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The custom.css changes have changed the behaviour of list items, removing the top & bottom margins, so hopefully looking more like a list and less like a group of items spread across the page.
29 lines
2.6 KiB
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29 lines
2.6 KiB
Plaintext
---
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id: non-aerial
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title: Non-aerial factors affecting transmission
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sidebar_label: Non-aerial factors
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slug: /hardware/non-aerial
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sidebar_position: 2
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---
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Unless you're using your devices in a vacuum, with clear line of sight between aerials the following will have an effect:
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- Weather (temperature, humidity, and air pressure),
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- Transmission power, bandwidth, spreading factor, and other associated channel factors,
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- Number of nodes within reach of the mesh (affects retries consequent duty cycle hit),
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- Absorption by materials (with varying degrees attenuation, by material and depth),
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- Reflection off surfaces (and channeling through material tunnels, including warm / cold air tunnels commonly present in the atmosphere),
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- Diffraction around obstacles (over forests and around corners).
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- [Fresnel Zone](They may not have been selected for your given frequency range, tuned or of a quality design.) - Football shape between antennas that must be clear of obstructions or else the signal is attenuated.
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### Environmental factors
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For a bit of light reading on environmental research:
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- [RF attenuation in vegetation](https://web.archive.org/web/20201216041455/https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.833-9-201609-I!!PDF-E.pdf) (yes really); if you wander through the woods wondering how your RF is bouncing off leaves dependent on their variety, and wind speed … well you do, now.
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- [RF attenuation with various building materials](https://www.ofcom.org.uk/__data/assets/pdf_file/0016/84022/building_materials_and_propagation.pdf).
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- This one by ITU again is very detailed in its [analysis of the drivers of attenuation](https://web.archive.org/web/20211005174833/https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.2040-1-201507-I!!PDF-E.pdf) (I wasn’t aware that all EMF radiation exhibits reflection / transmission characteristics akin to light hitting a material boundary. So, depending on the angle of incidence, material and the EMF wavelength, it will be reflected and / or transmitted through).
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- These RF bands are also made more [noisy by adjacent LTE](https://www.ofcom.org.uk/__data/assets/pdf_file/0023/55922/lte-coexistence.pdf)
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In summary - wavelengths in Europe fair well in plain sight, curve over not-so-tall obstacles (including trees), and they reflect off surfaces at low angles of incidence. They go through humans without much attenuation; but not brick, stone, or anything with more attenuation than glass / Kevlar. Oh, and don’t sit under an LTE tower and expect it to be plain sailing. RF emissions at adjacent frequencies can interfere at a high enough power.
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