39 lines
1.6 KiB
Plaintext
39 lines
1.6 KiB
Plaintext
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Linking OP25 TX and RX December 2020
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===================================================================
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The OP25 TX application can be configured to transmit one or more
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channels directly to one of the RX apps (rx.py or multi_rx.py) in
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each case by specifying a device args string of the form
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udp:host:port
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where host and port are the IP address and UDP port number,
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respectively. Typically, the TX is started first followed by
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the RX, but they can be started in any order. UDP port 25252 is
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used in the examples.
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The sample RX script is in runudp.sh, and the sample TX json config
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is in cfg-900.json .
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To start the TX
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cd .../op25/op25-gr_repeater/apps/tx
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./multi_tx.py -c ../cfg-900.json
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The RX is started with
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cd .../op25/op25-gr_repeater/apps
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./runudp.sh
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There is a 120KHz sized block of spectrum transmitted (SR=120000)
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which is treated as complex baseband with each side pretending that
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the spectrum is converted to/from the 900 MHz band. On the RX side
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any frequency-change requests are ignored; instead, a "center
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frequency" is defined. There are two channels (P25 trunk control
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channel and P25 voice channel) spaced at 50 KHz separation.
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The TX reads two data files that must be created beforehand. To
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create the trunk control channel data symbol file, refer to
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tx/README-fakecc.txt
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An audio file (PCM/ rate 8000 / mono / signed int16) must also be
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created - this file will be real-time encoded with the voice codec
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and sent on the P25 voice channel. These two files must be defined
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in the cfg-900.json file (channel "source" keyword).
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