and wavelength somewhat interchangeably. (The 40 meter and 7 MHz ham bands are the same thing, for example.) I use both terms in this book so that you become used to interchanging them as hams are expected to do.
Dealing with Mother Nature
Ham radio offers a whole new way of interacting with the natural world around us. The movement or propagation of radio waves is affected by the Sun, the characteristics of the atmosphere, and even the properties of ground and water. We may not be able to see these effects with our usual senses, but by using ham radio, we can detect, study, and use them.
Experiencing nature affecting radio waves
Ground wave propagation: For local contacts, the radio wave journey along the surface of the Earth is called ground wave propagation. Ground wave propagation can support communication up to 100 miles but varies greatly with the frequency being used.
Sky wave propagation: For longer-range contacts, the radio waves must travel through the atmosphere. At HF and sometimes at VHF (refer to “The radio spectrum,” in the previous section), the very highest layers of the atmosphere, called the ionosphere, bend the waves back to Earth. This is called sky wave propagation or “skip.” Depending on the angle at which the signal is reflected, a sky wave “hop” can be as long as 2,000 miles. HF signals often bounce between the Earth’s surface and the ionosphere several times so that contacts are made worldwide.
Tropospheric propagation: Apart from the ionosphere, the atmosphere itself can direct radio waves. Tropospheric propagation, or tropo, occurs along weather fronts, temperature inversions, and other large-scale features in the atmosphere. Tropo is common at frequencies in the VHF and UHF range, often supporting contacts over 1,000 miles or more.
Aurora: When the aurora is strong, it absorbs HF signals but reflects VHF and UHF signals while adding a characteristic rasp or buzz. Hams who are active on those bands know to point their antennas north to see whether the aurora can support an unusual contact.
Meteor trails: Meteor trails are very hot from the friction of the meteoroid’s passage through the atmosphere — so hot that the gases become electrically conductive and reflect signals until they cool. For a few seconds, a radio mirror floats high above the Earth’s surface. Meteor showers are popular times to try meteor-scatter propagation (see Chapter 11).
Overcoming radio noise
One limiting factor for all wireless communication is noise. Certainly, trying to use a radio in a noisy environment such as a car presents some challenges, but I’m talking here about electrical noise, created by natural sources such as lightning, the aurora, and even the sun. Other types of noise are human-made, such as arcs and sparks from machinery and power lines. Even home appliances make noise — lots of it. When noise overpowers the signal, radio communication becomes very difficult.
Radio engineers have been fighting noise since the early days of AM radio. FM was invented and used for broadcasting because of its noise-rejection properties. Even so, there are practical limits to what transmitters and receivers can do, which is where digital technology comes in. By using sophisticated methods of turning speech and data into digital codes, digital technology strips away layers of noise, leaving only the desired signal.
physics.princeton.edu/pulsar/K1JT.
Chapter 3
Finding Other Hams: Your Support Group
IN THIS CHAPTER
One of the foundations of ham radio is helping newcomers. After all, a ham radio license is mostly a license to learn! Hams are great at providing a little guidance or assistance. You can make your start at ham radio operating much easier and more successful by taking advantage of those helping hands. This chapter shows you how to find them.
HAM RADIO — MEETING ONLINE
As this edition is being written, Covid-19 continues to require social distancing, so many face-to-face ham radio events have been canceled. For now, the hamfests, meetings, conventions, and conferences described in this chapter are still happening, but only online. Many hams are taking advantage of the situation to watch the many presentations and seminars now available to an online audience at little or no cost. The success of this format means you can expect to find many “virtual” events available in the future.
Finding and Being a Mentor
A mentor is very useful in helping you over the rough spots that every newcomer encounters. A good place to start your search for a mentor is to search for ham radio clubs in your area (refer to “Finding and choosing a club,” later in this chapter). You might start on the clubs page of the QRZ.com website (go directly to
