When you choose your first RC helicopter it will be equipped with a radio transmitter. This will probably be a conventional 72MHz or 35MHz PPM/PCM. However, if you are lucky it might be one of the new 2.4GHz spread spectrum models.
Without going into too much detail, conventional RC electric helicopters operate at a single frequency on a set bandwidth. They might be PPM (Pulse position modulated) or PCM (Pulse Code Modulated, which is slightly better) but it still equates to interference between helicopters flying on the same frequency in groups, and interference from practically anything when flying alone. It’s the reason peg boards are used at group meets.
Recently, a new technology was developed, called spread spectrum modulation. Unlike the PCM/PPM system, in which each of the RC helicopters has its own, single frequency, spread spectrum RCs transmit over a large range of channels within the 2.4GHz bandwidth, simultaneously.
This sounds like a confusing mess. It might be confusing, but it isn’t a mess. As well as making crystals and peg-boards a thing of the past, it also eliminates most of the interference caused by non-RC sources such as mobile phones.
But how does it work? Well, when SSM radio control helicopters are built, each transmitter is assigned its own unique code, which is programmed into the receiver. The two lock on to each other when the transmitter is first turned on and from then on the receiver will only respond to the specific set of frequencies being sent by the RC.
Because there are so many frequencies available on the 2.4GHz bandwidth, every RC will have its own unique “set”, encoded on the receiver. It’s unlikely anyone else will be operating at exactly these same frequencies and, even if they were, the chances of you standing next to them would be minute. Each receiver is uniquely encoded anyway, making this point irrelevant.
The upside of all this, is that many spread spectrum RCs can be used together without interference either from each other, or from other radio sources. Because each RC is constantly scanning across the 2.4GHz bandwidth randomly, it means several RC helicopters can fly in tight formation with no chance of frequency interaction.
Another plus, is that the sending and processing of 2.4GHz radio commands are much, much faster. All of which can only be good for the future of RC electric helicopters.