Futaba 3GR-FS

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This is a new radio control system from Futaba, for surface use in the UK and where 40mHz is legal. It is a 3-channel system, with full proportional control on Channels One and Two for steering and throttle and the Channel Three is switch operated, i.e., a servo will move on command from one extreme of movement to the other. In many ways it does that (and more) which the successful 40mHz Hitec Ranger 3 system has done for model boats over the last decade or so. It is priced at £129 for the Tx and Rx without servos or battery packs and £109 if you want a Xtal controlled receiver in lieu of the synthesizer version. The latter option would rather defeat the object of having the equipment, but the Tx is compatible with existing Futaba 40mHz receivers. It also worked, OK in the workshop, with my existing Multiplex Xtal controlled receivers. It is available from all model shops selling Futaba equipment, which must be the vast majority of them, and it is distributed by Ripmax Ltd. which is the UK importer. Ripmax Ltd. also provides any servicing that maybe required.

The equipment is supplied in the standard type of foam two-part box that is usually enclosed in a colourful outer (black in this case!), Photo 1, which can hold extra servos and chargers etc. depending on the radio set, model and type of equipment.

It is always worth checking that the box has the CE approval logo which means it is legal, Photo 2.

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What do you get for your money?

You get a fully synthesized, with knobs and gizmos, Transmitter (Tx), Photo 3, and Receiver (Rx), Photo 4. ‘Synthesized’ means that there are no Xtals in the Tx or the R303FHS Receiver. The Tx can be set electronically to any of the 40mHz frequencies currently available in the UK and the Receiver can be set manually to any of those as well. You do not receive Tx or Rx NiCad’s, although you do get a Tx that has an internal battery box for eight AA batteries and a four by AA battery box for the receiver together with a switch harness. The transmitter does include a normal Futaba charging socket (centre +ve) which is reverse charge protected. You can therefore install either eight normal single disposable AA batteries, or equivalent rechargeable Nicad or Nimh cells.

Alternatively, it is a simple matter to remove the battery connectors from inside the battery box which is accessed via the usual ‘slide off’ panel on the back of the transmitter and install the standard 8-cell flat pack available from the supplying model shop or generic battery suppliers at trade shows. Rather annoyingly, the connection into the PC board is via a specialised small white two pin style plug and not the standard Futaba servo/battery plug. You can either obtain that plug elsewhere, or fit a Futaba style extension lead socket on the other end of the internal lead, or join your retrofit Tx Nicad directly to that lead. My recommendation is to purchase from someone such as John Poll (Model Power Supplies), Tel: 01827 711501, either a Tx pack suitably fitted with the right plug, or he will manufacture for you a suitable adapter lead. It is best to have the battery removable, since otherwise you cannot ‘cycle’ it to ensure maximum capacity is maintained. This is because the inbuilt circuit board protection means that the Tx battery cannot be discharged through the charging socket. There is plenty of space for the leads to be lost inside the Tx when installing the battery. Anyway, that is the only minor niggle.

The Tx is of a normal size and fits the hands easily. The aerial is relatively short and is not readily detachable. It actually only protrudes from the Tx case some 5cm in the collapsed position. The Rx is tiny and its aerial is barely 45cm long. A bench test with the Tx aerial down and the Rx aerial not stretched out or vertical, but in a wound up ball, had a range of at least 10m (the internal length of my garage and workshop combined. From my experience, this is a good sign of range capability, although it is a bit of an amateurish approach to diagnostics!

The Tx and receiver can operate in either PP(M) mode or HRS (High Response System). The latter requires the Rx to be run on 6v and preferably with digital servos. For our purposes the PP(M) mode is perfectly adequate. On the front of the Tx are four white buttons, ‘SEL’, ‘CH’, ‘+’ and ‘-‘. These buttons are used for scrolling through the various functions on the screen and selecting the preferred option. The R303FHS Rx has three sockets for channels One to Three and another for the battery. As I said before, the aerial is short but then it would be for cars, where a range of 100m (approximately 330 feet) would be more than adequate and probably so for boats as well. The principal advantage that the receiver has is that the setting of its frequency is mechanical rather than the electronic searching used by the Multiplex versions. All you have to do is set the two dials to the frequency you require. If the Tx frequency is 40775, then the two dials which are numbered 0-9 are set ‘7’ and ‘7’ which corresponds to 40-‘77’-5 and that is it. The Tx, rather conveniently when first switched on, gives you its current broadcasting frequency which makes life easier. However the receiver does have to be accessible for frequency change and the digits on the dials are quite hard to read in sunlight.

The Transmitter

For your money you get a ten model memory, two function groups, EPA (servo endpoint adjustment), brake mixing, steering dual rate, ABS, throttle acceleration, steering speed, timer, digital trims, servo reversing, function select lever function, function select switch function, a combination of two rates in specific functions, on/off light intensity, low battery warning and stick length adjustment.

Obviously some of these are of no relevance to a model boat and in particular a scale craft. Examples of how these options can appear on the screen are in Photos 5, 6 and 7.

Practically, the most useful features and not necessarily in order of importance are that you can easily alter the EPA’s of each servo, i.e., the travel of the servo arm in both directions either side of neutral. All channels can have the direction of travel altered at the Tx and the neutral points can be adjusted very finely and the Tx will remember the new settings.

The digital trims, Photo 8, are very precise. On the steering stick as in this photo the horizontal trim (DT-1) is the digital trim and the trim to the left of the stick (DT-3) has another function depending on how you programme the Tx functions. The same applies to the L.H. stick, DT-2 and DT-4. Both of the sticks as fitted are single axis, although the Tx case is clearly designed for dual axis sticks.

The rate of the steering servo can be adjusted and the SW1 switch (top right on the Tx front face) is used to change the rate. This means that you could have 100% of servo movement for setting A, but only 60% for setting B, although you would still use the control stick in the same way. The timer can be useful for timing battery discharge with fast-electric models in races. The steering speed function enables you to slow the reaction of the steering servo to the control signal from the TX. This is useful if you don’t want sharp movements.

You can alter the servo reaction to the command signal from linear to exponential. This means that the servo would move less around the neutral point than at the extremes of travel. In other words you would have more control at low throttle speeds if you wished.

The Tx can remember 10 different models with three digit codes. I would prefer to see the facility to record a recognisable model name such as ‘Scout’ or ‘HMS M15’. There is no facility to alter the stick tension at all, as far as I could see. There is some resistance to stick movements, but not a lot. Both sticks can have their lengths altered +8mm or so. Photo 9 is a side view of the Tx with the sticks fully extended. It is possible to fit longer knobs with the requisite threads from other brands of equipment.

In Conclusion

The set is easy to use, it does what most of us want from a 2/3 channel system and it has the benefit of no Xtals. Price wise it is dearer than ‘standard’ sets, but cheaper (even if you buy the Tx Nicad pack) than 6/7 channel synthesizer sets. Mind you, you would expect that wouldn’t you? Perhaps most importantly, you need never buy Xtals again or wait at the lakeside needlessly, if you want to get operational.