NEW DIRECTIONS RADIO

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The signal will more often than not pass over them, that is, if it weren't for an interesting phenomenon. Figure 2 shows what can happen at various times in the 3 to 30 megahertz (3,000 to 30,000 kilohertz) range. The atmosphere 50 to 200 miles above the earth becomes ionized: that is, the intense solar energy which bombards the earth is able to pry electrons off the few gas atoms floating around at that altitude. This charged ionosphere acts like a mirror to the energy of certain frequencies arriving at certain angles, and bounces the transmission back down to the planet's surface. There it may be picked up by a receiving antenna and/or reflected off the globe back toward the ionosphere. Under optimum conditions, transmitted signals can bounce halfway around the world via multiple reflections.

Which frequencies will be reflected, and how much energy will be lost in the "mirror", depends on the time of day or night, latitude, season of the year and various happenings on the sun. Solar flares mess up transmission. Sunspots are helpful, but come and go in an 11-year cycle. Since we're approaching the worst part of their current period, there are only three amateur bands particularly suited to New Directions Radio at the present time (as compared to five useful bands at a sunspot maximum).

What we can expect in the way of radio wave propagation —transmission characteristics—on these three bands is summarized in Table 2. (Note the poor coverage of nearby areas in many cases: The signals actually bounce or skip over adjacent territory and return to earth at a greater distance.) Each of the bands is split up into smaller sub-bands according to class of license and permitted modes of transmission, but propagation is fairly uniform on all frequencies within a given range.

So much for the transmission of a raw signal. Now let's make this "carrier" take a message along with it. The process of adding intelligence to the transmitted energy is called modulation and here are the more popular variations:

MORSE CODE OR CW gives the most miles of transmission per watt of transmitter power under normal conditions. It also requires the simplest and least costly equipment. The main disadvantage is the slow rate of information transfer...as few as five words per minute for a beginning novice, up to 20 or 25 wpm for a very proficient operator. (Now you know why all those dumb abbreviations used by ham operators got started!) In sending code, the telegraph key simply turns the transmitted energy on and off.

VOICE OR PHONE modulation is much more popular today than any other mode of ham operation. Modern single sideband (SSB) transmitters simply take the natural audio frequencies of the human voice (300 to 3,000 hertz) and move them to a frequency in an amateur band: 14,200,300 to 14,203,000, for example. The miles per watt of "reach" with this method are not as great as with code, although the system has much better range than commercial stations generally realize in the AM broadcast band. The disadvantage of SSB is that the signals sound un intelligible—like Donald Duck—unless carefully tuned in on a receiver designed for single sideband reception. (Most portable shortwave receivers, for example, do not have the necessary BFO—beat frequency oscillator —to make SSB-carried voice understandable or SSB-modulated code audible.)

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