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52 lines
2.2 KiB
Markdown
52 lines
2.2 KiB
Markdown
# APCO-25 Decoder #
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The APCO-25 decoder will decoder P-25 phase I signals that are using either
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C4FM modulation or LSM Simulcast (CQPSK) modulation. It will process trunked,
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conventional and packet data messages.
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## Audio Vocoder ##
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APCO-25 Phase-1 audio calls use the multi-band excitation model vocoder to
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compress the digitized audio. SDRTrunk supports the JMBE library for decoding
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audio, but DOES NOT include the jmbe library in the normal application download.
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You must download and compile the library and place the jmbe-x.x.x.jar file in
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the same directory from where you launch the sdrtrunk application. On startup,
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sdrtrunk will attempt to discover the library and can then decode imbe audio.
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[JMBE library](https://github.com/DSheirer/jmbe)
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[How To Setup JMBE](JMBE.md)
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## Traffic Channel Following ##
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The decoder currently does not automatically follow trunked traffic channels.
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This feature is planned for a future release
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## Talkgroups and Addresses ##
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All talkgroups and radio addresses are listed in hexadecimal (base-16) notation
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and use the digits 0 - 9 and the letters A - F. Talkgroups are four characters
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in length and radio addresses are six characters in length.
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Packet data IP Version 4 addresses will normally show in the from column of the
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events window and the Logical Link ID (radio address) will show in the from
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column with the radio's IP Version 4 address listed in the details column. If
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the data contains UDP over IP protocol, the UDP source and destination ports
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will be appended to the IP address.
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## Aliases ##
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You can create an Alias List and attach it to your P25 decoder in the channel
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configuration window.
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When aliasing talkgroups and radio addresses, ensure you include the full 4 or 6
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character talkgroup or address with leading zeros.
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## Modulation ##
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Choose either C4FM or LSM Simulcast (CQPSK) modulation in the channel configuration
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decoder tab. When you select the P25 Decoder from the drop-down list, the
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modulation selector list will appear.
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