Advantages: the 2.4 GHz transmitters (Tx) and receivers (Rx) feature technology which implies that the peg-board is heading for extinction! Everyone on 2.4GHz can operate at the pond, safe in knowledge that they will not interfere with other users, and vice-versa. Because the radio frequency is so high, you do not need a long aerial. The aerial on the transmitter is so short (a few inches) that aerial protectors are really not needed (and there is a motion at the next club AGM to confirm that). The receiver aerial(s) are exceedingly short (about an inch, although it may have a few inches lead to separate it from the receiver. In my experience, despite the aerials being down inside the hull, reception is good... so there is no longer a need to try and hide a receiver aerial in the boat's rigging. Reception has been solid even for my NQD speedboat which throws up a good "rooster tail" which could interfere with radio reception. The photo (left) shows a SPEkTRUM DX6i Tx, an AR500 5 channel Rx, and a UK pound coin (diameter about 20mm or 0.9").

Disadvantages: there are (at least) two different implementations of 2.4GHz technology. That used by Futaba, "Frequency Hopping Spread Spectrum" (trade name: FASST), continually switches frequencies within the 2.4 GHz band. That used by SPEkTRUM, "Direct Sequence Spread Spectrum" (trade name: DSM2), uses a wide frequency band with encoded information. OK, so you can ignore all of that, but what you do need to know is that the two systems are incompatible. However, since both are designed for "beyond the limits of sight" model aircraft use, they should be easily OK for model boats on Setley Pond! Just realise that you can't mix the two makes and expect them to work; they won't! ..so you have to choose which 2.4GHz system to use.

So how to choose between the implementations? To be honest, when I decided to switch, I didn't do a whole lot of research but simply went for the cheapest receiver, which seemed to be the SPEkTRUM system. After all, you only need one transmitter, but you need receivers for each of your models. Present (Feb, 2009) cost for a SPEkTRUM AR500 Rx from Howes Models is £37 as against a Futaba F617FS for £75. The Futaba systems might indeed have other advantages, but I just went on cost. Multiply the difference in price by the number of models and I decided that I had really no choice.

What did I do wrong? Since I enjoy looking around the Howes store I drove up there, rather than ordering over the internet. However, being headstrong, I ignored the advice of the guy in the Howes store, who races model yachts, knew what he was talking about, and who suggested the SPEkTRUM DX6i Tx. I bought the SPEkTRUM DX5e which came with an AR500 receiver for (at that time, late 2008) £65, i.e. transmitter cost less than £30; really good value. However...

So what were the problems? You have to "bind" each receiver to the transmitter by inserting a special plug in the battery socket of the receiver. This enables the receiver to obey your transmitter, but also it sets the "failsafe" settings for the receiver. In theory, if you have a different receiver in each model, you only have to do this once for each of the receivers. What worried me was that, with the DX5e, there seemed to be no easy way of knowing the setting of the servo trims. They are not sliders, but digital "click" switches. As far as I could see, the only way to know how they are set is to go right to one end of the scale and count the clicks back. If you swap from one model to another and don't get the servo trims set correctly then your "neutral" positions will not be neutral! To get around that, each time I swapped models, I rebound the new model to the transmitter, but that meant accessing the receiver and inserting the rather fragile "bind plug", a couple of which I broke in removing them from the receiver. Some time later, club member Chris Chattaway pointed out to me that the servo trims emit a long tone at their central position. This had been missed by me, and at least one other club member. Thus setting up the DX5e is easier than I initially thought.

I also later realised that, using the DX5e, the best thing would be to put an extension lead on the "battery/bind" socket with a conveniently positioned switch on the end so that you could switch on the "bind" function whenever needed. When "on" the switch just needs to connect the "signal" wire to the "negative" wire to put the Rx in "bind" mode. You can provide power to the AR500 receiver by connecting the battery to any of its other 5 channels, so unless you need more than 4 chanels, this would be a practical solution. You would also need a look-up chart for the servo normal/reverse settings... but that's similar to using MHz band Tx's with multiple models, and you could also note down the servo trim settings. So if you only want to use one or two models, the DX5e is probably a good choice.

So what did I do? Partly driven by my own misunderstandings, I bought a Spektrum DX6i from Sussex models who were advertising the Tx only for £66 (inc. p&p); normally it comes packaged with a 6 channel receiver at greater cost. The DX6i has a LCD panel and a 10 model memory. Programming the settings for different models is via a roller (to the right of the LCD screen in the picture, above) which you rotate to choose an option and then press to select it. This is a very simple and intuitive system (as long as you ignore the 140 page manual which guides you through setting up your Mustang fighter aircraft, or Lynx helicopter for acrobatics!). Since the trim settings and servo normal/reverse settings are remembered by the unit, switching from one model to another only requires you to select the correct model on the Tx screen via a model name of up to 8 characters (which again is quick and easy to initially program in via the roller). During "binding", the receiver learnt it's "model identification" so if you select the wrong model on the Tx... nothing will happen! You won't be using the wrong settings.