Listening to South Sound 911 with a RTL-SDR

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Listening with RTL-SDR and OP25

Install OP25 as per these instructions

Create a trunk.tsv file based on the sites you can receive, their control channels, and the site NAC. Here is an example:

"Sysname"      "Control Channel List"                    "Offset" "NAC"   "Modulation"    "TGID Tags File"        "Whitelist"     "Blacklist"     "Center Frequency"
"Tacoma"       "774.68125,774.43125,773.93125"           "-720"   "0x1e1" "C4FM"
"Orting"       "770.35625,770.60625,773.98125,774.48125" "-720"   "0x1e2" "C4FM"
"South"        "773.231250,773.731250"                   "-720"   "0x1e3" "C4FM"
"West Seattle" "774.706250,774.206250"                   "-720"   "0x1e4" "C4FM"
"Buckley"      "773.481250,772.931250"                   "-720"   "0x1e5" "C4FM"

TSV stands for tab-separated values. Each field in the tsv file must be separated by a single tab character. This wiki does not preserve tab characters, so you must fix it after copy and pasting.

You will need to determine the offset needed for your RTL dongle by using the fine tune slider in OP25 to line up the signal on the Datascope tab.

Here is an example command to start OP25 with the above file. You may need to change some of the arguments for your system:

./op25/op25/gr-op25_repeater/apps/ --args rtl=0 -N LNA:42 -f 774081250 -S 2400000 -v 5 -2 -T trunk.tsv