Tuesday, January 21, 2014

Building your first wire antenna

So you want to get on the air.

When first setting up your ham radio station, most people wait until they can save up enough money to buy the best that they can afford. But in reality you don't have to wait to get on the air with a simple HF dipole desig.

Stringing up that wire antenna.

As you string up that fancy new dipole that you just read about in the latest ham radio magazine, wrapped in wire from head to toe in a tangled mess, you have to wonder if it is all worth it. with a tape measure in one hand and wire cutters in the other, you count out the required dimensions of that new design, in the hopes that once it is put up in the air, it will bring in all that exotic DX that you have struggled for over the last few years. So what happened ?

Wire antenna's are a great way to get on the air.

Wire antenna's are one of the best sources for radiating a signal out from your station on the lower HF bands, but they require a bit of work, height and real estate. You can go with a compromise antenna like a G5RV that will work reasonably well if you are strapped for grass and space, or build one of the other exotic designs that are spread out across the internet, like the Extended Double Zepp (EDZ) antenna that is two 5/8 wave antennas in phase with a vertical section made with ladder-line.
Not only do wire antennas perform well, but you get a sense of accomplishment after you have built the antenna and put it up in the air. It is even more of a thrill when in your first QSO and you get to brag about building the antenna yourself. You can of course, go online and purchase a wire antenna that will perform just as well as a home-brew antenna, but for the frugal ham radio operator this is not always an option

OK, lets get started.

Building a simple dipole for 40M

 The easiest wire antenna to build for a beginner is a simple mono band dipole, made out of just two pieces of wire. As you gain more confidence you can go for some of the more exotic designs that are out their, but for now let's concentrate on the dipole.
 A dipole is just a ½ wave piece of wire connected to your coax. You run one piece to the center conductor and the other side to the braid of your coax and you have a dipole. To figure out what band you want to make it for you use the equation:

468 / freq= Total length .

 SO, if you wanted to make a dipole for 40 meters in the CW portion of the band, you would just use 468 divided by 7.05 (Center of 40M band CW portion) which gives you a length of 68 feet. To get the size of each half just divide that by 2, giving you 34ft. How simple is that ?

 One of the nice features of this simple dipole is that it can be hung from a single mast or tree branch in an inverted-V configuration and still perform well. Just remember that if you put it in this configuration that you may have to do a little fine tuning since the proximity to the ground will affect the resonance.
One improvement that can be made is a simple RF balun made out of 8 turns of your coax right before it connects to the antenna. This keeps the coaxial from radiating and will reduce interference.

 If you have a friend with an antenna analyzer then you can fine tune the wire antenna for your yard. Other factors include the ground soil for your QTH and the diameter of the wire that you use, but overall this equation should get you in the ball park and on your way to making contacts over the airwaves.

Get on the air and start making contacts.

Of course, since every setup is a bit different YMMV, but this is a good start. As you get more involved with Amateur radio you can make a lot of improvements to your station, but this simple dipole antenna will get you on the air and started making Domestic and international contacts with Ham radio operators.
 See you on the air

P.S. If you really do not want to bother making your own dipole then purchase a wire antenna at Amateur Radio Supplies.
*HINT* Use CouponCode 73 for an additional 10% savings.