Advanced Multi Band Excitation

This is the technology that provides the audio compression and decompression for DStar. Seems like a whole lot to take in but we’ve been dealing with audio compression for a long time. Most people have bought and downloaded mp3 or mp4 files. Mp3 or mpeg3 is audio compression technology too.

A typical song is about 3 minutes or 4 minutes long and when uncompressed, it typically is in .wav format and this format can be 5 or 6 times the size of an .mp3 file. So, this .wav format song can be up to 15 to 18 megabytes in its uncompressed size. That would be a lot of data to be streaming or downloading so it is compressed to 3 or 4 megabytes using mp3 compression.

The same principle applies to DStar using the AMBE vocoder (voice encoder/decoder) chip. The chip encodes (compresses) our voice and data into a stream that fits into the 12.5 khz narrow FM signal that we transmit, and when received, the same chip is used in the receiver to uncompress (decode) the signal. What we sacrifice is quality. If we used the same uncompressed audio we expect in an broadcast radio station we would need nearly 3 times the bandwidth when we sum the data with our voice.

The chip is made by a company called Digital Voice Systems Incorporated (DVSI) and is a hardware implementation of audio and data compression compared to a software implementation such as mp3. It is arguable that the hardware implementation is faster and more reliable than a software based vocoder, especially since the DVSI chip has backwards compatibility, is also a analog to digital converter and vice versa, and has even more bells and whistles to fill a couple hundred pages of specifications. So this chip does all of this in one package. That makes the DVSI AMBE chip a good choice for ham radio. We can do all of this stuff on one chip, so it fits nicely into a handy talkie. Everyone knows that hams like HT’s.

I’m not saying that there aren’t other good options out there, I’m not getting into that debate in this article, but many amateur operators choose DStar for a multitude of reasons. I like DStar, DMR, and System Fusion, and the AMBE 3000 chip encodes and decodes them all. It does a good job.

When you buy a DStar radio or a AMBE dongle, or AMBE server you are likely buying the DVSI chip and paying for the license to use that technology. I am certainly glad we have it.


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