howto:hambasics:sections:polarization
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howto:hambasics:polarization [2019/11/26 07:04] – [Effect on Communication] ve7hzf | howto:hambasics:sections:polarization [2020/10/07 08:08] – va7fi | ||
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====== How To Make A Radio Wave ====== | ====== How To Make A Radio Wave ====== | ||
- | Back on the [[intro#hz |Intro Page]], we introduced to the idea of frequency and saw that | + | Back on the [[intro# |
- | >A Hertz (Hz) is a measure of how fast something vibrates [...] | + | <WRAP indent prewrap 80%> |
- | > | + | A Hertz (Hz) is a measure of how fast something vibrates [...] |
- | >Just seeing “Hz” doesn' | + | |
- | > | + | Just seeing “Hz” doesn' |
- | >Radio waves are created by oscillating electric currents. How many times this current oscillates per second is called the frequency, which is measured in Hz. | + | |
+ | Radio waves are created by oscillating electric currents. How many times this current oscillates per second is called the frequency, which is measured in Hz. | ||
+ | </ | ||
It's now time to add a few more details to this story. | It's now time to add a few more details to this story. | ||
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- Connect the two middle ends to each side of an alternating current generator. | - Connect the two middle ends to each side of an alternating current generator. | ||
- | {{dipole.gif}}{{radiationpatternh.jpg}} | + | <WRAP centeralign> |
+ | {{..:dipole.gif}}{{..:radiationpatternh.jpg}} | ||
+ | </ | ||
Voila! The antenna we've made is called a // | Voila! The antenna we've made is called a // | ||
+ | {{ youtube> | ||
====== Horizontal vs Vertical Polarization ====== | ====== Horizontal vs Vertical Polarization ====== | ||
- | {{ polarization.jpg}} | + | {{ |
Here's the critical part though: | Here's the critical part though: | ||
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====== Wavelength and Antenna Length ====== | ====== Wavelength and Antenna Length ====== | ||
- | As we saw previously, the wavelength (λ) in metres of the wave is dictated by the frequency | + | As we saw previously, the wavelength (λ) in metres of the wave is dictated by the frequency |
- | <latex> $$ \lambda = \frac{300}{f} \qquad \text{or} \qquad f = \frac{300}{\lambda}$$ </latex> | + | <WRAP centeralign> |
+ | \$$ \lambda = \frac{300}{f} \qquad \text{or} \qquad f = \frac{300}{\lambda}\$$ | ||
+ | </WRAP> | ||
- | This explains the Band name in the table on the [[intro# | + | This explains the Band name in the table on the [[intro# |
Now it turns out that the size of the antenna is very closely related to the wavelength of the signal we wish to transmit or receive. | Now it turns out that the size of the antenna is very closely related to the wavelength of the signal we wish to transmit or receive. | ||
+ | |||
+ | We say " | ||
===== Cellphone Antenna ===== | ===== Cellphone Antenna ===== | ||
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====== Questions ====== | ====== Questions ====== | ||
- | [[sections | + | [[empos |{{/ |
howto/hambasics/sections/polarization.txt · Last modified: 2020/11/08 16:10 by va7fi