Spectrum Painting Richard Shipman MW0RCZ ADARS 6th Jan 2020 - - PowerPoint PPT Presentation

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Spectrum Painting Richard Shipman MW0RCZ ADARS 6th Jan 2020 - - PowerPoint PPT Presentation

Nov 23, 2023 255 likes •490 views

Spectrum Painting Richard Shipman MW0RCZ ADARS 6th Jan 2020 Introduction Introduction Methods Results Discussion Introduction Introduction Methods Results Discussion Introduction Introduction Methods Results Discussion

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SLIDE 1

Spectrum Painting

Richard Shipman MW0RCZ ADARS 6th Jan 2020

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SLIDE 2

Introduction

Introduction Methods Results Discussion

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SLIDE 3

Introduction

Introduction Methods Results Discussion

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SLIDE 4

Introduction

Introduction Methods Results Discussion

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SLIDE 5

Introduction

Introduction Methods Results Discussion

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SLIDE 6

Introduction

Introduction Methods Results Discussion

  • Did you spot it?
  • Text and images scrolling past in the waterfall.
  • I've got to try that...
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SLIDE 7

Introduction

Introduction Methods Results Discussion

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SLIDE 8

Methods

Introduction Methods Results Discussion

  • What is it called?
  • How can I put something cool together?
  • What hardware do I need?
  • Obviously I need a computer and a radio?
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SLIDE 9

Methods

Introduction Methods Results Discussion

  • Useful information on rtl-sdr.com
  • https://www.rtl-sdr.com/tag/spectrum-painter/
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SLIDE 10

Methods

Introduction Methods Results Discussion

  • First thing I found did not even need a radio
  • Rpitx
  • https://github.com/F5OEO/rpitx
  • I have quite a few raspberry Pi computers, but they

were all in use – Abertoir film festival

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SLIDE 11

Methods

Introduction Methods Results Discussion

  • Rpitx transmits direct from a GPIO pin on a PI
  • Just attach a wire as an antenna to GPIO4 (pin 7)
  • But – it is quite noisy, so recommend that you use a band pass filter
  • Subtle warning ón the web page:
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SLIDE 12

Methods

Introduction Methods Results Discussion

  • Second method listed used a HackRF One SDR
  • I have wanted one for a while – so I bit the bullet and

purchased one. (Thanks Ray for the time pressure)

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SLIDE 13

Methods

Introduction Methods Results Discussion

  • Followed the hackaday article
  • https://hackaday.com/2015/08/22/spectrum-painting-o

n-2-4-ghz/

  • Apart from using 2.4Ghz, as that appeared to cause

issues with the simple SDR dongle on the receiver

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SLIDE 14

Methods

Introduction Methods Results Discussion

  • Two computers:
  • 1. transmitter with HackRF One
  • 2. Reciever with SDR dongle and gqrx software
  • I use linux, and command line, but it’s basically 2

steps

  • Prepare the image
  • Transmit the image
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SLIDE 15

Methods

Introduction Methods Results Discussion

  • Prepare the image:
  • Img2iqstream.py from https://github.com/polygon/spectrum_painter
  • Python script:
  • Usage: img2iqstream [OPTIONS] [SRCS]...
  • Options:
  • -s, --samplerate INTEGER

Samplerate of the radio

  • -l, --linetime FLOAT

Time for each line to show

  • -o, --output FILENAME

File to write to (default: stdout)

  • --format [float|bladerf|hackrf]

Output format of samples

  • --help

Show this message and exit.

  • img2iqstream -s 1000000 -l 0.004 -o smiley.iqhackrf --format hackrf examples/

smiley.png

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SLIDE 16

Methods

Introduction Methods Results Discussion

  • Transmit the image
  • hackrf_transfer from hackrf_tools at https://github.com/mossmann/hackrf
  • C program library
  • rcs@stinky /home/rcs $ hackrf_transfer -h
  • Usage:
  • h # this help
  • [-d serial_number] # Serial number of desired HackRF.
  • r <filename> # Receive data into file (use '-' for stdout).
  • t <filename> # Transmit data from file (use '-' for stdin).
  • [-f freq_hz] # Frequency in Hz [0MHz to 7250MHz].
  • [-a amp_enable] # RX/TX RF amplifier 1=Enable, 0=Disable.
  • [-x gain_db] # TX VGA (IF) gain, 0-47dB, 1dB steps
  • [-s sample_rate_hz] # Sample rate in Hz (4/8/10/12.5/16/20MHz, default

10MHz).

  • [-b baseband_filter_bw_hz] # Set baseband filter bandwidth in Hz.
  • Possible

values: 1.75/2.5/3.5/5/5.5/6/7/8/9/10/12/14/15/20/24/28MHz, default <= 0.75 * sample_rate_hz.

  • hackrf_transfer -t smiley.iqhackrf -f 2450000000 -b 1750000 -s 1000000 -x 20
  • a 1
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SLIDE 17

Methods

Introduction Methods Results Discussion

  • Fldigi also has a “videotext” mode
  • You can add a short text message that can be read in the waterfall as a

preamble to a transmission

  • eg. to identify the data mode of the transmission easily.
  • Two rows of 8 characters each.
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SLIDE 18

Results

Introduction Methods Results Discussion

  • Rpitx
  • I didn’t have the time to actually get this working…
  • Didn’t build a band pass filter in time.
  • I did install the software on a pi 4, but didn’t attach an antenna.
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SLIDE 19

Results

Introduction Methods Results Discussion

  • Hackrf
  • After a bit of fiddling got this to work repeatably.
  • Took a bit of experimenting with frequencies and bandwidths
  • Max transmit power is 15 dBm (32mW), frequency dependent.
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SLIDE 20

Discussion

Introduction Methods Results Discussion

  • OK, it is a cool effect, but what use is it?
  • http://www.w1hkj.com/FldigiHelp-3.21/html/id_configuration_page.html
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SLIDE 21

Discussion

Introduction Methods Results Discussion

  • Demo time?
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SLIDE 22

Acknowledgements

  • a
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SLIDE 23

References

  • https://hackaday.com/2015/08/22/spectrum-painting-on-2-4-ghz/
  • https://www.rtl-sdr.com/tag/spectrum-painter/
  • https://www.rtl-sdr.com/painting-on-the-rf-spectrum-with-a-hackrf/
  • https://www.reddit.com/r/amateurradio/comments/3hnpt7/transmitting_

arbitrary_images_viewable_in_the/

  • https://github.com/polygon/spectrum_painter
  • http://jmfriedt.free.fr/lm_fmcapture_eng.pdf