Radiolink T4U -
http://www.radiolink.com.cn/doce/product-detail-42.html -
http://www.giantcod.co.uk/gianitcod-24ghz-4channel-mode2-transmitter-p-403779.htmlWhile looking for cheap imported brushless motors I came across the RadioLink T4U 2.4Ghz radio for sale on the Giant Cod website, who, I think, are the sole UK importer. At a price of £25 it seemed too good to be true, but the comments on the associated forum were uniformly good, and I bought one to see what this new frequency might offer...
What you getThe radio comes as a Tx/Rx combo. Extra receivers are very cheap (£9) and I bought two at the same time, as well as a selection of cheap Giant Cod miniature servos (£1.99 each, though now at £2.23!). All this arrived within a few days in a well-packed parcel.
The TX/Rx combo came in a simple white cardboard box, with no internal packing or advertising material. There were no instructions included, and presentation had obviously been sacrificed with the aim of keeping prices down. This really is a rock-bottom cost unit!
TxFirst impressions of the Transmitter were mixed. The unit is quite large, around 7 1/2" square not counting the aerial, is made of thick black plastic and has a satisfying solid feel. But the trim is cheap aluminium printed strip, with a blanked-off hole for exchangable crystals (not needed on a 2.4Ghz set), and a primitive row of four slots cut in it through which you can use a screwdiver to alter the servo-reversing switches on the internal PCB. The stick gimbals (adjustable length) were of good quality, smooth and strong, and the mechanical trims had a soft, quality feel to them. The On/Off switch cover had come off in the box (easily replaced), and I had to open the Tx case to loosen the aerial screw to allow it to be centered from its sideways transit position.
The system is advertised as a simple 4-channel radio with no features. Apart from the pair of stick gimbals, the front of the radio has a Power switch, a very solid boss for attaching a strap, and a red led light. This glows when power is on, and (according to the forum) blinks when the voltage is low, though I have not tested this.
On the side of the Tx there is a charging socket (no charger is included), and on the back is a 'Trainer' socket (not functional), and a battery cover for 8 AA cells. It will work with Ni-Cad/Ni-Mh or alkalines.
RxThe receiver is a small hard plastic case with a single-deck PCB inside, though this has a daughter board attached to the top to provide an aerial circuit. The Rx is about 1 3/4" x 1" x 1/2", and has outputs for 6 servos, plus another marked '7/Batt'. There is only one aerial, and a single small binding button. The version I have has the connectors mounted vertically in the case - they can also be bought with a horizontal mount varient. Binding is very simple - just turn on the Tx, turn on the Rx and press the Rx button. A green flashing light from the receiver tells you that binding has been successful. The forum warns people that trying to bind close to a computer wireless connection which is also transmitting at 2.4Ghz may cause problems, but I had no difficulty with one about 12 feet away...
OperationI have found the set to be very reliable in practice, and easily equivalent to my other more costly sets. It has no computer set-up or model setting memory, so I suppose it should be compared to the simple 27Mhz systems on sale, though the sophistication of a 2.4Ghz makes for a much easier operating experience, especially at a crowded pool.
Given that there were no instructions of any kind included with the set, I went to the Giant Cod forum to gather more information about it. This produced some surprises.
The first is that the Tx has two undocumented switches on the internal PCB. There is a 'Mode' switch, allowing easy change between Mode 1 and Mode 2. There is also a 'Mixer' switch, which allows channels 1 and 2 (Aileron/Elevator) to be run either seperately or mixed.
The second is that, though the set is advertised as 4-channel, the internal circuitry for 6 channels appears to be included. The Tx PCB has several 'spare' sockets on it which can be used to 'upgrade' the sets (though this service is not offered by the manufacturer). The Giant Cod forum has details of the circuit changes (remove a resistor and attach a switch) to give an extra switched channel, and it seems likely that another proportional channel and the trainer/simulator socket can be made operational.
There is considerable discussion of this set at Giant Cod, including a circuit for multiplexing two of the receivers to provide a high-security redundant radio link for critical applications, and details for adding rate switches to channels. Early versions of the set needed an extra resistor to be added to the sticks to allow full throw, but I understand that this has now been corrected. The 'insides' picture below shows a couple of unconnected components which I am adding to provide rate control...
ConclusionsThe early versions of this set were similar to many Chinese products - inadequately documented and of variable quality. But the current sets seem to be improving, and offer excellent value for money. A manual for the set now seems to be available from here: http://www.radiolink.com.cn/upload/2010/04/08/q3tzer6l1q1n21270694380.pdf
Even so, given the sparse nature of the back-up and information on this set, I would say it was more useful to the experienced modeller who wants a rock-bottom priced intro to 2.4 Ghz rather than a beginner who does not know how to use a radio. But it works well, and the price is hard to beat. I think that this is the cheapest 2.4Ghz set currently available from a UK distributor...
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Topic: Radiolink - T4U Review (Read 22224 times)