howto:hambasics:sections:polarization
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howto:hambasics:polarization [2019/11/26 07:06] – [Wavelength and Antenna Length] ve7hzf | howto:hambasics:sections:polarization [2020/11/08 16:10] (current) – 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. | ||
+ | <WRAP centeralign> | ||
{{dipole.gif}}{{radiationpatternh.jpg}} | {{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 ====== | ||
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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 |
+ | |||
+ | <WRAP centeralign> | ||
+ | \$$ \lambda = \frac{300}{f} \qquad \text{or} \qquad f = \frac{300}{\lambda}\$$ | ||
+ | </ | ||
- | < | + | This explains the Band name in the table on the [[intro# |
- | This explains | + | 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. For a dipole, the total length is roughly half of the wavelength. So an antenna for the 2m band should be roughly 1m long, while an antenna for the 160m band would be roughly 80m long! |
- | 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.1574780799.txt.gz · Last modified: 2019/11/26 07:06 by ve7hzf