eli5: NASA mostly uses UHF antennas for interspace communication, why?
In: Physics
SHF, actually. There are a couple of reasons for this. One, lower frequencies (pretty much anything under 20 MHz) rarely, if ever, make it past the ionosphere (and it takes a ridiculously large amount of power for those low frequencies to do so). The higher the frequency, the of a chance that the ionosphere reflects anything, and the less attenuation (lowering of power) from the atmosphere, overall. Also, the higher the frequency, the smaller the antenna.
There are some downsides, of course, to using higher frequencies. The higher your frequency, the smaller your footprint, or range. UHF and SHF antennas counter this by being directional antennas (usually, depends on the application) that focus all of their energy in a much tighter beam (like an open bulb versus a flashlight). UHF and SHF also don’t like stuff in the way; they don’t diffract or refract very well, which is why your wifi doesn’t like structural walls.
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