Friday, November 29, 2013

Antenna Safety. Post #246

In the excitement of designing, building, and erecting my "homebrew" wire antennas, I've often neglected to consider important safety issues which could affect the location of my antenna and perhaps save my life.
A few years ago, I erected a vertical antenna which gave me excellent service until a lightning strike turned my work of art into a mess of shattered fiberglass, pvc pipe, wire fragments, charred coaxial cable, and a severely damaged ego.  Fortunately, I had disconnected the feed line from my shack and had it connected to a ground rod.

Ever since that lucky escape from Mother Nature, I've had a firm respect for the weather and "Murphy's Law" (whatever will go bad will fail at the most inconvenient time).

Over the course of my amateur radio "career", I've followed a few basic guidelines to erecting antennas, whether they be commercially bought or built from my own resources.

PLAN AHEAD

I know this sounds pretty basic, but thoroughly outlining your antenna project, assembling all of the parts beforehand, and doing a general survey of your property for hidden dangers can pay big dividends later.

Before I build an antenna, I walk over the area for the proposed antenna site.  I note any safety hazards such as uneven ground (especially dangerous when you have to disconnect your antenna at night), proximity to power, telephone, and cable lines, and visibility concerns (there's always someone who hates antennas and will tell the world about it).

After I'm done with my initial inspection, I ask someone else (my xyl or another ham) to look around for anything I might have missed.  Another set of eyes is always helpful in picking out questionable objects on the antenna field.

I also draw a rough diagram of the proposed antenna and its placement on the property.  This drawing is filed in my antenna notebook and will be used to make revisions to the design.

Once the basic plan is drawn and the property checked for suitability, I then advance to the second phase of the antenna project.

BASIC SAFETY ASSUMPTIONS

Assume that everything connected to the antenna structure is conductive.

Assume that the antenna or any part of it, including supporting masts, guy lines, feed lines, and antenna elements will fail or break at the most inconvenient moment.  Be sure your construction is sturdy and can stand up to the weather.

Antennas should be kept far away as possible from utility lines, both from the pole carrying the energized lines and the entrance of these wires into your home and shack.  At my current location in a crowded neighborhood, I've had to resort to small verticals and low slung dipoles and loops to maintain a safe distance from power lines.  At my new home in the Puna District, my nearest antenna structure (a 33-ft/10.06 meters fiberglass mast) is about 100 ft/30.48 meters from the nearest utility line or cable entrance.

If possible, lower your antennas to ground level after you are done operating.  This will present less of a target for lightning or snoopy neighbors.

Disconnect all antenna feed lines from your equipment when the operating day is over.  I use a window patch panel to run coaxial or ladder line feeders into the shack.  The external leads are connected to an 8 ft/2.43 meters ground rod at the base of the antenna mast.  A set of four, 33 ft/10.06 meters radials are connected to the ground rod and form a spoke pattern around the base of the antenna.

Be sober when you build and erect your antenna.  Alcohol and antenna building are a bad combination, especially if you are erecting a tower.

If you are uncertain about erecting a mast or tower, get help from your local amateur radio club.  Even if you are working alone on a simple vertical, be sure you have safety equipment for use, including gloves, hard hat, and good work boots.  If your project involves the use of a tower, be sure to get climbing belts and other tower climbing equipment.

If you are using a commercial antenna, be sure to follow all instructions and procedures exactly.

Be sure you have a written outline of how the antenna erection will  proceed. Give copies to your antenna crew if you have one.  Include in your plan the procedures you'll use to correct any failure of equipment or parts.  Before you erect your antenna, do a "dry run" of the antenna construction and raising.

If at all possible, build as much of the antenna on the ground as you can.

If you'll be using a mast to support your dipole, inverted v, or vertical, install a simple halyard-pulley system on the mast to raise or  lower the antenna should the need arise.  This system will come in handy for antenna adjustments or to lower the antenna during bad weather.

Avoid bad weather, especially storms with thunder and lightning.  Build and erect your antenna during a calm, sunny day if possible.  The antenna can wait.  Your life won't mean much if you're in the way of a lightning strike.

OTHER THOUGHTS

When I get through working DX or some laid back local contacts, I always do the following:

Disconnect antenna feed lines and connect them to the ground rod at the base of the antenna.

Unplug all station equipment.

Install a static discharge system on your antenna feed lines.  While this step won't protect you from a direct lightning strike, it will "bleed off" static electricity that builds up on antennas.  Some of the newer solid state transceivers are quite sensitive to electrical discharges.

There are probably many other steps you can take to insure a safe, efficient antenna system.  I've listed a few articles which explore antenna safety issues in depth.  These essays are worth reviewing.  Good luck in your next antenna project.

REFERENCES

http://www.arrl.lorg/files/Technology/tis/info/pdf/016091.pdf.
http://www.universal-radio.com/catalog/wideant/safewide.html.
http://www.hamuniverse.com/antennasafety.html.
http://www.cisco.com/en/US/docs/wireless/bridge/350/installation/guide/BR350apC.html.
http://www.k2zs.com/indoor-antenna-tips/constructiontips.

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Thanks for joining us today.

Aloha de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.