Antenna basics
Before looking at the various antennas we need to look at some of the basics
of antenna systems. In this chapter you will learn some of these basics. And
while they will not make you a red-hot professional antenna engineer they
will set you up well enough to understand this book and others on amateur
and hobbyist antennas. We will look at the matter of antenna radiation,
antenna patterns, the symbols used to represent antennas, voltage standing
wave ratio (VSWR), impedance, and various methods suitable for constructing
wire antennas in the high-frequency (HF) and very high-frequency
(VHF) regions of the spectrum.
ANTENNA SYSTEM SYMBOLS
Figures 2.1 and 2.2 show the various symbols used to represent antennas
and grounds. The reason why there are so many variants is that there are
differences from country to country, as well as different practices within any
one country (especially between technical publishers). As for antenna symbols,
I see the symbol in Figure 2.1C more often in the USA, but Figure
2.1B comes in for a close second. The supposedly correct symbol (endorsed
by a professional society drawing standards committee) is that of Figure
2.1A – but it is only occasionally seen in the USA.
The situation for grounds is a little different because some differences
reflect different forms of ground (although some of the differences also
represent national or publisher differences). The ground in Figure 2.2A is
usually found representing a true earth ground, i.e. the wire is connected to a
