Like engines, there are all types of radio control units with a huge variety of features and gadgets. The most common names you will come across in Australia will be JR (Japan Radio), Futaba, Hitec, Spektrum, Jetti, Turnigy, FRSky. The JR and Futaba sets have been around forever and are reputed to be the better of the brands but you will pay more for them, the others are quite okay too. Most radios sold these day operate on 2.4gHz and require no frequency control. There are still a few people still flying on the older frequencies of 36mHz and 29mHz. If you plan to use the 29mHz or 36mHz there are very strict frequency controls in place so you do not clash with others on the same band and you should familiarise yourself with them before turning on the radio near any other flyer.
It is not recommend to fly any model on 27mHz as this is the CB radio frequency and is subject to interference. Some toy shops sell radio control toys on 40mHz, these toys usually have a very limited range.
A complete radio set consists of the transmitter, the receiver, servos, switch and battery packs. Not all radio sets come with batteries, these are called DRY sets. Manufacturers sometimes do a crazy thing by giving you one less servo then you need. Basically speaking, all the servos and the battery pack plug into the receiver via the switch and are mounted in the model. The transmitter stays on the ground with you and transmits the inputs you give it to the receiver, these are fed to the servos which are connected to the control surfaces of the aircraft.
One question that everyone asks is how far will the signal go before transmitter won't talk to the receiver. Well, the answer is 'out of sight'… about one kilometre. You will lose sight of the model before it loses signal, obviously if you can't see the model you can't control it so it flies directly to the crash site.
You will hear people talk about the number of channels a radio has. Each channel is used to control one function on the plane. In aero modelling most radios control the four major flight controls… Elevator, Aileron, Rudder and Throttle, so you need a minimum of a four channel radio for the standard plane. If you want to control things like Flaps, Retractable Wheels, Bomb Doors, Smoke etc you need an additional channel for each feature. Obviously the more channels you have the more expensive the set.
In the main, radios can be divided into two categories, Computerised and Non-Computerised. With technology becoming so affordable nowadays computerised radios are more common. Many of the smaller radios (2 channels) are not computerised and are used in models like gliders, cars boats etc.
So what's the big deal with a computerised radio ? They allow you to electronically adjust many different behavioural aspects of the servos and hence the controls of your plane. For example, if the controls are too sensitive and your plane is ducking and diving around the sky you can simply go into the menu and back off the 'travel rate' of the servos, or, after you have installed the radio in your model you find one of the controls are back to front, simply go into the menu and reverse the throw on that servo. These are just a couple of the basic things you can do, they do more complicated stuff which I will not go into here.
Be very careful when buying radio systems from overseas. The U.K. and Europe for instance have very strict controls on how much power (signal) a radio can put out and their radio systems actually put out HALF the signal as the Australian radios. There are other countries in the world that that have the same regulations.
There are two modes that you will commonly come across, Mode 1 and Mode 2. The difference between the two is that the controls are in different positions. Mode 1 has the throttle and aileron on the right hand stick and the elevator and rudder on the left hand stick. Mode 2 has the elevator and aileron on the right hand stick and the throttle and rudder on the left hand stick. You can see that they do not simply have the sticks crossed over but the controls are also mixed up a bit. So the $64,000 question is... which is better ? This the source of many an argument at any flying field and always will be. Basically it boils down to what mode your radio is on when you buy it and what mode the person who is going to teach you to fly is on. About 70% to 80% of Australian flyers are on Mode 1. It is almost the opposite in the U.S.A. Many people in the UK are on Mode 1 but most people in Europe are on mode 2. Personally, I recommend people go mode 1 (You can see I'm a mode one flyer) because with more people being on that mode in Australia the more chance you have of getting someone to teach you. Also if your instructor is not at the field the day you want to have a fly there is more chance of finding another mode 1 flyer to help you for that day. Now that statement is grounds for a real argument at any field but it seems to make sense to me.
It is now a requirement to ‘Range Test’ our models before the first flight of the day. We do this to ensure the transmitter is putting out a good signal to the receiver in the model.
Most radios have a button on them that you hold to perform the test, some radios you have to go into the menu and turn Range Test on. Putting the radio into range test mode reduces the output power of the transmitter down to below half power.
To complete a range test... secure your model, turn on the transmitter first then turn on the model. If you have a glow or petrol engine it is recommended you complete the range test with the engine running. Hold the range test button, or switch to range test in the menu, and walk about from the model. As you are walking away (still holding the range test button) move the controls on the radio and make sure the model is responding accordingly. You need to be able to get at least 30 metres from the model and still be able to operate all the controls on the model. If the controls start to jitter then there is a problem and you should not fly until you have sorted it out.
Buddy Box System
This is where both the instructor and the student have a transmitter and they are connected by a cable. The instructor has the master radio and the student has the slave. The instructor holds up a switch to give control to the student, if the student gets into trouble he just releases the switch and he has control again. A great system but both radios must be from the same manufacturer and you need the cable which comes as an accessory. Usually the basic model radios do not have the plug for the lead.
Okay, What To Buy
Use the old golden rule again… buy as good as you can at the time as your radio will last you for many years and many models to come. You might not use all the features and channels of the radio when you are starting out but you will use most of them later in your hobby career. You should only buy a radio brand that is approved by the Model Aeronautical Association of Australia (MAAA) so you will be covered by their insurance. You will also know that it is a tested and proved system. You can go to their website for the list of approved brands.
Have a chat to whoever is going to teach you to fly and see what they are using. Not only for the prospect of using the buddy box system but they can also help you with the menus and jargon of the radio. Although most radios have the similar features different manufacturers use a different menu structures and terminology.
It’s recommended to use rechargeable batteries in your radio, it will save you a fortune in the long run, many people are using lithium batteries in their transmitters, make sure you use the correct voltage and go for the highest amperage batteries you can afford, the longer the charge lasts the better.
Non computerised radio will be slightly cheaper but not really recommended
Be careful of mixing and matching servos from other manufacturers as the polarity and plugs can be different. The polarity of a JR transmitter charger is opposite to that of a Futaba and Hitec, beware of mixing your chargers.
If you can't afford new certainly look around for a second hand unit. Like everything else, get someone who knows what they are looking at to look over the set BEFORE you pay out your dollars. Check the condition of the batteries, check that the servos don't have any broken gears or mountings. They are the first things to strip in an accident. Be particularly careful that the radio does not have 'Blackwire Syndrome' This is where the black wire (negative) from the battery gets that greeny look to it and eventually flakes away. This will definitely mean a new battery pack and definitely an internal inspection of the radio. Range test it. Beware that some 'helpful' modeller is not trying to unload his junk on to you.
Don't leave your computer radio in direct sun for too long, it can be effected.
Contributed by Brian Carson - SMF Senior Instructor (Note from Bob Cottle - Webmaster)