[op25-dev] Why can't I hear fire tones?

Andrew Porrett wap@ica.net [op25-dev] op25-dev at yahoogroups.com
Sun May 20 21:24:33 UTC 2018


At 11:35 AM 20-05-2018, nokoa3116 at gmail.com [op25-dev] wrote:

>Do the tones not go like voice over radio.

Generally, no.


>  Is it like a code that the scanner then changes into a beep?

Yes.  Tone frames encode a frequency index and a volume level.  A 
receiver has to synthesize the indicated tone/volume for 20 ms per frame.


Page 20 has a list of AMBE tones:

<http://qsl.net/kb9mwr/projects/dv/codec/TIA-102.BABA-1%20%20P25%20Half%20Rate%20Vocoder%20Addendum%20.pdf>


A slightly different list is found on page 58 here:

<http://dvsinc.com/manuals/AMBE-2020_manual.pdf>


IMBE tone frames are likely similar.

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