Provided that the capacitors are in working order, and not just bits of wire vanishing into a ceramic or plastic blob, they should be OK. I would, however, add another across the motor terminals. All capacitors should have their leads as short as possible, this to stop the capacitor lead acting as a transmitter aerial.

The actual value of the capacitors, within very broad limits, is fairly unimportant – what does matter is the type, which needs very good RF performance and high DC resistance. Fortunately, disc ceramics are among the cheapest components available.

For what is worth, I've never used capacitor to case – I hold to the view that if the single one across the motor terminals doesn't do the job, I need to pay attention to the motor by cleaning the comm and possibly doing something with the brushes. On that occasion, mending the motor with a new one worked best.

Did I mention keeping the capacitor leads short?

If the motor leads are more than a few cm long, twist the pair. The idea is that any interference that is being radiated by the wires will be equal and opposite, cancelling out. Unless one of the tag to case capacitors is duff. In which case the supression arrangement becomes an interference enhancer.

I would endorse the previous posts also, mount the RX antenna (aerial) as far from the motor/wiring as practical.

Malcolm "For what is worth, I've never used capacitor to case – I hold to the view that if the single one across the motor terminals doesn't do the job, I need to pay attention to the motor"

This is very true, fitting Caps. to the motor case (Ground) does little or no good, in most cases since the motor case is not connected to ground. I don't fit them either.

Tom

Hi from the deep south. I have a similar question. I have a Speed 600 motor with a 5 nanofarad capacitor across the terminals and a 1 nanofarad from each terminal to case. I want to add capacitors to a Speed 450 motor. The question I have is whether the size of motor makes any difference. From what Malcoplm says, the answer probably is that it does not make any difference. Would that be a fair assumption? Thanks. Brian

Thanks Tom. Interesting that with the advent of brushless motors, the existance of such things as suppressors is becoming scarce in this neck of the woods, and I had to go to an electronics supplier to source them, the hobby shops no longer stocking such things. I must say that going brushless is quite tempting when looking for a suitable motor in new installations for a number of reasons, efficiency (increasing the length of run) and power (smaller and lighter motor) being two of them. A whole new ball game. Cheers. Brian

Here is chapter and verse on motor suppression from an acknowledged expert on model boat electronics

**LINK**

……..and yes – it's the twisting that matters

Dave M

Thanks Dave and Malcolm. Twisting it is then. Who was it – Chubby Checker (Sp??) I think? Cheers. Brian