SDR

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Hardware

HackRF

$ hackrf_info
Found HackRF board.
Board ID Number: 2 (HackRF One)
Firmware Version: 2014.08.1
Part ID Number: 0xa000cb3c 0x0067434c
Serial Number: 0x00000000 0x00000000 0x15d463dc 0x383f8125

Airspy

  • 24MHz - 1.750GHz, RX, BW 10MHz (9MHz alias free), ADC 12bit (10.4 ENOB)
  • Bias-T supply can deliver 4.5V
  • FW flashing
$ airspy_info

Found AirSpy board 1
Board ID Number: 0 (AIRSPY)
Firmware Version: AirSpy NOS v1.0.0-rc5-0-g648c14f 2015-05-20
Part ID Number: 0x6906002B 0x00000030
Serial Number: 0x618C63C82F7424A7
Supported sample rates:
	10.000000 MSPS
	2.500000 MSPS
Close board 1

RTL-SDR

  • ~25MHz - 2GHz, RX, BW 2.4-2.8MHz, ADC 8bit
  • Mine: 52-2212 MHz with gap @ 1107-1241 MHz

LNA: Low Noise Amplifiers

  • LNA4ALL
    • 28-2500MHz, gain about 22dB from 28MHz to 600MHz then gain drops to ~16dB @ 1400MHz and ~11dB @ 2500MHz, 0.75dB NF @ 1 GHz and 0.98dB NF @ 2 GHz
    • 6-9 V, 55-65 mA (5V if regulator bridged)
    • can be powered by HackRF or Airspy if modified, 10uH SMD on OUT and regulator bridged (because we deliver <5V) or bridged by 100mA fuse, just in case.
  • LNA4HF
    • 150kHz - 30MHz, gain 18-20 dB, NF 1-2 dB
    • 6-9 V, 18 mA (5V if regulator bridged)
    • up to 2GHz if low-pass filter removed
  • Better to position LNA near antenna than near receiver, more useful info here

Antennas

ANT500

  • 50 ohms, 75 MHz - 1 GHz, 20cm - 88cm

Software

Reverse engineering

Info

Generic

GQRX

Baudline

With hackrf


Add offset to avoid DC, e.g. to monitor 440MHz -> 442MHz
E.g. somewhere around 100MHz @ 8MHz:

hackrf_transfer -r /dev/stdout -f 100000000 -s 8000000 | \
  baudline -stdin -quadrature -channels 2 -flipcomplex -format u8 -samplerate 8000000 -memory 256

With airspy


Freq is given in MHz, sample rate is given by fw offset: -a 0 = 10M, -a 1 = 2.5M
By default airspy_rx & baudline work with 16bit LSB samples

airspy_rx -r /dev/stdout -f 100 -a 0  | \
  baudline -stdin -quadrature -channels 2 -flipcomplex -samplerate 10000000 -memory 256
airspy_rx -r /dev/stdout -f 100 -a 1  | \
  baudline -stdin -quadrature -channels 2 -flipcomplex -samplerate 2500000 -memory 256

After demodulation with GQRX

In GQRX, choose to stream audio through UDP (icon on left of recording button)

nc -l -u -p 7355  | \
  baudline -stdin -samplerate 48000

Tuning

  • input / color aperture
  • zoom: alt+arrows
  • Hz zoom: require larger FFT (process / transform size), trade-off with temporal resolution

27MHz RC

87MHz to 108MHz FM band

315MHz car keyfob

480MHz interferences

Stripes around 480MHz are because of poorly shielded USB cable

524 to 542 MHz wireless microphones

1090MHz ADS-B

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