High Frequency Motor Drive

DCC decoders pulse (turn on and off) the power to the loco motor - the longer the pulses, the faster the motor runs. Full voltage is always applied.

Early decoders did this at a low frequency (well in the range of human hearing) which made the motor jerk at the drive frequency and harmonics of it. Many would sing as well. Manufacturers provided drive frequency adjustments to minimize these issues.

Then came high frequency drive which operates the decoder beyond the upper limit of human hearing and well beyond any mechanical resonant frequencies. (called Silent Running, Quiet Drive, SuperSonic, etc. by various manufacturers.) It fixed the singing and jerking.

However, a new problem entered - reduced torque at low throttle settings. Several manufacturers came up with a method to compensate for this loss of torque and called it simply torque compensation. TCS called it dither and that moniker stuck. This is a bit like taking one drug to counteract the adverse effects of another!

Some, manufacturers, like TCS and NCE, provid some adjustments for their torque compensation. Others, like Digitrax, just allow you to turn it on or off. Check the manual for your decoder to see what options you have and which CVs control what. Or use DecoderPro (CLICK HERE) to guide you through the maze.

I recommend you read my page on Back EMF (BEMF) decoders, too. CLICK HERE

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