual PM's) is that you are protected as long as everything that is connected to the single point ground stays at the same potential (ground resistance to the common point). When a Lightning Stroke occurs, if everything that is connected to the ground rises and falls at the same potential, you have no damage. The biggest risk is having two potentials in the same area and having a stroke occur. Small differences in ground resistance times the stroke current equals lots of potential voltages that will arc and spark till you see it and smell it. I have used commercial equipment to verify that my grounds meet that specification. My risk is a little less with In-Attic Antennas, but the stroke potential is still there.
 
RE: From the GROUND up  
Anonymous post on December 24, 2000 Mail this to a friend!
Great article! My ground system uses nine 8' foot rods fanning out from the tower and connected to a single-point copper bulkhead at the shack entrance with three additional 8' rods dropped at that point. I'm using I.C.E. lightning protection devices for coax and rotor cable, all mounted to the bulkhead. The interior shack ground uses Polyphaser's 1 1/2" copper strap back out to the bulkhead.

The ground potential question is still one that concerns me. My electrical service entrance ground rod is on the far side of the house. Going all the way around the house, pool and porch would require 120' of wire to connect it to the bulkhead. The straight line distance from the bulkhead to the service ground rod is about 60 feet. Is this distance sufficient (to avoid damaging voltage potential) or do I still need to run 120' of wire from the service ground rod back to the radio bulkhead?

73
 
From the GROUND up  
by K9GLN on December 25, 2000 Mail this to a friend!
Great article but I don't understand one issue. Why wouldn't you put the polyphasers at the bottom of the tower rather than at the ham shack coax entrance? I would think there was less potential to get the lightning charge into the shack that way as it would likely be dissipated at the tower base and not at the house. I have seen several tower set ups with the polyphasers mounted to a grounded plate at the base of the tower. Since I am planning to "go up" this summer I want to do it right. My tower will be about 40 feet from the house.
 
From the GROUND up  
by KD7EDW on December 27, 2000 Mail this to a friend!
Excellent article, however I must disagree with the practice of soldering grounding connections for the lighting protection side. Due to the extreme temperatures involved with current transfers of a lightning strike, a soldered connection can literally melt away before the strike is fully dissipated. The only approved method of bonding a ground rod to a conductor is by welding them together. Although this may seem inconvenient, there is a product called CadWeld that simplify this task. Ask your local electrical supply house for info on this product.
Installing lighting protection on you house may be regulated by local and state electrical codes, so you may want seek the advice of a qualified local electrician before starting.
Also a good rule of thumb for spacing ground rods is 2 ½ times their depth; that is, for 8-foot ground rods the spacing distance between them should be 20 ft. This gives you the maximum grounding effect.
 
RE: From the GROUND up  
by K0FUZ on December 30, 2000 Mail this to a friend!
If you want to read more about exeothermic welding and see some of those products go to:

http://www-public.tnb.com/utility/pages/ground_prodcat.htm

Also, when you buy your ground rods, I suggest you buy them at a electrical supply house. You want to ask for UL rods that will insure you get 10 mils of copper plating on the rods. If you want 13 mil rods, ask for the REA (Rural Elecrice Association) spec. of 13 mils. A good generic catalog number for the 8 foot 10 mil rod 5/8 inch diameter is 6258. If you want the same thing in 13 mil ask for a 6258-13MX. You want a U.S. made rod or you could wind up with junk. Look for the UL stamp on the rod if you get the 10 mil rod.
 
From the GROUND up  
by KD6OD on January 7, 2001 Mail this to a friend!
I too want to congratulate you on an exceptional article on grounding; I saw that one of the other guys went to a lot of trouble on his hydrological experience with copper pipe. I guess that the way I devised 20 years ago is pretty simple, but here goes... I use good old 3/4" copper pipe from Home Depot and I have two options: I have a brass hose fitting thats threaded which means I have thread one end of the pipe, or I have a brass fitting which fits on the pipe with a compression fitting, now you can get those in schedule 40 pvc too. My secret is that I get the extra elevation neccessary to drill the pipe into the ground by using a large STEP LADDER, I know thats not as high tech as the method that one of the guys went to, but I think for the average guy who's in a hurry to get the station airborne its a helluva lot simpler. I go down until I can get off of the ladder to finish the job and then leave about 6" exposed outside the wall in the flower bed, and then drill a hole through the wall to accept the 6 gauge stranded copper wire that attaches to my grounding bus mounted on a home brew 4 shelf equipment rack I built 20 years ago, and that leads to all of the equipment with 3/4 " wide silver tinned braid (the source of which and several other sizes were ham swaps where the price was right). That might be over simplification for some of you folks, but it works for me; I only have a push up for my 40 and 75 meter inverted v's at 42' and with the rarity of lightning here (I'm 13 miles north of Huntington Beach) I haven't worried too much about it since I made this intallation in Oct. 87, but you guys have got me curious about the impedance; tommorrow I'm going to check and see what it actually is. And now that I think about it if anyone knows a good cure for shielding your computer from an apparent overload of fundamental stray rf I'd sure like to know what it is; I just got this computer last Nov. and I haven't been able to spend much time on it due to overtime work demands of about 32 hours ot a week, but I'd sure like to be able to work 75 meters in the evening with the computer on........I've tried it and apparently my main processor becomes deluged with rf because the screen looks like something is tearing it apart when I pick up the mike and transmit voice. 73's Ron
kd6od@netzero.net
 
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