Kevlar Antenna Wire: As Good as It Seems?

My first contact with Kevlar-reinforced antenna wire came when I bought one of Geoff Brown's (G-Whip) end-fed units many years ago, where it was said to be "essentially indestructible."

Kevlar-cored wire.  Light and strong, but not indestructible.

For sure, this wire is tough.  You can pull away at it with pliers, probably have a good go at pulling a car with it (not recommended, of course!) and it is relatively easy to work with.  It has a good resistance to forming tangled messes of wire, a definite consideration for any portable working!

Most of all, Kevlar is lightweight - up to three times lighter than PVC-covered Flexweave.  That's a major consideration when you want to prop up an antenna with a fairly simple fishing pole, none of which can carry very much weight.

Using Kevlar wire is a little fiddly in that you have to first strip away the outer plastic as normal, which leaves you with a densely wound layer of very thin copper strands that is much the same as a coax outer braid, and then the Kevlar core fibres.  The fiddly bit is that to solder the wire, you have to pull back the braid, and then cut the Kevlar fibres just ahead of the braid with some very sharp scissors; blunt ones will just make a mess of the wire and fail to cut the tough material.  This leaves a short length of solderable wire with no Kevlar in the way.

Sometimes, the braid gets mixed up with the Kevlar core, which usually means you have to cut that bit off and start again.  The problem with the Kevlar being in the way of any soldering is that it absorbs heat and contaminates the joint to be made, such that you end up with a stubbornly unsolderable joint.

You can of course rely on just compression of the wire to a spade connector or such like, where removing the Kevlar core isn't necessary.  But I always prefer to have some degree of soldering.

Make some strain-relieving loops at connection points.  If you cut a backwards slot in dipole centres and insulators, you make removing and replacing wire infinitely quicker and simpler!

Don't rely on a belief that this wire, often marketed as ''mil-spec" is immune from failure, though.  I've had a delta loop up for four years or so, and after that time, there have been a couple of failures of the conducting braid, generally at corners where there is higher stress.  Some of the strands appear to fail from metal fatigue, which slowly deteriorates to the point of an unstable SWR due to an intermittent continuity.  Arcing is evident in all the failures, which slowly burns away the Kevlar, too.

A badly failed corner of a delta loop, where arcing has burned the strengthening Kevlar core away.  In fairness, it took more than four years and countless gales of wind to reach this point.

So, if you're mounting some wire, make sure you incorporate a couple of loops at the end of the wire that connect to insulators or dipole centres.  This leaves a tail that you then connect to the transmission line, but isn't subject to most of the strain put on the rest of the wire.  If you don't do this, even a Kevlar wire will very soon fail at the point of joining to a spade connector or similar.

To conclude, then, Kevlar is worth buying because of the considerable weight saving and, if you are blighted by heavy winds, less wind-catch area.  In terms of its physical durability, whilst it is very strong, it isn't at all immune from failure.  Properly installed, stress-relieved Flexweave or even drawn copper is likely to last just as long, if not longer, provided you can accommodate the extra weight and/or stiffness of those wire types.