invalid signal and noise readings

[ZeroChaos-]

I'm getting json files with signal or noise as 999. I suspect something is wrong, but it's difficult to tell what based on the available information.

Examples:

{
  "freq": 460125000,
  "freq_error": -31,
  "signal": 999,
  "noise": -50,
  "source_num": 3,
  "recorder_num": 42,
  "tdma_slot": 0,
  "phase2_tdma": 0,
  "start_time": 1738480876,
  "stop_time": 1738480879,
  "emergency": 0,
  "priority": 0,
  "mode": 0,
  "duplex": 0,
  "encrypted": 0,
  "call_length": 1,
  "talkgroup": 170,
  "talkgroup_tag": "West PD S-2(Coraopolis)",
  "talkgroup_description": "",
  "talkgroup_group_tag": "Police Dispatch",
  "talkgroup_group": "Allegheny County",
  "audio_type": "analog",
  "short_name": "conv",
  "freqList": [
    {
      "freq": 460125000,
      "time": 1738480876,
      "pos": 0.0,
      "len": 1.0439375,
      "error_count": 50,
      "spike_count": 999
    }
  ],
  "srcList": [
    {
      "src": -1,
      "time": 1738480876,
      "pos": 0.0,
      "emergency": 0,
      "signal_system": "",
      "tag": ""
    }
  ]
}

{
  "freq": 470437500,
  "freq_error": -4,
  "signal": -56,
  "noise": 999,
  "source_num": 9,
  "recorder_num": 52,
  "tdma_slot": 0,
  "phase2_tdma": 0,
  "start_time": 1738510990,
  "stop_time": 1738511278,
  "emergency": 0,
  "priority": 0,
  "mode": 0,
  "duplex": 0,
  "encrypted": 0,
  "call_length": 180,
  "talkgroup": 99,
  "talkgroup_tag": "West EMS Dispatch Identified",
  "talkgroup_description": "",
  "talkgroup_group_tag": "EMS Dispatch",
  "talkgroup_group": "Allegheny Country",
  "audio_type": "analog",
  "short_name": "conv",
  "freqList": [
    {
      "freq": 470437500,
      "time": 1738510990,
      "pos": 0.0,
      "len": 180.0841875,
      "error_count": 999,
      "spike_count": 56
    }
  ],
  "srcList": [
    {
      "src": 4221,
      "time": 1738510990,
      "pos": 0.0,
      "emergency": 0,
      "signal_system": "",
      "tag": ""
    }
  ],
  "multimon_ng": []
}

(I add the multimon_ng key but I didn't manipulate the noise or signal)

[xmleger]

I am seeing similar issues on my setup as well.

I was attributing it to local noise intrusion and had been mitigating alot of it by increasing the minduration to around 1 or 1.5 seconds. A few still occasionally get through though with the audio sounding similar to the noise captured if the squelch is set too low.

If it is an intermittent noise intrusion issue and it is generally always a 999db "signal" captured, would setting some high threshold cutoff for signals (really anything over +40 or +50db would probably be suspect) work to curtail this kind of problem?

[ZeroChaos-]

Given the issue reported is for signal and noise of 999 my suspicion is the opposite of yours. I suspect that it an initialization value and the real value was never set for some reason.

[tadscottsmith]

I'm not sure yet why they aren't always getting set to but the 999 is coming from DB_UNSET which is the default value when the recorders start/restart.

https://github.com/robotastic/trunk-recorder/blob/469744619aaaebe645712f27a5d87753fbbccbfd/trunk-recorder/global_structs.h#L8

[xmleger]

Would it help if the initialization value was set to something well below the standard squelch setting? Like -99? That way they wouldn't be initializing with the squelch open?

[xmleger]

OK... the -99 idea did not work.

[taclane]

DB_UNSET isn't being used to set the squelch, it is the default for detected signal and noise values. After a call ends, it attempts to pull these analyzed values out of the channelizer/signal detector blocks, and it should result in a negative number for both.

The use of 999 in this instance is a purposely erroneous return value that cannot overlap with expected signal/noise numbers. It's essentially reporting that the value was unknown, or couldn't be determined for that call.

Why it displays that after a call sometimes is a question we haven't entirely figured out, but it's possible that it might just be something like the recorder being reset before the values get read out.