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

Andrew Porrett wap@ica.net [op25-dev] op25-dev at yahoogroups.com
Sat Jun 16 22:20:26 UTC 2018


I don't see how anything in your replies is helpful.

  - They are definitely tone frames.  Tones run through the vocoder 
are irrelevant and OP25 would handle them just fine anyway.

  - Why should the user seek other solutions?  The system is sending 
IMBE tone frames and any decoder thrown at it should handle it.

  - And how does simulcast have anything to do with this?  It doesn't.

To the OP:  You need to record the raw signal (I/Q data or FM 
demodulated audio) so someone can analyze it.  Then the decoder logic 
can be updated to accommodate tone frames and you'll get your audible alerts.


At 04:19 PM 16-06-2018, 'William Becks' wllmbecks at gmail.com [op25-dev] wrote:
>
>
>What exactly are you trying to determine about the tones?   They 
>appear to be “Alert” tones sent by the dispatch operator ahead 
>of the voice message.  I don’t think they actually serve as a 
>signaling function as would commonly be found in analog paging systems.Â
>
>
>
>I believe that someone has already stated that there are only a 
>handful of specific tones or tone combinations that are provided for 
>in the P25 vocoder.  Any other tones or tone combinations 
>transmitted into the speech input of the vocoder quote likely will 
>not reproduce and exact replica as the source tone(s) primarily 
>because the vocoder is designed to encode and compress speech.
>
>Bill, WA8WG

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