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Companding

Who is compander? What is a compander?

 

Well, most, if not all audio engineers know what a compander is, it’s a combination of a compressor (squashes the dynamic range of a signal fed into it) and a expander (pretty much the opposite of a compressor)

So, in simple terms, you have a plastic pint of milk, the bottle is the signal. You have it between your two hands, one hand on top of the pint and the other at the bottom of the pint. When you decide to prove your strength and squash the pint (plastic bottle of milk), you are compressing it, and when you realise you still need to use it and you pull it out again to get it back to its normal self, you are expanding it.

Well, we know that that our analogue radio microphone gives us FM (frequency modulated) signal, and we know that FM is much preferred, when it comes to choosing between FM and AM (amplitude modulation) (topic for another blog). FM will give you clearer audio because it has more dynamic range (difference between lowest and highest), meaning more breathing space for your signal, meaning it sounds more natural.

FM has more dynamic range than AM, but, we need to also understand that it has its limits, it’s not unlimited bandwidth. That’s where there compander steps in. Due to the fact that FM works on a set dynamic range, our brilliant wireless microphone manufacturer engineers built into analogue wireless microphone systems, companders, so that as a signal leaves the microphone or transmitter(TX) it is compressed, so that it fits into the FM carrier, and as soon as the same signal reaches the receiver side, it is expanded back to normal again so it sounds as it sounded when it left the microphone or sounds more natural.

Companding is also meant to increase the signal to noise ratio (SNR). So, after the signal has been compressed and transmitted, it reaches the receiver and the signal that was sent will be increased again so that it is louder than the unwanted system noise.

 

It hope this clears it up for you!!

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