howto:hambasics:sections:propagation
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howto:hambasics:propagation [2019/11/24 19:15] – [Auroral backscatter] ve7hzf | howto:hambasics:sections:propagation [2021/01/03 08:06] (current) – va7fi | ||
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====== Propagation ====== | ====== Propagation ====== | ||
Radio wave propagation describes the way in which radio waves travel from one point to another. | Radio wave propagation describes the way in which radio waves travel from one point to another. | ||
+ | |||
+ | {{ youtube> | ||
====== Direct Waves (Line Of Sight) ====== | ====== Direct Waves (Line Of Sight) ====== | ||
{{ lineofsight.png? | {{ lineofsight.png? | ||
- | VHF radio waves (above 50 MHz) travel more or less in a straight line, and so cannot go much beyond the horizon. | + | VHF radio waves (above 50 MHz) travel more or less in a straight line, and so cannot go much beyond the horizon. |
- | For example, | + | For example, |
For direct waves to occur, the height of the antenna needs to be many times greater than the wavelength of the radio wave so that the signal doesn' | For direct waves to occur, the height of the antenna needs to be many times greater than the wavelength of the radio wave so that the signal doesn' | ||
Line 115: | Line 117: | ||
+ | ===== Animation ===== | ||
+ | Here's the animation if you want to move the dials and experiment with it yourself. | ||
+ | |||
+ | {{ggb>/ | ||
===== Meteor Scattering ===== | ===== Meteor Scattering ===== | ||
When meteors enter the ionosphere, they create intensely ionized columns of air that can scatter radio waves for very short periods of time (from a fraction of a second to a couple seconds per event). | When meteors enter the ionosphere, they create intensely ionized columns of air that can scatter radio waves for very short periods of time (from a fraction of a second to a couple seconds per event). | ||
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===== Sporadic-E propagation ===== | ===== Sporadic-E propagation ===== | ||
- | Sporadic-E propagation (not to be confused with ordinary E-layer propagation) takes advantage of ionization patches in the E layer that drift westwards at speeds of a few hundreds of kilometres per hour. You can think of it as invisible clouds of ionized gases that move in the layers. If your signal is lucky enough to enter one of these clouds, it can bounce between 1000 and 2000 km in a single hop. Sporadic-E is most often observed on the 6m band. | + | Sporadic-E propagation (not to be confused with ordinary E-layer propagation) takes advantage of ionization patches in the E-layer that drift westwards at speeds of a few hundreds of kilometres per hour. You can think of it as invisible clouds of ionized gases that move in the E-layer. If your signal is lucky enough to enter one of these clouds, it can bounce between 1000 and 2000 km in a single hop. Sporadic-E is most often observed on the 6m band. |
====== Troposphere ====== | ====== Troposphere ====== | ||
- | On the previous | + | In the previous |
- | Here we discuss how the [[wp> | + | Here we discuss how the [[wp> |
+ | ===== Tropospheric Ducting ===== | ||
+ | The index of refraction of air is lower when the air is warmer. | ||
+ | Unlike Ionospheric refraction, Tropospheric ducting is observed at VHF frequencies as opposed to HF frequencies. | ||
+ | ===== Scattering ===== | ||
+ | At VHF frequencies, | ||
- | * Tropospheric bending on 2m | + | Scattering can also allow HF signals from the skipzone to be heard. |
- | * Ducting | + | |
- | * Sporatic E | + | |
- | * Auroral propagation | + | |
- | * Scatter | + | |
- | * Meteor | + | |
- | See [[wp> | ||
+ | ===== References ===== | ||
+ | * [[https:// | ||
+ | * [[http:// | ||
====== Questions ====== | ====== Questions ====== | ||
* B-007-001-001 -> B-007-004-002 | * B-007-001-001 -> B-007-004-002 | ||
- | * B-007-005-001 -> B-007-007-001 | + | * B-007-005-001 -> B-007-008-001 |
+ | * B-007-008-006 -> B-007-008-011 | ||
- | [[sections | + | [[waveinteraction |
howto/hambasics/sections/propagation.1574651705.txt.gz · Last modified: 2019/11/24 19:15 by ve7hzf