Service Opportunity: Christmas Village – December 19th, 20th and 21st

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The organizers of the Christmas Village – http://www.somdchristmas.com/ –
has asked for our assistance with communications during their event.

Where: St. Mary’s County Fairground. (though they promise to transform it
into a Charles Dickens-like avenue of lights and festive decorations. They
have over 100 vendors coming out along with carolers and live venue stage
events (school choruses and bands). This really promises to be something
special.

Dates: Dec 19, 20, 21 (see web-site for hours)

What they’d like us to help with? They have some limited commercial UHF
capabilities but could use some extra eyes and ears. Walk around the area
and enjoy the evenings with an eye on the people and an ear on your radio.

We’ll have a net-control radio located in conjunction with their
communications/operations area and will be sharing information anyone
needing assistance, lost children, etc.

What you’ll need:

* A 2-meter HT (we’ll be using 146.535 Simplex – low power should be
sufficient)

* A brightly colored safety vest (for example:
http://tinyurl.com/ldvu4ov )

* Warm clothes and comfortable shoes

* Flashlight

* A desire to serve your community

Tom Shelton would like 15-20 volunteers to spread out over the 3 days (do one, two, or all three – it’s up to you). Even if you can only give a couple of hours, your time would be greatly appreciated.

Please send an email to Tom Shelton at gl1800winger@verizon.net if you are able to assist.

Any question? Send Tom Shelton (gl1800winger@verizon.net ) an e-mail and He’ll answer them or find the answers for you. Tom Shelton will be the POC between the club and the organizers (Southpoint Church).

Annual Christmas Party (December 6th-2pm-Church of the Ascension)

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Our annual Christmas Party is coming up quickly. This year we are holding our Christmas Party at the

Church of the Ascension located at
21641 Great Mills Road,
Lexington Park, MD 20653.

Party starts December 6th at 2pm. The Executive Committee will be providing a turkey and a ham and are asking the club members to provide their favorite side dish.

The Church works on a donation basis so please bring some cash to toss into the donation box to help say thank you for letting us use their facility.

If you have any questions please forward them to Dan Metcalf via email at kb3uun@gmail.com. Hope to see you there.

Sign-up for the SMCARA email reflector

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To sign up for the St. Mary’s County Amateur Radio Association’s email reflector got to http://mailman.qth.net/mailman/listinfo/smcara

Under the area “Subscribing to SMCARA” enter the following:
Email Address, Name (optional),  Password (so you can come back and change you options),  Confirm your password and Lastly answer the question “Would you like to receive list mail batched in a daily digest? Yes / No

Once you have filled out the form click “Subscribe” and your request will be sent to our administrator for approval.

Once approved you will be able to send messages to smcara@mailman.qth.net and it will be reflected to the other subscribers. Just remember pictures and attachments will not be forwarded.

Local Frequencies (St. Mary’s County)

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Saint Mary’s county area repeaters:
Two meters:
146.640 MHz Negative Offset PL 146.2 (Located in Lexington Park, MD)
145.350 MHz Negative Offset PL 156.7 (Located in Prince Frederick, MD.  Wide area coverage)
147.420 MHz SIMPLEX Echolink. PL 156.7 (Located in Leonardtown)
146.600 MHz SIMPLEX D-Star Hotspot. (Located in Lexington Park)
147.195 MHz Positive Offset D-Star (Located in Hollywood, behind the VFD.)

70 Centimeters:
443.050 MHz Positive Offset (Located in Lexington Park)

The list I have is from 2009 so if there are any others please send me an email at kb3uun@gmail.com with the updated information.

Lightening (SIC) by Ray W3JIW – Complete.

LIGHTENING(SIC) FREQUENCY
   Photometric observations from the orbiting solar observatory Satellite OSO-2 showed ten times as many lightning storms occurred over land as over the ocean. It was learned that the North Atlantic Ocean has more lightning storms than similar areas of other oceans. Few lightning storms occur over desert regions, according to satellite findings. One of the most active lightning regions in the world is Java and in the United States-Central Florida holds that distinction.  There is a popular misconception that lightning never strikes twice in the same place when in fact it frequently does. The Empire State Building in New York City is a good example of repetitive strikes having been struck as many as 48 time in one year.  The assumption that the pulse
rises to maximum value in 1.2 micro-seconds and in  50 micro-seconds the impulse will have fallen to 50% of the crew or maximum voltage.  The flash we see is actually a return stroke from earth to cloud at a speed of 100 million feet per second or about 100,000 times as fast as sound, completed in one ten-thousandth of a second.

The eye cannot distinguish it other than a downward stroke.  Space Technology with high speed camera have allowed us a better look at the step leader or pilot streamer.  A bolt can have a potential as high as 15,000,000 volts and deliver an average of 5,000 to 20,000 amperes to its path.  At Cape Kennedy a recorded peak of 100,000 amperes on a strike to a launch tower in 1971. It is no wonder, then, that its explosive force can demolish a tree or otherwise severely damage property.  The Tree explodes when the water and other substances in it are vaporized.
                                TABLE I
                   Significant Lightning Characteristics
            Charge Range            2 to 200 Coulombs
            Peak Currents           2 to 400 kiloamperes
            Discharge Duration      1 to milliseconds
            Rise Time (to 90%)      1 to 10 microseconds
            Relaxation Time         40 seconds to many minutes
            Field Strength          3 to 5 kilovolts/cm
            Cloud earth Potential   108 Volts

TOWER GROUNDING CONDUCTOR
   A common practice is to use copper wire attached to a galvanized Tower leg or guy wire anchor.  Also joining a pure copper grounding conductor to the zinc-covered steel will produce an unwanted electrolysis action which in fact washes away the zinc coating.  So the ensuing corrosion will shortly result in a poor connection or even an open circuit.  Painting or coating will stop such an action.  ONLY IF ALL MOISTURE AND AIR are depleted under the coating.
You can use a buffer metal such as bronze, stainless steel, or brass.  Or better yet use an exothermic welding process.  A widely used method is known as CADWELD (r) this is the TM of Erico Products Inc., 34600 Solon Road, Cleveland, OH, phone (216) 248-0100.  The molds to use in the application are Graphite and reusable for many connections.  However these molds are not cheap currently they probable exceed $50.00.  This process provides de-oxidized molten copper which mixes with the upper zinc coating or steel to form an air tight connection of the conductor to the other metal part.  Some favor the addition of a copper down conductor running down the length of the tower. The idea recognizes that resistance between tower sections averages about
.01 ohm. Thus a bolt could cause a large voltage drop.  This is largely overridden by the inductive voltage drop which far exceeds the resistance drop.   Also the tower inductance is much smaller than any copper conductor.

The tower has a much larger conductive surface and is not subject to the large inductive effect due to skin effect on the small conductor.  From this the copper conductor effect is really nil.  Another detrimental factor is the potential electrolytic effect.  If the copper contacts the tower and you have moisture it cause the galvanizing to wash off.  Another excuse for using such a conductor is to minimize NOISE and EMI (Electromagnetic Impulse)/RFI (Radio Frequency Interference) problems.  When lightning strikes a tower, it has
little or no effect on a normal joint.  If a tower has been up for many years many joints have become oxidized.  If winds have not moved the tower enough to clean bolted connections or if the joints are loose, noise can result. Regular small discharges of lightning to a tower can increase the resistance.  A tower down conductor is a quick fix??  It may eliminate some of the noise but It doesn’t cure mechanical problems.  And it will not prevent joint arcing during a strike.  A real fix is to have tower crew loosen every bolt slightly and re-tighten.  Afterwards paint or seal all bolts, nuts, and joints. Make sure not water will be encapsulated by the sealant.  I used to use a Propane Torch drive the moisture out prior to sealing.

TOWER GROUND CONNECTION LOCATION
   Bends with a radius of less than 8″ increases the inductance of any conductor.  My personal preference is a minimum radius of 12″.  The important idea is that right angle bends and short radii can cause problems.  However the some trade offs can be even worse.  Let us suppose that we had a tapered base tower and the ground rod is 24 inches from the concrete base pad.
   Your choices are:
      (1) Run the interconnection through the air from the ground rod to the plate which is full tower area.  This should have the minimum amount of bending and be almost vertical.
      (2) Connect the ground rod to a second plate – a compromise.
      (3) Make a connection directly from the ground rod to the first plate.  This path places the interconnection through the least amount of air, but has the most bends for the surge current.  If you are using #2/0 wire its inductance is 0.32 micro Henry/ft.  Knowing the lengths, the inductance for each choice may be calculated.  Each 90 degree bend adds about 0.2 micro Henry of inductance.  Each sharp angle has about 0.57 micro Henry Inductance.

When we speak of Lightning Protection actual two general conditions exist:
   1) We are speaking about a structure which may or may not be associated with some electrical equipment.  In a more narrow look it could be a home located in a lightning prone area.  For example we it might be a mountain top or a desert region.  Fortunately desert regions are not usually prone to much lightning.  But when a bolt strikes it is just as devastating.  However, installing a suitable ground system is a problem.  Here we usually have low conductivity (usually sandy) soil and low moisture content.  There is a grounding system called the “UFER” which uses the reinforcement steel for a ground conductor.  More will be given elsewhere in the text.  And on a mountain top surprisingly enough you find a very thin layer of soil and many boulders giving a high resistance condition.
   2) We may also be referring to a tower or towers associated with a structure housing communications equipment.  The location problems referred to in item (1) are also applicable for these installations. It is very important that we understand the latest information on protection of Tower mounted equipment such as Antennas, Weather  measuring instruments.

CONDUCTORS AND ROUTING
   When we speak of conductors it is important to remember to use ONLY SOLID Conductor!!  I have referred to #2/0 as a size often used.  This is useful in many areas.  However there is another very useful conductor, copper strap.  Even though strap as thin as 1/64 inch it is still useful. A thicker strap is only useful to ease the problem of connection.  Here we must find out about “Skin Effect”.  The current only penetrates to a depth of a few thousandths of an inch in any conductor due to “skin effect”.  Here the inductance of the conductors rears it ugly head.  The routing of any of the conductors becomes important.  You must also remember the braid of the coax line is a conductor. Always run the coax down inside of the tower.  Of course it must be suitably mechanically supported.  If you run any other conductor down the tower KEEP IT INSIDE the tower.  Now you ask why.  If they are placed outside the tower you now have the inductance of the tower and the conductor in parallel.  When the magnetic fields are separated the individual conductors now have an increased inductance.  This might not be all bad as it limits the current to earth.  However the current may take a different path also.  BE ABSOLUTELY  SURE THAT NO CONDUCTOR FOR LIGHTNING PROTECTION PASSES THROUGH A SHORTED TURN.

Let’s talk about shorted turns.  If a conductor is fed through any length of Metal Conduit or Pipe that is a shorted turn!!  Even a hole cutout for a conduit in a Metal Box is a shorted turn!  Now back to conductors.  The use of straps for connecting ground rods are very useful.  An  old rule of thumb for the width of copper strap that is 1% of the length of conductor you are going to use. For example a 20′ length should have a width of 2.4″.  It must be remembered that you will have to use a thicker strap on both sides of the conductor for strength where you are attaching ground rods to the equipment.

GROUND SYSTEMS:
   I must assume you have some control of the Ground System associated with the tower in question.  Unfortunately most repeaters are placed on Existing towers through the generosity of its owner.  It was probably installed by a contractor.  Usually they were not given a detailed plan of installation!!  All grounding depends on the earth involved.  Any ground system must be considered as a large ball of earth.  It is used to dissipate the energy from a bolt of lightning by converting it to heat in the bulk resistance. This is a measurable value called “Bulk Resistance”.  Where we are referring the Ohmic resistance of a centimeter cube.  Remember we are dealing with a cube of soil that has a one centimeter dimension on all sides.  We also suppose the soil
somewhat uniform in its average resistance.  The only possible improvement in a Ground System is to enlarge the so called ball.  This also has its limits. We can improve a system by using an interconnected array of Ground Rods around the base of the tower.  It is very important that the conductors for the multiple Ground Rods be of low inductance and resistance.  Here a suitable copper strap is the best.

I am not including details on the arrangement of grounds.  Ground rods  Come in many sizes and lengths.  The more common ones are 1/2, and 5/8 inches in diameter.  They comes in steel with galvanized, stainless, or copper clads.  A common length is eight feet.  At your home station.  The top end of a ground rod should be below the surface of the earth to about the frost line limit.  You can improve the situation by using one of the foam type insulations.  Then use a piece of outdoor plywood to cover the fragile foam insulation.  Why would this be necessary?  If the rod is a good conduction of heat it is also a good conductor of cold.  The ground rod you thought was so good, could have a sheath of ice along its length.  The resistance of ice is about 30,000 ohms/cm
cube.  Yes ice formation drives the minerals in the water to the zone that was the last to freeze.  Therefore you have a high resistance ground.

Some may question the need because lightning is no problem in the winter. You better think again.  Many fellows find unusual RF Feedback Problems in winter. I must repeat the importance of copper strap with the lowered inductance. The steepness of the wave front from a bolt of lightning is the same as a high frequency alternating current (RF) in its behavior.  This behavior results in most of the current flowing on the surface of the conductor.  The common wire conductor is #2 AWG (American Wire Gauge) stranded copper.  However #2 solid copper is much preferred.  If you are using #2 solid copper it is equivalent to a strap 13/16″ wide.  This means the effective resistance is of less than one seventh of a copper strap.  It is important to remember that if you are connecting a ground rod to a metal strap it is necessary to reinforce that point.  Use lengths of heavy copper strap on each side of the strap then clamp
in position.  Of course Brazing or Silver Solder is preferred to a mechanical connection or clamp.  Most clamps are as useful as a Politicians Promise.

SOME TABLES OF INTEREST
        TABLES APPLYING TO GROUND RODS AND SOIL RESISTIVITY.
         *** TABLE I ***                    *** TABLE II ***
     EFFECT OF MOISTURE on                EFFECT OF SALT CONTENT on
        EARTH RESISTIVITY                      EARTH RESISTIVITY
MOISTURE       Resistivity OHM-CM         * Sandy Loam 15% Moisture
 % by Weight  Top Soil Sandy Loam      % Salt by Weight   Resistivity
  1.0      1,000x106  1,000x106          0.0              10,700
  2.5    250,000      150,000            0.1               1,800
  5      165,000       43,000            1.0                 460
 10       53,000       18,500            5.0                 190
 15       31,000       10,500           10.0                 130
 20       12,000        6,300           15.0                 100
 30        6,400        4,200

        TABLES APPLYING TO GROUND RODS AND SOIL RESISTIVITY.
        *** TABLE III ***                     *** TABLE IV ***
       RESISTIVITY OF SOILS                TEMP. EFFECT RESISTIVITY
 SOIL       RESISTIVITY OHM-CM-CUBE       * Sandy Loam 15% Moisture
                         (Range)         TEMPERATURE     RESISTIVITY
Surface Loam, etc    100 –     5,000       C       F    Ohms CM-CUBE
Clay                 200 –    10,000      20     68             7,200
Sand & Gravel      5,000 –   100,000      10     50             9,900
Surface Limestone 10,000 – 1,000,000       0     32   (Water)  13,800
Limestones           500 –   400,000       0     32    (Ice)   30,000
Shales               500 –    10,000     – 5     23            79,000
Sandstone          2,000 –   200,000     -15     14           330,000
Granites, Basalts       100,000
Decomp. Gneisses   5,000 –    50,000
Slates, etc.       1,000 –    10,000

        TABLES APPLYING TO GROUND RODS AND SOIL RESISTIVITY.
       *** TABLE V ***                         *** TABLE VI ***
    EFFECT OF ROD DIMENSIONS             NUMBER & SPACING OF RODS
 MEASURED OHMS  ROD DEPTH FEET         No. of    Spacing  Reduction
   160                .9                Rods      Feet     ‘R’ %
   140               1.0                           5′     10′     20′
   120               1.3                 2        60%     55%     50%
   100               1.8                 3        48%     42%     37%
    80               2.4                 4        42%     35%     30%
    60               3.3                 5        38%     30%     26%
    40               5.0                 6        36%     27%     25%
    20              12.0

PLACEMENT OF ANTENNA
   Now for the antenna location the tower.  Never put the antenna on the TOP MOST PART of a tower!  If you do it is just a Lightning Rod!.  You must electrically shelter the antenna.  This is done by placing an array of rods 1/4 wavelength above the tip of the antenna so the pattern and radiation will be least affected!  This will be several rods in a spray pattern.  It is assumed that the antenna will be 1/4 Wavelength from the tower.  Then if the rods exceed 1/2 wavelength in length for the lower frequency in use.  We will achieve the desired effect.  The ends of the rods must not be pointed.  The ends of the rods must be looped around like an Eye Bolt.  A similar arrangement must be place 1/4 wavelength below the antenna.  All to minimize interfering with the antennas radiation and reception.  If you are using a single antenna the tower should be so it is between the antenna and the direction that a slight loss of coverage is the least problem.

When an antenna is spaced 1/4 Wavelength away from a small tower there Is usually no problem.  However towers with a large cross section may Require a multiple antenna insulation.  However some communication with the antenna manufacturer may be needed.  Believe it or not a “J” Pole with the radiation part pointed down and its supports grounded to the tower is good.  Such an installation with the antenna pointed often eliminates some icing problems.

Now you are asking why does this system work?  I had been found that lightning can be expected to act as if had a radius.  The placement of the rods above and below the antenna gives the lightning somewhere to land instead of the antenna!.  Of course you cannot neglect using a strap to properly ground the shield of the coax!!  Likewise the tower must have low inductance.  This as any other system is not fool proof.  But it can reduce the probability.  I have said little about the arrangement of ground rods.  If I figure a reasonable way to show it as above I will send it later.

Lightning Primer by Glen E. Zook, K9STH

Since I have been asked to provide to the subscribers of the Glowbugs reflector a treatise on lightning including grounding techniques, prevention techniques, as well as theory, I am submitting the information in a series of postings.  There are several reasons for this including the length of the manuscript and the time it takes to prepare the information.  In addition, the size of an E-Mail is definitely limited by the reflector.

There are definitely numerous opinions on the subject of lightning as well as on the related, but completely separate, subject of r.f. grounding.  I am not implying that the ideas expressed by me are the only way of doing things.  However, they have proven their worth over a number of years of implementation in the field.

First of all let me set forth my credentials:  I have been a licensed amateur radio operator for over 42 years and have held a commercial radiotelephone operator’s license for over 39 years.  My college degree is from the Georgia Institute of Technology, better known as “Georgia Tech”.  In addition, I hold certification from the Personal Communications Industry Association in the two-way radio field.  Also, I have certification as a Registered Communications Distribution Designer that is administered by the Building Industry Consulting Service International.  This is “akin” to, but definitely not the same as, a Professional Engineer but specializes in the communications industry and is recognized on an International scale, not just statewide as the PE.  I have been officially employed in the telecommunications industry since 1965 when I was a junior in college.

For over ten years I was employed at Texas Utilities (now “TXU”) with primary responsibilities for their two-way and microwave radio systems.  In addition, for the last five years of employment I also handled inspections, etc., of the infrastructure data wiring, etc.  In May of 1999, TXU basically eliminated the telecommunications department and since then I have been doing consulting, writing, and even repair of “boat anchor” amateur equipment for others.  I have been presenting talks and seminars on lightning protection and r.f. grounding for a number of years to various organizations including amateur radio groups.  My presentation was video recorded this past summer and is now available (or so I am told) to colleges and universities for use in their education processes.

Now, to get started on the subject of lightning:

First of all, each and everyone have been “hit” by lightning at some time in their life.  In fact, many people are “struck” at least several times a month, if not daily!  Impossible you say!  No, just walking across a carpeted floor or sliding across the seat of an automobile produces “static electricity”.  When you reach for a “grounded” object, a small “spark” is drawn from you to that object.  That is nothing more than a lightning strike!

A simplification of the mechanics of a lightning strike consists of a charged mass (usually, but not always a cloud bank) that moves into an area.  Since nature likes to remain in balance, the presence of this charged mass causes an opposite polarity charge to start to be drawn from the Earth.  When the potential of the differences between these two oppositely charged masses reaches certain intensity, the equalization of potential (the reduction to zero voltage) takes place.  This equalization is better known as a lightning strike.

When anything is erected above the surface of the Earth, it starts “attracting” energy from an area that is approximately a circle with a radius of twice the height of the item.  For example, if a vertical antenna is erected that has a height of 50 feet, it “attracts” energy from a circle with a radius of 100 feet (or diameter of 200 feet).  Now, the cross-sectional area of a tube with a diameter of 0.75 inches and a wall-thickness of 0.32 inches (this is a very common size used in vertical antennas) equates to an area of 0.075 square inches.  This is the total surface area from which the energy has to be dissipated.  The area from which the vertical is “drawing” energy is 31,416 (to the nearest square foot) or 4,523,899 square inches.  The ratio of the 0.075 square inch “radiating surface” to the area from which the energy is drawn is 60,318,647

If a charge equal to 1 volt per square inch is “acquired” from the surface of the Earth, this becomes over 60 million volts per square inch at the top of the antenna!  That is one “heck of a” potential to be equalized.

There are two definite theories in the area of lightning protection.  The first is to take whatever precautions are necessary to prevent a strike (and there are definitely some).  The second is to ground the “hell” out of everything to allow a strike to be taken without doing any damage.  My ideas are to take the precautions against taking a strike and then grounding everything “just in case”!  Frankly, there is nothing that will insure absolutely that you will never take a lightning strike.  However, there are relatively simple things that you can do to cut this possibility by 99.99 percent.

Contrary to popular belief, lightning does not start from the sky, but starts from the “ground up”.  The vast majority of the equalizing charge does come from the charged mass in the sky.  However, the strike actually starts from the ground in the form of a “feeler”.  If you can keep these “feelers” from starting, you will keep lightning from striking.  How to do this will be covered in the next installment.

If “feelers” do not start, there will not be any chance of a lightning strike.  Therefore, if at all possible, dissipation devices should be installed on the antenna structure.  Unfortunately, if the antenna is a single vertical, it is extremely difficult to install a dissipation device unless it is also used as a “top hat” loading device and the antenna itself must be grounded (shunt feed, etc.).  When a tower, mast, pole, etc., is used, then such devices can be installed with no effect on the antenna(s).

The purpose of a dissipation device is to dissipate the charge “acquired” by the antenna system before it reaches the potential where a “feeler” is formed.  This is accomplished by having a relatively large surface area at, or near, the top of the structure to “handle” the charge (“spline ball”).  Or, in the case of a dissipation brush, a large number of “points” available for this purpose.  As the charge is acquired, the dissipation device “bleeds” off the electricity into the atmosphere.  In some cases, during periods of extreme activity, the dissipation device may actually “glow” (corona forms).  This is fine!  When a corona is present, there is no chance of a “feeler” starting.

Dissipation devices need to be installed on each leg of a tower, not just one leg.  They need to go at the top, or within a foot or two of the top of the tower.  However, they do not have to go on the mast, etc., that comes out of the top of the tower.  If the tower is less than 100 feet in height, normally one set of dissipation devices will suffice.  At about 100 feet, two sets should be used, one set “half way up” and the other at the top.  With heights over 150 feet, dissipation devices should be installed every 75 feet starting from the ground level.

“Spline balls” are available from a number of commercial sources and cost from over $100 upwards.  These are normally constructed of stainless steel and consist of a large number of metal strips connected to a central point.  Dissipation brushes are also available commercially and can be easily constructed by the amateur radio operator for about $5 to $10 each.  In addition, some persons have been able to find steel brushes made for chimney sweep activities for about $15 each.  However, I have never been able to find these!

The construction of dissipation brushes is easy.  If the brushes are to be mounted at the top of the tower (sticking “straight up”), then a 12 inch long piece of ¾ in diameter galvanized electrical conduit (e.m.t.) is used.  Two “notches” 1 inch long are cut at right angles in one end.  Using galvanized electric fence wire (available in ¼ mile reels at home improvement centers for under $10) the brush is constructed.  Cut about 150 lengths of wire, 15 inches long, from the fence wire.  Put a hose clamp that fits the ¾ inch conduit around the notched end.  Then, with all the wires held together, insert the fence wires into the conduit.  Next, tighten the hose clamp.  Then, using acid core solder and a propane torch, solder the conduit and the wires together.

To attach the dissipation brush to the tower, use two metal hose clamps and tighten well.  Since the purpose of these devices is to “drain” the charge, the physical connection of the hose clamps between the tower (or mast) and the dissipation brush is sufficient.  If it is installed on a wooden pole, then a ground wire (12 gauge is normally sufficient) will have to be run.

For brushes to be used on the sides of the tower (or they can be used on top as well), take an 18 inch long piece of conduit and bend it about 45 degrees 6 inches from one end.  Then cut the notches at the other end.  Follow the instructions above for building the dissipation device.  Remember to make one device for each leg of the tower.

Installing these devices will help considerably in preventing a lightning strike.  However, there is nothing that will insure that you will NEVER take a strike.  But, by installing dissipation devices you will cut your probability of taking a strike by about 99.99 percent.

The next installment will cover proper grounding techniques for tower legs, etc., and for the grounding of coax before it enters the shack.

Direct grounding of the tower, mast, etc., is of prime importance for lightning protection.  Even if dissipation devices are installed, they are not 100 percent effective in eliminating the prospect of a lightning strike.  Therefore, additional precautions must be taken “just incase” you take a strike.

First of all, NEVER use a ground intended for r.f. for lightning protection (conversely, never use a lightning ground for r.f.).  The methods use for getting a good r.f. ground are different from those used to get a good ground for lightning protection.

Each tower leg MUST be grounded separate from the other legs.  This can be accomplished by driving solid copper-clad steel rods into the ground at least six inches outside of the concrete pad on which the tower is mounted (or is actually “in”) directly in-line with the tower leg.  Next, use #6, or heavier, copper wire for the ground wires.  It doesn’t really matter if the wire is insulated or not.  For this purpose, stranded is better than solid.  It is not the current carrying capability of the wire, but the fact that solid wire is more easily distorted which definitely affects the lightning protection ability.

It will depend on how far out the ground rods are from the tower legs as to how high they should be attached to the tower.  The further out the rods, the higher you have to go on the tower.  The “angle” between the ground wire and the tower should not be greater than 30 degrees, and the smaller the angle, the better it is.

Remove about two inches of insulation from each end of the wire if it is insulated.  Next, attach the wire directly to the tower leg using a good, heavy, type of clamp (these are available at home improvement centers).  Do NOT use the “hole” in the clamp that is provided for wires, but clamp the wire directly to the tower leg (the end of the wire that is clamped will be up).  Some people like to “CAD weld” these ground wires, but I do not like to do this.  Bring the wire downward in a very gentle “arc” to the ground rod.  Using a similar clamp as on the tower leg, clamp the ground wire directly to the ground rod.

What ever you do, do not have any arc in the ground wire with less than a 12-inch radius.  Never reverse direction of the ground wire even the slightest (lightning will not usually follow the wire if the radius is less than about 10 inches and will “jump” to “who-knows-where”).   Any “right” angle in your ground system will cause the lightning charge to go elsewhere.  This is one of the reasons that I do not like using CAD welds for the attachment of the ground wire to the tower (it puts a “right” angle in the system).  Also, especially on the smaller diameter tubing towers that are the most commonly used on amateur systems, CAD welding can greatly weaken the strength of the tower leg if not properly done.

Coax should be grounded at the top and bottom of the tower.  This includes Heliax, and any other type of shielded cable.  This can either be accomplished by purchasing grounding kits from Andrew, or other cable manufacturer, at a significant cost, or by making your own for less than 50 cents per connection.  I choose to make my own!

Remove about 1 inch of the outer sheath of the coax (baring the shield).  Next, take a length of braid (like has been removed from an old piece of RG8/U, etc.) about 6 inches to 12 inches long.  Using a small hose clamp, clamp this braid to the shield of the coax.  Then, use the very cheap black plastic tape (the 39 cents a roll stuff – do not use any 3-M product) to tape the connection very well to waterproof it.  In a week, or so, of exposure to the sun, this “cheap” tape “congeals” into a sticky, “gooey”, waterproof mass.  The “good” 3-M tape comes loose when exposed to the elements.  Decibel Products used to include a roll of this “cheap” tape with every one of their commercial antennas to waterproof the connections.  I have taken apart connections that were over 20 years old waterproofed with this type of tape.  They looked just like they had been made (no corrosion, etc.!).

When each of the coax cables has had a ground wire attached, then attach these to one of the tower legs using two hose clamps to hold them in place.  Do the same thing at the bottom of the tower.  If there is over 10 to 15 feet between the tower and the entry into the building, then another ground should be put on the shields of the coax cables.  This ground should be attached to some type of ground plate, or, they can all be connected together and brought through a single ground wire to another ground rod driven at the side of the building.

If properly done, there is no reason to disconnect your antennas whenever a thunderstorm comes into the area.  Frankly, my antennas have been up over 29 years and they are never disconnected.  I have had no damage at all.  My primary tower has a 3-element 20 meter monobander, a DB-1015 for 15 and 10, a 2-element homebrew yagi for 12 meters, a 3-element six meter, and stacked 11-element beams (2 each) vertically polarized for 2 meters.  My secondary tower has a 7-element 2 meter yagi, 11-element 222 MHz yagi, and 3-element 6 meter yagi installed.  None of these has ever taken a strike.

Remember that good grounds are not “pretty”.  You NEVER want a large angle bend.  You NEVER reverse the direction of the ground.
 Copyright 2002 by author

2nd Annual Southern Maryland Tailgate Fest (October 25th 2014)

Come out and join us as the St. Mary’s County Amateur Radio Association holds our second annual Southern Maryland Tailgate Fest.
Last year was such a success we decided to do it again.

Where: Bingo Hall behind the Hollywood Volunteer Fire House located at
24801 Three Notch Rd
Hollywood, MD 20636

When: October 25, 2013 6:30am Setup, Open to public 8am – 1pm

Admission is free. Tailgating / Table fee is $5.00 (all proceeds will go to fund next years event).

If you would like to tailgate and would like to reserve a spot please contact Dan Metcalf via email at kb3uun@gmail.com. We still have tables available in the Bingo Hall and we have plenty of room in the parking lot around the Bingo Hall.

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This event is an ARRL affiliated event and as such the ARRL had provided $100 dollars in gift certificates to be raffled off during the event.
Raffle tickets for the several raffles that will occur during the Tailgate Fest will go for $1 for 1 Ticket and $5 for 6 tickets. Good luck!

Public Service Event: Chaptico Classic (August 30th 2014)

The Chaptico Classic Event Planners have once again invited us to help out in providing communications for their event. In participating in this event we are there to help in ensuring the safety of the participants by calling in when help is needed. We also help in providing status of the race by tracking the first and last of the participants. All licensed Amateur Operators are invited to participate.

Based on past tradition the schedule will follow accordingly:
Breakfast: 6:30am McDonalds in Leonardtown, MD
Convoy to Site: 7:30am Chaptico, MD
Race Starts: 8am

Race in the past has ended by 11am to 11:30am. Please mark you calendars and plan to support this event. A good showing from the club will go a long ways in getting us more public event work. Wearing of the red club shirts is encouraged.

Please RSVP as soon as you know what your schedule is to kb3uun@gmail.com