= Propagation =

Radio Propagation is how signals from the antenna move through space.

Some notes

* VHF/UHF can be absorbed by leaves, so they travel farther during winter
* Fog and rain absorb UHF

* VHF/UHF can interfere with each other, leading to dead spots and blending.
  When moving this can happen quickly (as dead spots are ~1/2 a wavelength
  apart) and cause a fluttering

== Ionoshpere ==

The ionosphere is a region 30-260 miles above the earth that contains charged
O2 and N2 (from being bombed with UV, they are conductive).

=== Layers ===

The Ionosphere has layers that can reflect different wavelengths. Usually more
reflection is done at night, as the sun charges the particles and allows them
to bounce the signals. Sun spots also increase this activitity.

Below are the list of layers

| Layer | Altitude | Notes |
----------------------------
| D  | 30-60 mi  | Often absorbs most signals      |
| E  | 60-70 mi  | Reflects VHF/UHF, up to 1200 mi |
| F1 | 70-140 mi | Only exists during the day      |
| F2 | 140+ mi   | Combines with F1 at night       |

Note

* E skip of E,,s,, happens most duirng early summer and mid winter 
  - 10, 6, and 2 meters only
  - This is what makes HF so good at long distance comms
* F1 and F2 combine at night, due to not being as charged

Different parts of the ionosphere are charged at different times of the day,
making it so comms one way but not another are possible, and making it so that
ability to talk is limited by seasons, weather, and the sun cycle.