The 2.4GHz radio connectivity link has been used for ages for Remote Control toys and other equipment such as drones. The reason for this widespread usage being that 2.4GHz has better bandwidth and frequency allocation to accommodate multiple transmitter and receivers in a vicinity without causing interference to each other and failsafes. 2.4GHz type transmitters provide decent range, a Flysky i6 transmitter provides few hundred meters and the FrSky transmitter can provide around a mile of range. The FrSky R9 Range is much, much more than those 2.4GHz systems, at almost 10KM of range!

In this article, we will see why we might require such a system and what the range of it is like in real world.

What are the key different advantages and disadvantages of 2.4GHz Radio Control systems?

Like mentioned in the introduction, 2.4GHz radio systems provide a lot of bandwidth which is a reuirement to send across more data, but is not the main reason why people have chosen this frequency. 2.4GHz spectrum is considered license-free in most countries across the world and provides good spectral immunity to those devices in use.

During the 90s and the years prior to that, 27MHz and 72MHz systems were more common, and only a few pilots could fly at a single point of time as it would cause interference to the person flying next to them due to the very small frequency separation due to the lack of bandwidth. This is when people decided to  switch over to 2.4GHz radio systems as it allows to have dozens of pilots flying or operating together in close vicinity without causing interferences to the next person.

One of the biggest disadvantage of increasing the frequency is that you lose range of your system and In most cases, you are not going to that great of a range from your stock transmitter module as it can only do upto ~100mW in most cases. This is not much of an issue in close flying or in races but for freestyle pilots or long-range flights, this will be something that holds them back from reaching the full potential of their flight rigs.

How will the 900MHz systems overcome the shortcomings of 2.4G?

The drawbacks of the 2.4GHz system are quite obvious to us now and there is mainly just one issue -  the lack of range! Let us see a bit more in detail on why this is so.

900MHz systems (868/915MHz depending on which country you live) are low-powered long range systems based on LoRa (Long Range) technology and since it uses a lower frequency, it has longer wavelength and this helps the signal to penetrate and move through a lot of objects and buildings and puts out better range at the same power output as a competing 2.4GHz radio system.

The FrSky R9 Range

The FrSky R9 system can do from 25mW to 1W of power. And at 1W of power, you can expect almost 10KM (or even more!)  in light of sight flights, which is amazing!

The range of this system depends vastly on the output power and the antenna orientation along with the environment. Unlike 2.4GHz systems, the 900MHz systems are far more susceptible to range cut off depending on the antenna orientation due to the longer wavelengths. Most fliers receommend keeping both transmitter and receiver antennas perpendicular from the body so the antennas themselves are mostly parallel to each other. Signal transmission is at its peak when antennas are kept parallel to each other.

The R9 system can vary its output power output from 25mW, 100mW, 500mW all the way to 1W of peak power which can be useful in long range and also for short range flying with obstacles as 900MHz systems have more penetratrive power as compared to 2.4GHz at the same output power.

In this article, we have briefly seen the FrSky R9 system and the range it produces compared to other frequencies such as 2.4GHz. The R9 system is FrSky’s long range system that takes on the likes of Team Black Sheeps CrossFire system. The FrSky R9 Range is very much longer than the 2.4GHz FrSky systems we are used to and it opens a new frontier of long range flights when paired with 2.4GHz or even better, 1.3GHz systems.