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Safeguards in roof-top installations.
Antennas improperly installed on apartment-house roofs in thickly-populated areas can constitute a severe hazard not only to property but to personal safety as well. Cliff-dwellers would do well to heed the suggestions made here by a "voice of experience."
Many of us amateurs who live in large apartment houses are confronted with certain situations and problems which our country brethren do not have. I live in a fifty-eight-family apartment, and the roof is a forest of TV antennas in all stages of neglect. Over one third are on the roof top, having come down at one time or another.
During the past eighteen years I have erected many antennas, and only one has stood the test of time. The masts have been up for over fifteen years, and they have withstood every storm and hurricane that came along. I have a graveyard of antennas which did not last more than three or four years, all erected with great care.
With the above situation prevailing, failure of any section of your antenna can be a major calamity, involving much property damage for which you may be held responsible. A 2 × 4 falling four to six stories is something of a monster, and can easily kill from that height. We must take steps to prevent any such calamity.
A major problem to contend with is the erosive soot:from incinerator outlets, and the smoke and soot from the surrounding apartments. The fumes cause such serious rust and erosion that TV masts and antennas literally turn to dust unless steps are taken to protect the surface of the metal. Aluminum is supposed to be corrosion-resistant, but minor impurities in the metal are acted upon, causing a galvanic action which eats away at the metal until it looks like a moth- ridden garment. Television masts look like castaway cigars. I have devised a few simple precautionary measures, some old and some new, which can avert a catastrophe of major proportion.
A few months ago a very bad storm fractured a 2 × 4 which supported a two-meter array. This entire structure was hanging more than 36 feet over the parapet. Without protection this could have fallen into the street, with serious consequences. A simple measure secured this mast and prevented it from falling. It is now among the residents of my antenna graveyard.
A good antenna is hard to come by for us cliff dwellers in the city. It should therefore be erected with loving care, and watched carefully so that roof privileges will not he withdrawn.
Breakage of insulators
My flat top is 140 feet long, of No. 8 Copper-Weld wire. You have only to hold the far end to realize the amount of pull it can exert if suddenly dropped. In case of failure, I use the method outlined in Fig. 1. Several lengths of 50 lb. test monofilament are braided together and strung through the center insulator and the first spreader which is placed about six inches below the center insulator. If you are a fisherman, you may have this type of line; if not, scrounge it from a friend who has it. The end insulators are also bridged in the same way. If the insulators break, the monofilament braid will take over and break the fall. This stuff is strong and impervious to the weather, so have confidence in it. Secure the ends with a figure-eight or a bowline knot and make sure the knot is secure.
Fig. 1. The braided line will hold the antenna temporarily should the insulator break. Material having suitable insulating characteristics should be used for the line, as suggested in the text.
Fig. 2. A Y-bracket holding a brass-pipe roller is more reliable than most pulleys and makes it possible to rethread a halyard without lowering the mast. Pipe clamps can be used to fasten the mast against masonry and the tarred block protects the roof.
Halyard failure
This danger can be minimized by using at least Minch or -irich Manila or nylon rope. This should be checked at regular intervals, and replaced before it breaks. Tape the first three feet after the end insulators. This will prevent cutting when tightening your halyards. The halyard should be secured by spiraling it around the mast. This will serve as a shock absorber, and take up the slack. Be sure to use a length at least twice the height of the mast.
To keep the antenna from falling if a halyard does break, run a second halyard at each end. This may be of smaller size, such as %6-inch braided nylon. This second set of halyards should be left slack, so as not to take any of the normal antenna weight, but the ends should be anchored securely.
After the antenna has been raised, tie the halyard ends as far up on the mast as possible, using a chair or stepladder. Then run the excess halyard ends to any secure anchorage that may be found on the roof. This will keep the mast from falling off the roof should the mast come down.
Pulleys? No! I have never seen the pulley that would stand up. Forget about them. Use a Y bracket made out of steel strap, as shown in Fig. 2. Your plumbing-supply house will make this cheaply. Secure the bracket to the mast with two through bolts and washers. I never did it, but it sure should help to put a length of brass pipe over the top bolt. This will keep the halyard from roughing up. I am going to do it if my masts ever come down. (Heaven forbid!) So my halyards get scuffed.
If you have to replace a halyard, it can be done very easily by using two lengths of bamboo from a rug, splicing them together by inserting one in the other, and fastening with wire and tape. This will give a height of over 24 feet. For additional height add a length of plaster lath strip, and notch the top. This arrangement is very light and can be handled by one man. Just raise the pole with the new halyard in the notch, and drop the line over the Y extension, and you are back in business.
Mast failure
Mast failure is caused either by poor materials, improper materials or poor installation. I have erected countless masts made of 2 × 3 inch and 2 × 4 inch sections. All have come down for various reasons, but the masts > supporting my present Zepp have been up for fifteen years and are still going strong. Wooden masts have to be guyed in the first place, and guy wires break, rust, sag, and the landlord doesn't like them anyway. Retention bolts and straps loosen because wood expands and dries out, the bolts either pull out, or the mast splits (just look in my graveyard). The fumes from the incinerator kill the guys, rot the wood, and just knock the devil out of it, so don't use wood unless you don't mind replacement every three or-four years. - Aluminum? Just look at the TV antennas on my roof. You can count more lying down than standing up. And - show me the aluminum mast that will withstand incinerator fumes. I have had them literally turn to dust.
What mast to use? I use 2½ inch galvanized iron-pipe masts, 12 feet each section, joined by a connector, and threaded for aTap on top and on the bottom. Your plumbing-supply house will do this for you too. Mine were old steam pipes. Treat your masts with loving care. Sand them to-remove any rust spots, give them three coats of chrome paint, then a few coats of outdoor white lead. It doesn't take long.
Be kind to your roof. Place a small piece of tarred wood at the bottom of the mast. This will prevent damage to the roof, and the block can be knocked out for any roof repairs, and the roofer will love you and not tell the landlord. The mast can be secured to brick parapets or pent hatches-with lag bolts and copper pipe strap. See Fig. 2. Paint these well, keep them painted, and please replace them every five years or so if they loosen, and they do. The lag bolts can be tarred, if you are so inclined.
Last, but perhaps most important, take out extended-coverage insurance. This is not expensive and will cover any unexpected- damages to person or property.
Myrton J. Billings, W2BIV.