Buddying incompatible radios for training?


When I came into R/C aircraft, just like lots of others I joined a club, and was offered lots of good advice, but, due to lack of understanding I’ve made some costly 'newby' mistakes. "Get yourself a transmitter with a least six channels, this will see you through for years to come” was the advice. So off I went to the model shop coming out with a Hitec Aurora 9 after being impressed with all the bells and whistles. This was mistake number one. 

I got back to the club only to discover that the Aurora 9 won't buddy up to a Futaba transmitter – they did tell me but I didn’t understand, I thought I did and assumed that buddy connections were standardised. I hadn’t told the shopkeeper I wanted to buddy up either.

Not a problem, I can fix this I thought, “I’ll buy a really cheap transmitter of the same make”.  I did a little research and discovered that the Zebra 4 uses the same size connection. No model shop locally stocks this so I bought online. This was mistake number two. 


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The Zebra 4 arrived with vague instructions but the recommended lead connection was mono for buddy while the Aurora 9 specifically states stereo – I decide not to risk shorting out my expensive transmitter.

To rectify matters, I bought a Futaba 6EXP with receiver along with a Futaba Skysport 4, just as my club recommended. Of course this rankled – I had a lovely Aurora 9 in the cupboard which I really wanted to use. Then I made a marvellous discovery, someone has made a device that should solve the incompatibility. 

Assan's wireless buddy box system claims that it can be used across manufacturers. I’ve already got most of the other kit required – two receivers, Hitec and the Futaba and two transmitters the Hitec Aurora 9 and the Futaba 6EX which are incompatible via a buddy lead. I went ahead and purchased the system along with a few extension leads. 


The system arrived and I spent a few hours trying to decipher the instructions. The system itself is a great bit of kit and works fine but the instructions are very poor loosing lots in translation. I’ve rewritten the important parts below. 

The positives for me (the learner) are:

• No distracting cable between trainer and pupil
• Instant switch-over of control
• Allows the use of incompatible systems
• Up to seven channels can be transferred from trainer to pupil so I’ll be able to use the system when I move on to using flaps etc.


The negatives are:

• Additional expense with two receivers required in the model
• Slight additional weight with an extra receiver added to the unit itself and extra cabling

The only compromise I’ve made is the trainer 'deadman' switch, which on the Futaba 6EX does not operate on a channel. I use the switch set to channel 5 (gear) which is a normal on/off. I did look at replacing it with a 'deadman' but it is mounted on a small circuit board which made the change impractical for me. I’ve solved it mechanically by using a short length of silicon tube fitted over the switch and the other end cable tied to the carrying handle. Although a little 'Heath Robinson' it is useful during set up as the pupils Tx can be selected without having to constantly depress the deadman.


Finally problem solved, my instructor has the Futaba 6EX, I get use my precious Aurora 9 and there's no cable linking the transmitters that I find so distracting.

If you’re just starting out please don’t make my rookie mistakes – just because you think you understand doesn’t mean that you do so tell someone at your club about your exact intentions. If you’re not in a club then put it on the forum here and wait for the replies.

MY INSTRUCTIONS – Dual Receiver Switch (Wireless Buddy Box System)
The Assan Dual Receiver Switch may also be referred to as a Wireless Buddy Box System. The Switch allows up to 7 channels to be operated from two separate radio receivers and transmitters in one R/C model.

How to use:
On the switch there are two sets of input connectors, one set labelled Master RX used by the trainer and the other Slave RX used by the pupil. The Master receiver connection has up to seven channels available for connection to servo’s, marked A to G and one to operate the internal switch marked Ctr. The Slave also has up to seven channels also marked A to G. If all seven channels are to be used the master receiver and transmitter must have a minimum of 8 channels. One other connection is available marked BAT, connect your receiver battery here, it will power both receivers and the servos. However if battery connection is made direct to either of the receivers the system will draw power to operate correctly.

You will need a male-to-male extension lead for each channel you are using of the same design as your receivers, plus one for the master control connection.

The labelling on the switch differs to the normal use of the terms CH 1, CH 2 etc. instead opting for alphabetical naming CH A to G, this is because the ports on different makes of receiver may not be the same. The internal linkages within the switch to channel outputs is either operated from the Master channel inputs or Slave channel inputs dependent upon the setting of the Master control input (Ctr).

For example: your Master receiver may use CH 1 for your aileron servo, whereas your Slave receiver may use CH 2 for aileron.  Once Servo A (aileron) is connected to output CH A on the switch, the aileron output from both receivers must be connected to input CH A on Slave (CH 2 to CH A) and Master (CH 1 to CH A) respectively (Figure 3 – wiring diagram).


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