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I am designing an autonomous glider. I am also adding a provision to manual override the glider. I want to understand which frequency would be perfect for RF module or transmitters and receivers, so that I can send control signals to the glider. Please do consider the USA regulations by FCC and help me.

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    $\begingroup$ What range do you want to have? $\endgroup$
    – Jacob B
    Aug 14 '21 at 15:04
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There are many different currently leading control frequencies, and you can also deviate from these and design your own radios if you'd like to pull specific advantages/disadvantages

2.4 GHz

Advantages

  • Higher frequency generally means lower latency link
  • More bandwidth allows for faster data rates
  • More bands means more pilots can fly without interference (hundreds at least)
  • Widespread support (spektrum, frsky, eLRS, futaba, hitec, and hundreds more)
  • Small, compact antennas

Disadvantages

  • Shortest range, the higher the frequency, the lower penetration through free space and also through objects
  • Generally plug-and-play (iPhone style) other than expressLRS and openSky (and maybe others). Most of these systems are black-boxes
  • Noisy channels (everyone uses 2.4GHz)

900MHz

Advantages

  • Longer range, better penetration
  • Still good support (CRSF, eLRS, R9, etc)
  • Perfectly acceptable packet rates, even for freestyle/racing quads
  • Outside of the common 2.4GHz wi-fi link, so less noise floor (please don't fly over houses)

Disadvantages

  • Longer, heavier antennas
  • More sensitive to antenna placement (though this is the case with any long range)
  • Smaller bandwidth means a limit may be reached

433MHz

Very similar to 900MHz, however more range, bigger antennas, and less common support.

72MHz

A relic, antennas are so obstructively large that it is annoying to construct 1/4-wave antennas on groundstation or in the air. Easy to transmit on and low noise floor, and most transmitters require very little power due to the impressive penetration. May require customization for long range, however. Low data rates.

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    $\begingroup$ A half-wave dipole for 72 MHz is two meters long. For a large glider, a pair of dipoles wouldn't be a problem (one along the fuselage, one across the wings). The transmitting antenna would still be a pain, though. $\endgroup$
    – Mark
    Sep 1 '21 at 19:57
  • $\begingroup$ Fair enough - I generally canned the low-freq FM bands as unbuildable with 27-43MHz in mind, 72MHz is more in the "usable" realm $\endgroup$ Sep 1 '21 at 20:00

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