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--- howto:hambasics:temp [2019/11/25 15:54] – created ve7hzf
+++ howto:hambasics:temp [2019/11/25 18:32] (current) – removed ve7hzf
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-====== Amplitude, Wavelength, Period, and Frequency ======
-''Picture of travelling 2m wave''
-Imagine that the dot moving up and down is creating the wave that's travelling to the right.
-Look at the following two waves.  How are they different?
-{{wave1.png?400}}{{wave2.png?400}}
-At first sight:
-  - the first one is "taller" than the second one.  That is, it goes up and down higher and lower.
-  - the first one is also "longer" than the second one.  That is, it stretches sideways more.  It's not as "tight".
-These two observations can be quantified very precisely as:
-  - the //amplitude//: **vertical** height from the centre of the wave to its highest (or lowest) point.
-  - the //period//: **horizontal** length of one complete cycle.
-{{  wave3.png  }}
-So the previous two waves have:
-  - Amplitude = 2, Period = 0.05 ms
-  - Amplitude = 1, Period = 0.02 ms
-{{wave1.png?400}}{{wave2.png?400}}
-The amplitude is normally related to the strength of the signal (like the volume for sound).
-Since the period (//T//) is the amount of time it takes to complete one cycle, and the frequency (//f//) is the number of cycles in one second, the period and the frequency are inverses of each other:
-<latex> \qquad  $$f = \frac{1}{T}  \qquad  \Leftrightarrow   \qquad T = \frac{1}{f}$$</latex>
-<box 80% blue>
-In this course, we'll see a few formulas and it'll be tempting to memorize them but let's instead understand what they really mean...
-</box>
-For example:
-  * if the period is half a second, we can fit 2 full cycles in one second.
-  * If the period is a quarter of a second, the frequency is 4.
-  * If the period is a tenth of a second, the frequency is 10.
-  * If the period is T seconds, the frequency is $\frac{1}{T}$ ( $\frac{1}{0.5} = 2,  \quad \frac{1}{0.25} = 4, \quad \frac{1}{0.1} = 10$ )
-Right?
-So for the previous two waves, the frequencies would be:
-  * <latex>$$f = \frac{1}{0.05 \text{ ms}} = \frac{1}{0.00005 \text{ s}}$$</latex> = 20,000 Hz = 20 kHz
-  * <latex>$$f = \frac{1}{0.02 \text{ ms}} = \frac{1}{0.00002 \text{ s}}$$</latex> = 50,000 Hz = 50 kHz
-Recall that //Hz// means "cycle per seconds".  That's why when we divide a number of cycles by time, we get Hertz.
-Let's now look at three different ways to encode a signal on a radio wave.
-FIXME: add $f=\frac{c}{\lambda}$