2021-11-11 21:30:01 +00:00
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= Propagation =
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Radio Propagation is how signals from the antenna move through space.
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Some notes
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* VHF/UHF can be absorbed by leaves, so they travel farther during winter
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* Fog and rain absorb UHF
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* VHF/UHF can interfere with each other, leading to dead spots and blending.
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When moving this can happen quickly (as dead spots are ~1/2 a wavelength
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apart) and cause a fluttering
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== Ionoshpere ==
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The ionosphere is a region 30-260 miles above the earth that contains charged
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O2 and N2 (from being bombed with UV, they are conductive).
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=== Layers ===
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The Ionosphere has layers that can reflect different wavelengths. Usually more
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reflection is done at night, as the sun charges the particles and allows them
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to bounce the signals. Sun spots also increase this activitity.
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Below are the list of layers
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| Layer | Altitude | Notes |
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| D | 30-60 mi | Often absorbs most signals |
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| E | 60-70 mi | Reflects VHF/UHF, up to 1200 mi |
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| F1 | 70-140 mi | Only exists during the day |
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| F2 | 140+ mi | Combines with F1 at night |
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Note
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* E skip of E,,s,, happens most duirng early summer and mid winter
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- 10, 6, and 2 meters only
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- This is what makes HF so good at long distance comms
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2021-11-11 21:45:01 +00:00
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* F1 and F2 combine at night, due to not being as charged
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Different parts of the ionosphere are charged at different times of the day,
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making it so comms one way but not another are possible, and making it so that
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ability to talk is limited by seasons, weather, and the sun cycle.
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