RTL-SDR direct sampling mode

[iw7dle]

Hi there,

I'm testing NovaSDR with RTL-SDR v3 dongle. Everything works well in NORMAL MODE (VHF/UHF) but I don't know hot to configure DIRECT SAMPLING MODE for HF.

Any advise? Thanks.

73 IW7DLE Mario

[iw7dle]

Ok found the additional setting:

> Add SoapySDR device settings? (key=value) Yes
> Setting key (blank to finish) direct_samp
> Setting value 2

73

[Bas ON5HB]

It may help others if you posted your receivers.json to show how you did this.

[iw7dle]

Sure, following the configuration file receivers.json:

Code Select Expand

{
  "receivers": [
    {
      "id": "rx0",
      "input": {
        "accelerator": "none",
        "audio_compression": "flac",
        "audio_sps": 12000,
        "brightness_offset": 0,
        "defaults": {
          "frequency": 14200000,
          "modulation": "USB",
          "ssb_highcut_hz": 3000,
          "ssb_lowcut_hz": 300
        },
        "driver": {
          "channel": 0,
          "device": "driver=rtlsdr, label=Generic RTL2832U OEM :: 00000001, manufacturer=Realtek, product=RTL2838UHIDIR, serial=00000001, tuner=Rafael Micro>
          "format": "cs16",
          "kind": "soapysdr",
          "settings": {
            "direct_samp": "2"
          }
        },
        "fft_size": 131072,
        "frequency": 14175000,
        "signal": "iq",
        "smeter_offset": 0,
        "sps": 1024000,
        "waterfall_compression": "zstd",
        "waterfall_size": 1024
      },
      "name": "rtl-sdr"
    }
  ]
}


[Bas ON5HB]

If you want to control gain, agc etc:

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{
        "id": "rx4",
        "name": "RTL (2M 144-146 MHz)",
        "input": {
                "sps": 2048000,
                "frequency": 145000000,
                "signal": "iq",
                "fft_size": 131072,
                "fft_threads": 1,
                "brightness_offset": -6,
                "audio_sps": 12000,
                "waterfall_size": 2048,
                "waterfall_compression": "zstd",
                "audio_compression": "flac",
                "accelerator": "clfft",
                "smeter_offset": -40,
                "driver": {"kind": "soapysdr","device": "serial=00000001","channel": 0,"format": "cf32","gain": 44,"agc": false},
                "defaults": { "frequency": 145787500, "modulation": "FM" }
                }
        },


See here, works also for other Soapy receivers.

https://github.com/ON5HB/NovaSDR/blob/main/docs/CONFIG_REFERENCE.md