The Art of Amateur Radio by Ron Hashiro, AH6RH and the (Emergency Amateur Radio Club) Wireless Dispatch.
Last month, we took a look at the key element of radio waves…that the major component of a radio wave is really a spreading, magnetic wave and while it may diminish over great distances, it never really disappears. So, let’s see how we can apply what we’ve learned to further our enjoyment of amateur radio.
You might be thinking that radio waves is a kind of black magic that can’t be seen, and therefore can’t be well understood. That’s not really true. If you imaging and look upon radio waves as a kind of light wave, you’ll soon be able to anticipate and predict it’s behavior. It’s so much fun to work directly on simplex, trying out different things, and being amazed when the results are different than what you expected.
If you think of light waves, there are three basic things you can do to with it: radiate, reflect and refract it. The same is true of magnetic or radio waves.
First off, let’s take a look at radiation and the impact of water upon radio waves. The rate that water absorbs radio waves varies with frequency. On the VHF and UHF bands, surrounding vegetation absorbs and affects propagation. Imagine the antenna as a light bulb, and the surrounding plants as a shield blocking your bulb. As you scan around your neighborhood, you can visualize how many plants there are near ground level that affect your “lighthouse view”. Therefore, it is time and money well spent to get an antenna on the roof, or at least above the surrounding plants.
Now, let’s take a look at ways you can reflect radio waves in everyday life. The wavelength of a two meter signal is about six feet. Therefore, if you aim a signal at a suitable object at least six feet square, you can get it to bounce in a new direction. If the object is above you, you can use it to extend your communications range. In effect, it would be the same as if you had moved higher location with a less efficient radio. It can work to your advantage at times.
If you find that a tall building is blocking your signal, you can use it to your advantage. Just go to the other side of the building, and use it as a reflector! The taller the building, the better the reflector. Even if the face of the building is not perfectly aligned with your target, the building features such as windows and railings may reflect enough signal to improve the QSO.
One of my favorite amusements is to use overhead freeway signs to provide a momentary boost in signal. To see how well this works, have another person on simplex that is behind you transmit as you drive under the signs and watch as the signal on your S-meter rise and fall as you pass each sign.
You can amuse your counterpart by letting him/her know that you will predict when your signal strength will increase. The signal reflecting off the sign will be momentarily stronger than the direct signal, and after a while, you’ll get the hang of predicting when the signal will peak. If you use UHF, you can use even smaller objects as suitable reflectors.
Even the mountains that comprise our valley walls can be an asset. Much of our rock is iron-based minerals and can be used to bounce signals out of a valley.
If you can see large, flat objects as mirrors of varying size and quality and view each other’s radios as lanterns, you begin to see all kinds of opportunities around you to bounce radio signals and extend your range. That is part of the art of amateur radio that is built upon science. Next month, we’ll look at refracting radio waves.