What are the frequencies used for within drones?

Question

What are these frequencies used for within the drone technology, and why these values?

• 35 MHz
• 433 MHz
• 868 MHz
• 2.4 GHz
• 5.8 GHz

Answer 1

Spectrum licensing

There are only a limited number of frequencies in unlicensed bands which can be used for radio control, and different countries have different licensed bands for different uses.

For instance:

• 35MHz is available for RC use in many countries in Europe, but other countries use a whole variety of other frequencies below 100MHz.

  • I found a wealth of information on this at the UK Radio Control Council website.

• 433MHz is in the ISM Band in Region 1

  • That's the "industrial, scientific and medical radio bands" for use in "Europe, Africa, the Middle East west of the Persian Gulf including Iraq, the former Soviet Union and Mongolia".

• 868MHz is allowed for "Non-Specific Short Range Devices in Europe" within certain limits.

• Finally, both 2.4GHz and 5.8GHz are ISM Bands with worldwide availability.

I found much of this information in the ISM-Band and Short Range Device Regulatory Compliance Overview document from Texas Instruments.

Frequency characteristics

In terms of actual use, different frequencies have different advantages and disadvantages. So in general:

• Lower frequencies require a larger antenna and generally have a lower data rate, but require less power and have fewer line of sight issues.

• Higher frequencies have more bandwidth available, so you can get more/wider channels and a higher data rate (see the Shannon Hartley theorem) and you can can use smaller antenna, but line of sight starts to become a major issue, and you need more power for the same range.