Antennas are the last frontier of the average DIY ham skills, and they are the most important part of the hobby. You can purchase the best gear money can buy, but with out an antenna, it’s useless.
The most common antenna projects are wire antennas for HF, but least not forget about the VHF/UHF projects as well. In this section, we’ll look at home brew and DIY antennas.
HF antennas can be very large, it’s often difficult to find space for one at first glance, but, with some thought, and creative engineering, you can do it, you just need to think outside of the box. No trees for support, How about a vertical? Live in an HOA with a cranky neighbor? No problem, we can hide the antenna or use what we already have, rain gutter and down spouts work great, flag poles, garden fence, or many other object that appear to be something else.
So, lets start with a simpler situation and work from there.
Lets say you live in a rural area, you have plenty of land and no restrictions, then the sky is the limit, or maybe gravity is the limit in this situation. If you can dream it and afford it, then only the limits of the structure limit what you can do, but, for those of us that do not have Scrooge Mc Duck’s money and miles of open sky, then we need to real our dream in, just a bit.
Let’s consider the urban ham, he or she may have only a city lot in which to build their antennas. This is the common challenge that faces most hams, and one that has been tackled time and time again, so rather than reinvent the wheel, we’ll learn or copy what others have done, and maybe along the way, we’ll learn a few things, make improvements, or discover something new. Just because someone says it will not work, doesn’t mean it will not work for you, you can still try, and also, because you haven’t heard of someone else trying, doesn’t mean you shouldn’t try, at least as long as what you attempting to do is safe for you and others around your antenna system.
The most common antenna is the dipole. It’s simple to make, effective, and can be the most bang for your buck. If you make it as a “doublet” it becomes a multi band dipole with the aid of a tuner, preferably a balanced unit, but any tuner with enough range and the correct balun can get you on several bands with a doublet antenna where as the simple dipole feed with coax is likely limited to one or two bands if the second band falls into a harmonic. One may also construct a fan dipole, this is a dipole with multiple dipoles connect to a common feed point. It is of my opinion, many times these “fan dipoles” are built upside down, meaning the builder often starts with the longest antenna then adds the smaller one under it, this works and it easier, but having built several in a reversed fashion, the smaller antennas worked better higher up being on top and being flat verses an inverted v configuration.
Another common antenna is the random length wire. This almost always needs a tuner, but, if can work many bands when used properly, this also holds true with end fed half wave antennas. Both of these antennas require some sort of matching device at the feed point, usually called a balun, meaning balanced to unbalanced, typical on coax fed antennas, or you may need and unun, a transformer that matches unbalanced to unbalanced. There is also RF chokes or ugly baluns to consider in the use of these antennas.
I’ll be adding more soon, so please stop back again.