Two way radios - Icom America Inc.

Audio Clarity

We learned from our long distance telephone carriers that digital circuits allowed us to "hear a pin drop" - something the analog lines could never do. Now the clarity of digital technology has found it's way into two-way radios with IDAS.

Analog audio degrades continuously as the distance from the source grows, whereas the digital signal remains more or less constant until it reaches its threshold distance. Essentially, more information is delivered at a further distance. For example, someone may wish to transmit the information "the rain in Spain falls mainly on the plain." Yet, an analog system, at the threshold distance away from the transmitter, may make the information delivered "uh ain in pain alls mainee aw the play." Information is lost and the receiver may misinterpret or be forced to ask for a retransmission. In the IDAS digital system the information delivered would be much closer to the original at the same distance.

The following three sound files are actual recording at the outer fringe of the radio coverage area.

Analog Wide Mode 25kHz
Analog Narrow Mode 12.5kHz
IDAS Digital Mode 6.25kHz

audio clarity chart

The improvement of digital audio is a result of several factors, with the primary two being the latest vocoding technology and forward error correction. The vocoder selected for IDAS was specifically designed to operate in high ambient noise environments. And since the voice (and data) are digital signals, they are encoded and packaged with error correction bits, so the receiving end has the opportunity to correct lost or corrupted bits. The end result is your coverage footprint is wider with crystal clear audio.