Wire Antenna Life

How long should a wire antenna last?

The answer to the question depends on many factors. Some are under your control, some are not. To quote some ancient ham radio wisdom, "if it didn't fall down last winter, it isn't big enough!" Let's look at two scenarios:

MADE TO LAST

This first station has two unguyed, free standing 80 foot towers about 150 feet apart. Directly between the two towers is a 100' wooden pole. A wire dipole is strung between the two towers. Its center insulator is attached to the wooden pole that supports the weight of the heavy coaxial feedline. The towers are high quality units and do not sway even in high winds. The wire used in the antenna is #10 stranded copper-clad steel. Three insulators are at each end of the antenna. They are connected in series with stainless steel wire using the proper stainless steel wire clamps. The support line is stainless steel wire rope that runs through commercial quality stainless steel pulleys attached directly to the towers. The antenna support lines run through the pulleys and down the tower where they are terminated with heavy weights and dampening devices.

 

The dampening devices act like 'shock absorbers' to keep the weights from moving or dropping too quickly during sudden wind gusts. The weights and dampening devices are supported by ground anchors secured by the tower's concrete base. There is constant tension on the antenna wire even in high winds. Extensive weatherproofing techniques are applied to the entire antenna and feedline system including the balun/center-insulator that costs around $500.

A very long, maintenance free life can be expected from this antenna. It was put up for government use.

. . . . MADE TO GET BY

This is the installation at a fictitious amateur radio station, but is typical of many such installations.

#14 house wire is stretched between two trees. A length of utility nylon rope is thrown over easily available tree limbs. The antenna is directly supported by the nylon line. The insulators used are cut from a sheet of plexi-glass, and are used as "end" insulators and as the center insulator. The coax was stripped back about one foot and the braid and center conductor are soldered directly the antenna wire elements. Inexpensive vinyl tape seals the coax. There is about a 10 foot sag in the middle of the antenna due to the weight of the coax and the ever stretching nylon line.

 

The trees will sway and stretch the soft household-type wire. Antenna resonance will move lower and lower in the band. Antenna sag will increase. In a few days, someone will untie the ropes from around the tree trunks and pull the antenna back up to its original height. The nylon lines scrape across the tree limb and begins to abraid. Along comes a storm and the trees sway violently in the wind. The antenna, attached to the trees resists the motion. The force is terrific and the antenna wire stretches. The nylon rope is sawing back and forth over the tree limbs. Water is entering the coax since only electrical tape was used for weatherproofing. Finally, abrasion take its course, cuts the nylon line, and down comes the antenna.

Is this an unusual example of a ham radio antenna installation? Probably not.

Will this antenna still be up next year this time? Probably not.

An Alternative

A RADIO WORKS CAROLINA WINDOM® is supported between two trees. 3/8" Dacron line runs over the tree limb and terminates in a quality sailboat pulley with a roller designed for 3/16" line. The pulley is equipped with a swivel. 3/16" Dacron line, tied using proper knots, runs through the pulleys, down the side of the tree and is securely tied to a heavy garage door spring, Bungee chords, or other strain-relieving device. The strain-relief device keeps tension on the antenna as the trees to sway.

The antenna is a standard, out-of-the-package, CAROLINA WINDOM® 80, made with #14 hard-drawn copper wire. The end insulators are of high quality, are strong, and are deeply ribbed. The center insulator is the matching unit made for the CAROLINA WINDOM®. This device features stainless-steel eye-bolts and a silver plated coaxial connector. Pressure connections are not used to connect the antenna wire to the windings inside the matching unit. Instead, wires from the windings in the matching unit exit the case and are soldered directly to the antenna wire elements. Coax Seal™ is supplied with the antenna for proper weatherproofing. The coaxial Vertical Radiator has molded-on strain-relief so that it can bare the weight of the Line Isolator™ and the coaxial feedline.

We have had reports that the unmodified CAROLINA WINDOM® has served its owners for as long a 20 years. Several reports have come in claiming continual use for over 15 years. It always amazes me when I get these reports. As you will see below, with proper installation and yearly inspections, your antennas can last for many years, too.


An antenna installation alternative used at W4THU

I don't use tensioning devices (springs, Bungees, or weights) because I think they can be dangerous. Certainly they are a nuisance. Instead, I use long lengths of Dacron support line. I make my my antenna support ropes as long as possible. Typically, my support ropes are at least 100 feet long on each end of the antenna. Using long support ropes is simple a simple solution, but the technique may not be practical or appeal to everyone.

Nothing could be simpler, I just run my support lines from one end of the antenna, through the marine-grade pulleys held near the top of a tree using 3/8" Dacron rope. I use only single-braid Dacron. I found that the double-braid, jacketed, variety did not have as long a useful life as the single-braid type. Instead of tieing off the end of the 3/16" single-braid Dacron rope, attached to the end of the antenna at the base of the support tree, I run the 3/16" support rope all the way back to the tree supporting the other end of the antenna. I do this at each end of the antenna. What you end up with is an antenna strung between two trees and lots of support rope forming an "X" shape between the trees .

In recent years, I have modified this technique slightly and bring the ends of the two support ropes back to a central location. This permits easy installation of new antennas and makes it easy to lower the antenna for adjustment.

In most of my antenna installations, the 3/16" support rope is over 150 feet long on each end of the antenna. Thus I have 300 feet or more of Dacron line holding the antenna in place. Dacron line can stretch quite a bit before being being permanently stretched. The result is a self-springing action which is very reliable, tolerant of high winds and the resultant tree movement.

If it's not practical to run the 3/16" support rope all the way back to the opposite support tree, use some intermediate tie-off point. Both support lines can be tied-off at this point. This makes it very easy to work on your antennas since both the ends of the both support ropes are accessible from the same location on the ground.

Perhaps these graphics will be helpful.

A simple, but effect antenna installation method

Above is the installation method I've recommended for years. It is perfect for many installations. However, if there is a lot of tree sway, then some sort of strain relief must be provided to prevent the swaying trees from breaking the antenna wire or ripping the support ropes out of the trees limbs. Pulleys are definitely recommended. Use only marine types with swivels. The pulley support is identical in each of these illustrations. It is a 3/8" Dacron rope, supported by a tree limb, and tied off at the base of the tree. The pulley support line is not supposed to move. That is why the 3/8" Dacron rope is used. It's resistance to stretch is several times higher than the 3/16" rope used to support the antenna itself.

In every installation, the length of the 3/16" antenna support rope must be long enough for both ends of the rope to reach the ground. This is necessary so that you have access to each end of the rope at ground level so that you can tie one end to the antenna end insulator and have the other end available to pull the antenna into the air. The excess rope is tied off at the base of the tree, after the antenna is pulled into the air. The pulley is held in place with a length of 3/8" Dacron line. This large line has much less stretch and thus does not move across the supporting limb(s) which would abraid the rope and cause it to break.

 
A more elaborate system provides the needed strain relief by using long support lines which act as springs.

This is an ideal system for installing wire antenna systems. It uses very long 3/16" Dacron antenna supports lines which permits trees to sway many feet with out affecting the antenna or putting too much strain on the antenna wire which could cause it to break.

In this system, the antenna support ropes are brought back to the opposite end support (tree, etc.) and is tied off there. Thus, each antenna support rope is longer than the antenna itself. The long 3/16" support rope has enough stretch to protect your antenna from excessive tree sway.

The pulley support line is the same as in the first illustration.

 
A compromise system suitable for most back yards.

This is the system I currently use. I have three similar installations. Two support antenna 50 feet in the air and are used for antenna test purposes. The third installation supports an antenna at 90 - 100 feet above ground. The 50 foot supports could be higher, but that are specifically set at that height because it is more typical of most installations. This is the height above ground used in the development of most RADIO WORKS antenna systems.

Since all of my antennas are high above the ground, it isn't necessary to run the ends of the 3/16" support line back to the opposite support. Instead, I tie them off at a central location half way between the support trees. The tie off point is not directly under the antennas, but is offset by some distance to prevent tangles when antennas are lowered. Another useful thing about this technique is that I can adjust both ends of the antenna from the same location. This is very convenient and the visual impact is not all that bad. It's nice to be able to drop an antenna for adjustment in just a couple of minutes. I can completely change an entire antenna system in five to ten minutes.

This system has survived three hurricanes, though I must say that highest of my antennas did come down during the last hurricane. The ropes and wires didn't break, the top of the tree broke off and a hopeless tangle of wire, rope and tree limbs was the result. The worst of it was that I lost twenty feet of antenna height. With that extra twenty feet of height, I'd have one antenna system at 120 feet. That would be very nice!

Again, the 3/8" pulley support line is the same as in the other illustrations.


If you use the first technique shown above, a 'rope fuse link' can be installed to prevent overloading the springs or other strain relief during a heavy storm. This 'rope fuse link' works like an electrical fuse. When the wind loads reach a high enough level, the 'rope fuse' opens to protect the antenna support system. The antenna falls harmlessly several feet and that allows for more tree movement before the springs are over-stretched.

To make a 'rope fuse link,' tie two loops, several feet apart, along the length of the antenna support rope. To avoid tangles in the tree, this is done at a point between the antenna and the tree. You may want to use wire rope 'thimbles' to reduce wear on the rope and 'fuse link.' Select thimbles that have smooth surfaces. Between the loops in the antenna support rope, tie a 'fuse line.' The line used for the 'fuse link' has a 'test' strength of only 25% to 35% of the main antenna support rope. The idea is that the 'fuse line' will stretch and break long before the antenna support line breaks.

The coax used in our alternative example is light weight RG-8X or Super 240. Strain-relief is is applied as outlined in the Product Manual, packed with the antenna or available at our web site (www.radioworks.com). All recommended weatherproofing procedures, including CoaxSeal® and weatherproof vinyl tape are applied.

A system improvement would be to support the antenna at its middle. This would provide strain relief due to the weight of the coax.

To reiterate, the antenna used in these scenarios is an off-the-shelf CAROLINA WINDOM® 80, constructed using our standard, high quality, #14 hard-drawn copper wire. All connections are soldered. Heat shrink tubing covers the soldered joints to provide weather - proofing and reduce the corrosive effects of the atmosphere. End insulators are deeply ribbed and are self cleaning in the rain. The matching transformer at the feedpoint uses stainless-steel eye-bolts. The eye-bolts are not internally connected which reduces any receiver noise caused by the contact of two dissimilar metals (stainless steel eye-bolts and copper antenna wire)

This installation should provide several years of reliable service.

By the way, if you want an antenna constructed for very heavy duty conditions, we can custom build some of our antenna systems for you. You can select the wire size and type of your choice (our #13 stranded, insulated, copper-clad wire is a popular and recommended choice).

The increased wire strength and insulation may be worth the extra cost, especially if you live where bad weather is a critical factor.

So, how long does a wire antenna stay in the air?

There is no easy answer. Put up an antenna properly as described above and you can expect many years of trouble free operation. A typical ham radio antenna installation, using trees for supports will probably last a few years or until a big storm comes along. Adding preventive measures like long support lines will probably add several years of useful antenna life. The antenna will propbably last much longer than the support rope which should be changed periodically.

Antenna supported from towers may perform less well than tree supported antennas but give extra years of service. The interaction between the towers and the wire antenna depends on many factors. The guy wires in particular may affect the antenna supported by metal towers. Use low quality parts and poor weatherproofing techniques and you should expect a short service life from your antenna installation. Quality parts and proper installation will reward you with many years of useful service.


Wire antennas are not forever. Installation and quality are major factors in the useful life. Don't forget maintenance. You can avoid an untimely failure.


How long should an antenna stay up?

Ralph's Law -

Only until it falls down, of course!

It's an extension of the old rule: "If it didn't fall down last winter, it wasn't big enough!"


Premium Antenna Parts

Keep your antennas in the air!

We offer a wide selection of high quality antenna parts. Here are some of the parts you want to use in your ultimate wire antenna system.

#13 Insulated, 19 strand, copper-clad steel wire or multi-strand insulated antenna wire.

RG-213 Plus or Extra-Flex Low-loss coax.

Premium Quality RG-8X, RG-8X PLUS, or our highly recommended Super 240.

Heavy Duty Ladder-line with #16 or #14 stranded copper-clad steel conductors.

B1-5K Balun, or any RADIO WORKS balun

Mil-spec 3/16" Dacron® support line combined with a pulley system. 3/8" mil-spec Dacron® rope to hold the pulley in a tree or other support.

CoaxSeal® and other parts in our "Weatherproofing" section. See Weatherproofing Kits.

Silver Teflon® insulated PL-259 connectors with Teflon dielectrics.


Yearly Wire antenna maintenance.

Support ropes

You need to check out the entire length of all support ropes. This is especially true for ropes that contact tree limbs or any place that can cause abrasion. Also, don't overlook the fact that Squirrels and other tree creatures like to chew on ropes. I have found, after many years of experience, that the double-braid support rope does not stand up as well as our 3/8" Dacron® mil-spec rope when supporting pulleys in trees.

Compare the support rope with a piece of the same rope that has not been in the sun and weather. Note how fast the material is deteriorating. Does it feel stiffer? Does it's color look dull? Are strands breaking? If so, consider replacing the support lines.

End Insulators

Wash all the dirt, spider's webs, and other accumulated junk off the insulators. Check to see if they are cracked.

Wire

If the antenna is made of copper-clad steel wire, is there any sign of rust? Are there broken strands? Is the copper in good shape? Does it have any cracks in it? Pay careful attention at the end insulators and the matching transformer or balun eye-bolts. This is where most of the damage to the wire will take place.

Soldered Connections

If you are not using a RADIO WORKS antenna, check all soldered or compression connections. Do soldered connections look crystallized? If so, re-solder them with quality solder and extra flux. You may want to weatherproof the soldered connection. Apply a layer of CoaxSeal® over the newly soldered connection.

Balun or Matching Transformers.

Check the weatherproofing. Is it still intact? Is there water in the balun's or matching transformer's case? Water doesn't generally harm a balun or matching transformer, but it might be a good idea to let the water out. Drilling a small hole in the TOP of the case will permit pouring or shaking out the water. Reseal the balun according to instruction manual directions. Plug the newly drilled hole with a ball of CoaxSeal® pressed firmly into the hole. Hot melt glue works, too.

Coax deterioration:

If you really want to do a first-class inspection, disconnect the coax from the antenna and measure the coax for power loss.

Here is the procedure. Put a dummy load at the antenna end of the coax. Measure the transmitter output power, using an accurate wattmeter placed at the transmitter end of the coax. Move the wattmeter to the dummy load end of the coax and install it there. Reconnect the coax to the transmitter and without changing any of the transmitter's settings measure the power delivered to the dummy load. Record the two numbers and determine the loss of power through the coax. If the measured value is not within a few percent of the cable's specifications, replace the coax - period.

The Once Over

Give any other part of the antenna system a good examination.

Reinstall the antenna


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