Spektrum DSM2 compatible 2.4GHz receiver

In popular modeler shop Hobby City (a.k.a. Hobby King) cheap Spektrum DSM2 compatible 2.4GHz receivers became available recently. These receivers despite relatively low price (about 3 times lower than equivalent original Spektrum receivers) are quite good quality, with the comparable reliability and operating parameters. The main difference you will notice is the finishing and packing. When you buy Spektrum receiver it will come packed with big nice box wit printed detail instruction, and the receiver is wrapped in nice case with all pin identification printed. "Chinese" receivers are sold without the case ("naked" printed circuit board) with no pin identification. The receiver is packed with foil bag. There is no instruction included. 6-channel Rx came with binding plug, 4-channel Rx with 1-inch piece of heat shrink tube.

Here is on the picture showing two Spektrum DSM2 compatible receivers next to the original Spektrum AR6100.

As pins on compatible receivers are not described I have verified, that all connectors are exactly the same as in original Spektrum park flyer receivers. With the circuit board on the bottom like on the picture below pins are identified as follow:

Bottom pin = Power negative (-), Center pin = Power positive (+), Top pin = Signal (~)

Connectors are identified as follow starting from the left:

6-Channel receiver: BATT/BIND, Ch3 (THRO), Ch1 (AILE), Ch2 (ELEV), Ch4 (RUDD), Ch5 (GEAR), Ch6 (AUX1)

4-Channel receiver: BATT/BIND, Ch3 (THRO), Ch1 (AILE), Ch2 (ELEV), Ch4 (RUDD)

Binding procedure for these receivers are the same as for original Spektrum receivers. You will need a binding plug - the same plug is used for binding Spektrum receivers. I found a binding plug included in 6-channel receiver sold by Hobby City, however 4-channel receiver did not come with the binding plug. I have successfully did bind these receivers with Futaba 8US with Spektrum DSM2 Tx module. The process will be the same or similar when binding with other DSM2 compatible transmitters.

1. Start with transmitter and receiver powered off.

2. Connect binding plug to BATT/BIND connector on the receiver (the first connector on the left). The binding plug connects bottom pin (Power negative) with top pin (Signal).

3. Power on the receiver by connecting the battery to any other connectors (channel 1-4 or 1-6). I have used standard 4 cells NiCd receiver battery pack (4.8V) however Hobby City specifies that you can use any power source from 3.5V to 9.6V. When receiver is powered up, the orange LED will blink rapidly.

4. Press and hold binding switch on transmitter module and power on the transmitter. At first the orange LED in the receiver will turn off and then will start blinking at significantly slower rate. after a while the LED will turn off again and then will turn on with steady orange light what means the binding process is finished successfully.

5. Now you can release binding switch on transmitter module. Disconnect power and remove binding plug from the receiver. DSM2 compatible receiver is ready to use.

In the video section there is a short video showing binding 6-channel DSM2 compatible receiver with Futaba 8US with DSM2 Spektrum module.

Finally there is a weight comparison between Spektrum AR6100 and DSM2 compatible receivers from Hobby City.

1. Spektrum AR6100 weights 3.78g. Spektrum specifies the weight less than 3.5g, which is lower than the true weight by 0.28g.

2. 6-Channel DSM2 compatible receiver weights 3.39g. The difference between this receiver and AR6100 is marginal. DSM2 compatible receiver does not have a case and when you put it in a heat shrink wrap the weight will be similar to AR6100. Hobby City specifies the weight of 6-channel DSM2 compatible receiver at 4.4g, which is higher than the true weight by 1g.

3. The lightest of these three is 4-channel DSM2 compatible receiver which weights 2.33g. Attached piece of heat shrink tube weights 0.55g, so if you put it on this receiver it will weight 2.88g. Hobby City specifies the weight of that receiver 2.5g without heat shrink wrap (which is more than true weight by 0.17g), and 2.9g with heat shrink wrap (which is exactly the same as I measured).

Here are pictures of all three receivers on the scale.