As soon as you look deeper into FPV flying, you will realize not only there are many brands of equipment you can choose from, there are also a range of different FPV radio frequencies available.
Radio Frequencies for FPV
Usually people decide on what frequency they want to use before picking a brand/model of FPV system, since some of the brands specialize / only produce equipment for certain frequencies.
Usually these frequencies are available for FPV system equipment.
- 900 MHz
- 1.2 GHz
- 1.3 GHz
- 2.4 GHz
- 3.3 GHz
- 5.8 GHz
Difference in FPV Frequency
Generally, you want to go lower in FPV frequency, because the lower the frequency band, the longer the waveform is produced. The longer the wavelength, the better it can get around or penetrate objects such as hills, buildings and trees (see penetration depth VS frequency), so the longer distance the signal can travel in our flying environment.
Unfortunately, not all frequency bands are legal, and there are restrictions on certain frequencies in some countries. Do find out about what frequencies are legal to use in the country you are planning to fly FPV, before buying the equipment. In this article, I will use the UK as an example.
In theory 900MHz should give you brilliant range and penetration. But it’s the least used frequency band for FPV due to the fact that the antenna is huge, and not many manufacturers make them currently.
This would have been the most obvious choice for FPV, but the UK government started using this frequency for mobile 3G network in 2009, so it’s no longer legal to use for RC hobbyists.
This band provides great range and good penetration ability, however the antenna is huge. You might also run into trouble pairing this to your 2.4Ghz radio transmitter as they sometimes interfere with each other. Hobbyists sometimes use low pass filters to solve this problem.
But again it’s illegal for use for FPV in the UK.
Similarly good range and penetration ability to the 1.2 GHz band. People in America use this frequency band for transmitting video/audio if they have a Amateur Television or ATV license from a ground based station. For the UK at the moment it is used for aerial work, so it’s again illegal in the UK.
You can get a good range out of this frequency band, and it has a very good range to power ratio. It was much more popular back in the days with 27mhz, 72mhz and 433mhz radios, when it didn’t interfere with each other. Less so now as we FPV hobbyists mostly use 2.4GHz for radio control.
The penetration ability is not as good as the previous frequency band. Also given the fact that it’s the most used band for many other equipment such as WiFi, Bluetooth, RC transmitters/receivers, you might get into some serious interference issues. So usually if you decide to go with this band for FPV, you need to choose a different frequency for your RC transmitter other than 2.4GHz.
3.3GHz is a relatively new frequency used for FPV. It’s potentially a good alternative to 1.2GHz and 5.8Ghz, as it offers greater range than 5.8Ghz yet antennas are relatively small. It also doesn’t interfere with 2.4Ghz radio link. However, it is 3.3GHz is illegal to use in many countries for FPV, so check before using it.
5.8 GHz is probably the most popular frequency band among all, due to the fact that the antenna can be made very small because of the higher frequency. Equipment is also being made cheaper and cheaper because of the higher demand. Finally it also doesn’t affect 2.4GHz radio control link, making it a great companion frequency.
Although it has got a decent range to power ratio, again due to the high frequency it has a very poor penetration property. Therefore flying is restricted within line of sight area mostly for med/long range flying.
Legal FPV Frequency and Power Level In The UK
Not only are there certain frequencies that are legal for FPV flying but there are also constraints on the video transmission power levels as well. For more detail check out this PDF.
So we know we can only use 2.4Ghz and 5.8 Ghz frequency bands for FPV in the UK, we will have a look at these for their max legal transmission power level.
For 2.4Ghz, the max power is 10mW. For 5.8Ghz the max power allowed is 25mW. (information from here)
Conclusion – What Frequency Should We Use for FPV?
In the case of flying FPV legally in the UK, not fun at all. Most decent FPV equipment are baiscally illegal to run due to the transmission power restrictions. However if we are only talking about frequency, the most popular choice is using 2.4 GHz for Radio control and 5.8 GHz for FPV, for the reason of being legal and the cheapest option.
Some people have also suggested using the 35MHz for radio control, which gives us excellent range and faultless results for control, as the 35 MHz doesn’t affect the video signal at all. And use the 2.4 GHz for FPV, which keeps us all legal and have good video quality.
I have also seen people flying FPV with illegal frequency and transmission power level, A LOT, without getting caught. When you are flying in a remote site, I seriously doubt anyone would notice you are there using a illegal frequency band, unless you annoy someone by affecting their activity. Of course, you should always follow the law, and don’t do anything stupid. :-D
There are also things to consider when choosing frequency for your FPV system due to the fact that harmonic frequencies can cause interference, for example 2.4GHz might interfere with 5.8GHz. But from experience it doesn’t seem to be too much of a problem for me and other people I know, so I won’t talked about this in this article.