Introduction

OFCOM is the independent regulator in the UK for the communications industry. In December 2006, OFCOM passed the necessary legislation and gave the necessary permissions for radio control equipment to be sold and used in the UK on the 2.4 GHz frequency band.
Until that date it was only legal to operate model aircraft in the UK on the 27 MHz and 35 MHz bands. These bands remain legal for model aircraft flying.
The first 2.4 GHz radio gear to hit the modelling market was introduced by Horizon Hobby in late 2004, consisting of add-on transmitter modules and matching receivers for model cars. These early systems were released under the Spektrum brand. Early aircraft radios on 2.4 GHz were limited to only 6 functions; more than enough for most aeroplane fliers but rather limiting for glider and helicopter enthusiasts. Spektrum later released a 7 function aircraft system in 2006. The Spektrum systems are certified for use in the EU and UK.
JR later joined the arena, having unique access to the Spektrum technology through Horizon Hobby. JR actually manufactures the Spektrum radio equipment under licence. Currently JR has 9 and 12 function systems on release in other countries but they are not yet on release in the UK and are not certified for use in the EU or UK.
Futaba has been manufacturing 2.4 GHz radio systems in industrial machinery for over 15 years and they wasted little time in introducing rival systems to the Spektrum and JR gear. Futaba gear does not utilise Spektrum technology. Currently Futaba has a 6 channel system on release in the UK with 7 and 12 channel systems on release in other countries.
Please note: Be wary about trying to import 2.4 GHz systems from other countries. Not all systems are certified for use in the UK. You must check that the gear you are importing has been tested and certified for EU and UK use. As an example, JR's X9303 is legal for use in the USA but the EU requires a much lower transmitter output than the USA and the X9303 is not EU certified. It is therefore illegal to operate it in the UK and you would also invalidate your insurance by operating it.

What's all the fuss about?

The 2.4 GHz frequency band has been used for several years by the computer and telephone industries to reduce interference, increase signal resolution and strengthen the links between transmitters and receivers.
Similar technology has been brought to model radio control systems meaning that radios operating on the 2.4GHz band have several key benefits that will almost certainly see them render 27 MHz and 35 MHz systems obsolete over the course of the next decade:

1. Current 27 MHz and 35 MHz radio systems require active frequency control by the operators. At club level, this is usually in the form of a peg-board where you either attach a peg to the board (peg on) or remove a peg from the board (peg off) to reserve a radio frequency (or channel) to fly on. This system works well enough but is only as reliable as the people using it. It is very easy for someone to switch a transmitter on when someone is already flying on that frequency with a resultant loss of control of the model, often termed as being 'shot down.' 2.4 GHz systems solve this problem, as the laws governing these devices require them to automatically scan the radio band for free and used frequencies before ever broadcasting a signal. Once they have located a free frequency, they can start broadcasting on it. If there are no free frequencies, they do not start broadcasting. Any 2.4 GHz transmitters switched on afterwards perform the same scan, only ever locking onto free frequencies. It is not difficult to see that this feature alone will convert many modellers to 2.4 GHz radio control systems, as the risk of being 'shot down' will be almost completely eliminated. While 2.4 GHz systems give the benefit of automatic frequency control, the BMFA recommends that clubs operating a peg-on system have a separate area of the peg board for 2.4 GHz users and that they use named pegs. It is also recommended that 2.4 GHz users display a black ribbon on their transmitters. However, a 2.4 GHz user will never have to share a frequency or wait for a frequency to become available and will never have to ask the question, "What channel are you on?"
2. There is no evidence to suggest that 2.4 GHz systems interfere with 27 MHz or 35 MHz systems. In theory it is possible to fly many models at the same time but there have to be sensible and practical limits and flyers should obey their club's rules. Theoretically there are 80 channels available on the 2.4 GHz band. With the Spektrum full range gear this is reduced to 40 channels, because each model has two receivers (see below for explanation).
3. It is worth bearing in mind that 27 MHz gear is legal for use in ground based models as well as aircraft. This means that an aircraft flying on 27 MHz could be 'shot down' by anyone in the immediate area operating a model car or boat on the same channel. 2.4 GHz gear is also legal for land based vehicles, but the automatic frequency control features apply equally to such systems and so the possibility of a model car operator accidentally causing a model aeroplane to crash is also eliminated.
4. Many modellers talk of metal to metal contact causing interference with current radio control systems. This is a product of engine vibration causing metal parts to make and break contact at a frequency relatively close to that used by 27 MHz and 35 MHz control systems. Similarly, interference from electric motor speed controllers and petrol engine ignition systems tends to be relatively close to the old frequency bands. However, 2.4 GHz signals are much higher in the frequency range than most of the typical interference experienced by model radio control systems and so the 2.4 GHz signal tends to suffer less interference than 27 MHz or 35 MHz.
5. Each manufacturer of 2.4 GHz radio gear claims a much faster response time from moving a control stick to seeing a response in the model.

There are further benefits available with 2.4 GHz systems, but not all manufacturers offer the same feature sets.

The Spektrum gear offers the following benefits:

1. The main receiver works in conjunction with a second receiver to form a more robust radio link. The two receivers mean that the radio system is locked onto two channels and can compare the two signals to ensure a very strong radio link. There is also the option to plug in several more receivers to seriously boost the signal clarity.
2. The model memory can be bound to its model so that you cannot accidentally take off having selected the wrong model memory.
3. If you are operating multiple functions off one control e.g. eCCPM helicopters, the system gives each function an instruction at the same time rather than in sequence. This gives a more synchronised control system and in theory should reduce unwanted control crossover i.e. unwanted cyclic commands when giving collective commands and vice versa.

It should be noted that these features are patent protected and other manufacturers may not be able to implement such features.

Futaba has taken a different route with its gear with the following features:

1. Rather than locking onto two frequencies permanently, as the Spektrum gear does, Futaba's 'FASST' radio utilises a frequency switching system that changes the frequency every 2 milliseconds. The theory behind this is that if there is interference somewhere in the 2.4 GHz band, the radio system will only experience it for 2 milliseconds before switching to an unaffected frequency.
2. Futaba's 2.4 GHz receiver uses two antennae rather than two receivers and compares the signals from each to get the best reception. Using only one receiver makes installation easier in smaller models.

Can different manufacturers gear be used together?

There have been few reports of any interference between different makes of 2.4 GHz radio control equipment. The gear has been around for a couple of years and many fliers around the world have flown different brands of gear at the same time without incident.
As long as the radio gear that you are using is tested and certified for use in the EU and UK there should not be any problems.

Further information

If you would like to read more about 2.4 GHz radio systems, please follow these links:

www.bmfa.org/publications/24ghzguidance.html
www.spektrumrc.com/DSM/FAQ.aspx
2.4gigahertz.com/faq/fasst-faq.html