11 ms·

Intro to SDR and RF Signal Analysis

246 points by pentestercrab 9y ago

pentestercrab 9y ago
For anyone interested in Software-defined radio (SDR) I can also highly recommend the Cyberspectrum YouTube channel [1]. [1] https://www.youtube.com/playlist?list=PLPmwwVknVIiXGzKhtimTMjhcyppeRRsnE https://www.youtube.com/playlist?list=PLPmwwVknVIiXGzKhtimTM...
- pentestercrab 9y ago
  There is also meetup groups in San Francisco [1] and Melbourne (Australia) [2]. [1] https://www.meetup.com/en-US/Cyberspectrum/ https://www.meetup.com/en-US/Cyberspectrum/ [2] https://www.meetup.com/en-US/Cyberspectrum-Melbourne/ https://www.meetup.com/en-US/Cyberspectrum-Melbourne/
  - bigiain 9y ago
    Not at _all_ surprised to see Balint Seeber's name prominently in some of those links... That guy gives some _amazingly_ interesting talks - I got into SDR pretty much purely based on a presentation of his at DorkBot in Sydney a long time back...
  - audi100quattro 9y ago
    Thanks for posting links to the videos and the meetup group, would've joined it years ago if I'd known about it. Quick question, anything radar related in the videos?
    - bigiain 9y ago
      Have you seen this: http://www.rtl-sdr.com/passive-radar-dual-coherent-channel-rtl-sdr/ http://www.rtl-sdr.com/passive-radar-dual-coherent-channel-r... I can't find the link here right now, but there's some more recent work that's doing that without needing the two clock synced receivers too...
      - audi100quattro 9y ago
        Looking at http://www.rtl-sdr.com/tag/passive-radar/ http://www.rtl-sdr.com/tag/passive-radar/ and youtube, it seems like some progress has been made. Not sure if any of the code is open sourced in GNU Radio, Desktop SDR or http://www.rtl-sdr.com/big-list-rtl-sdr-supported-software/ http://www.rtl-sdr.com/big-list-rtl-sdr-supported-software/ Will look into it more, it's been 2+ years since the last time.
- deleted 9y ago
  [deleted]
- fellellor 9y ago
  Thanks for the links. I's also recommend http://www.desktopsdr.com/ http://www.desktopsdr.com/ It's a course that relies heavily on MATLAB though.
p00b 9y ago
For what it's worth, Great Scott Gadgets (Michael Ossman's group) put out a great series of primers [1] on Software Defined Radio (SDR) and the fundamentals of Digital Signal Processing (DSP) a while back, that are some of the best I've seen out there to date. [1] https://greatscottgadgets.com/sdr/ https://greatscottgadgets.com/sdr/
forg0t_username 9y ago
If you want to dabble for _cheap_ with SDR, the RTL-SDR [1] is a < $10 USB receiver that works from 24 to 1766 MHz. It allows to listen to FM radio, decode most 433MHz devices (weather stations), car keys signals, and even NOAA weather satellites [2] with a DIY antenna [3]. [1] https://osmocom.org/projects/sdr/wiki/rtl-sdr https://osmocom.org/projects/sdr/wiki/rtl-sdr [2] http://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weather-satellite-images/ http://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weath... [3] http://tinhatranch.com/how-to-build-a-qfh-quadrifilar-helix-antenna-to-download-images-from-weather-satellites/ http://tinhatranch.com/how-to-build-a-qfh-quadrifilar-helix-...
- echelon 9y ago
  Can you suggest something that could be used to read or reprogram wireless access cards, such as the HID Proxcard II? I want to clone my apartment's key fob into a bracelet I can wear when I go jogging.
  - voltagex_ 9y ago
    If you have an Android phone, grab a NFC reader app - this should at least tell you if the card is able to be cloned.
    - gfv 9y ago
      Not all RFID cards are created the same. Most RFID cards that are some kind of "smart" (i.e. contactless bank cards, subway tickets) conform to ISO/IEC 14443 standard that mandates the use of ~13.5MHz carrier to communicate between the reader and the card. This is "the NFC" as your phone understands it. Proximity cards used for door access usually have the 125kHz carrier compatible with the EM-Marin EM4100. No cell phones I know of have an antenna for this frequency range; therefore, no phone can read, clone or emulate an EM-Marin proximity card. Since the HID Proxcard II is a "value priced 125 kHz proximity card", you cannot use a phone to read it.
      - voltagex_ 9y ago
thinkMOAR 9y ago
Great intro, and nice links in the comments, excellent!
fellellor 9y ago
Are there companies/sectors that look for candidates with these skills, or is this more focused towards hackers and hobbyists?
- femto 9y ago
  Virtually every professional radio is software defined to some extent these days, so every company that designs radios wants signal processing and information theory skills, more so if they are doing proprietary protocols rather than implementing a standard. It's pretty well the same skill set, whether you are designing or analysing systems. There is a surprising amount of reverse engineering in building radio systems, as the big players (looking at you Motorola) often drop speed humps into their implemetations to try and break compatability with the smaller players' products.
  - fellellor 9y ago
    Where can I read more about this? It's always nice to see RF and Signal Processing stuff on HN.
    - signa11 9y ago
      > Where can I read more about this? there is the canonical Fundamentals of Wireless Communication (https://people.eecs.berkeley.edu/~dtse/book.html https://people.eecs.berkeley.edu/~dtse/book.html) which is pretty good. also, iirc, there is a book by oppenheim as well (signals and systems, i think) edit-00k : yes, oppneheim book is called 'signals and systems' and it is available on ocw as well (https://ocw.mit.edu/resources/res-6-007-signals-and-systems-spring-2011/video-lectures/ https://ocw.mit.edu/resources/res-6-007-signals-and-systems-...)
    - femto 9y ago
      Best thing is to just jump in and do it. You don't even need hardware to start with. If you're seriously interested, download Octave (Matlab replacement) and write a program from scratch to simulate a BPSK system and generate a "waterfall" (bit error vs. noise) curve. Don't stop until you can get your curve to perfectly match the one in a text book [1]. By doing this, you will learn about modulation, demodulation and and "Additive White Gaussian Noise" (AWGN) channel models. If you can get the waterfall curve to match exactly, you will also be covering concepts such as "energy per bit". A BPSK should be quite doable for an amateur. Once you have the BPSK simulation, try extending your simulation in different directions and matching the textbook curves. The following challeges are roughly in order of increasing difficulty 1) Add a block code, such as Hamming or BCH. 2) Replace the simple AWGN channel model with a Rayleigh or Ricean model 3) Add a convolutional code (with Viterbi decoder) 4) Implement Orthogonal Frequency Division Multiplexing (OFDM) 5) Implement an LMS receiver 6) Implement a Low-Density Parity Check code (use the one from the WiFi standard) 7) Implement a complete 802.11a simulation 8) Implement a complete DVB-T simulation 9) Implement a MIMO system, assuming perfect channel knowledge 10) Implement a MIMO system with channel estimation Get to number 10, and you will know more about radio signal processing than most engineers. [1] eg. "Lin and Costello" Error Control Coding or "Proakis" DSP
wonderous 9y ago
Beside HackRF One, I've been looking at LimeSDR. Are there any other comparable options?
- ChuckMcM 9y ago
  Analog Devices has done the ADALM-PLUTO which is less expensive than the HackRF-One. I don't have one of those but I do have the HackRF one, and if UPS is to be believed a LimeSDR :-). The cost/capability matrix is sort of RTL Dongles -> ADALM -> HackRF-1 -> LimeSDR -> Ettus SRP The RTL's don't transmit but all of the other ones can.
- platz 9y ago
  I have a LimeSDR and although multiple channels is nice, the device/software is a bit buggy and I wish I'd gotten a HackRF instead.
- anonymous_iam 9y ago
  BladeRF is pretty cool. It doesn't have quite the frequency range of HackRF, but it's full duplex, and uses 12-bit ADC/DAC (vs. HackRF's 8-bit ones). Also it uses USB 3 so the bandwidth is not limited to 20MHz. (I think it's around 40MHz.)
j_s 9y ago
This discussion from 6 months ago brought together a bunch of introductory info and example applications: https://news.ycombinator.com/item?id=13101924 https://news.ycombinator.com/item?id=13101924
wwkeyboard 9y ago
If you want to see a lot of HF signals, field day is this weekend: http://www.arrl.org/field-day http://www.arrl.org/field-day
anonymous_iam 9y ago
Anyone know the story behind why baudline hasn't been updated in seven years? The site has promised a beta version with some highly desirable features for a LONG time, but nothing. Also, since it's closed source, there's nothing we can do but hope and wait (unless someone were to start an open source equivalent project).

246 points by pentestercrab 9y ago

For anyone interested in Software-defined radio (SDR) I can also highly recommend the Cyberspectrum YouTube channel [1]. [1] https://www.youtube.com/playlist?list=PLPmwwVknVIiXGzKhtimTMjhcyppeRRsnE https://www.youtube.com/playlist?list=PLPmwwVknVIiXGzKhtimTM...

pentestercrab 9y ago
There is also meetup groups in San Francisco [1] and Melbourne (Australia) [2]. [1] https://www.meetup.com/en-US/Cyberspectrum/ https://www.meetup.com/en-US/Cyberspectrum/ [2] https://www.meetup.com/en-US/Cyberspectrum-Melbourne/ https://www.meetup.com/en-US/Cyberspectrum-Melbourne/
- bigiain 9y ago
  Not at _all_ surprised to see Balint Seeber's name prominently in some of those links... That guy gives some _amazingly_ interesting talks - I got into SDR pretty much purely based on a presentation of his at DorkBot in Sydney a long time back...
- audi100quattro 9y ago
  Thanks for posting links to the videos and the meetup group, would've joined it years ago if I'd known about it. Quick question, anything radar related in the videos?
  - bigiain 9y ago
    Have you seen this: http://www.rtl-sdr.com/passive-radar-dual-coherent-channel-rtl-sdr/ http://www.rtl-sdr.com/passive-radar-dual-coherent-channel-r... I can't find the link here right now, but there's some more recent work that's doing that without needing the two clock synced receivers too...
    - audi100quattro 9y ago
      Looking at http://www.rtl-sdr.com/tag/passive-radar/ http://www.rtl-sdr.com/tag/passive-radar/ and youtube, it seems like some progress has been made. Not sure if any of the code is open sourced in GNU Radio, Desktop SDR or http://www.rtl-sdr.com/big-list-rtl-sdr-supported-software/ http://www.rtl-sdr.com/big-list-rtl-sdr-supported-software/ Will look into it more, it's been 2+ years since the last time.
deleted 9y ago
[deleted]
fellellor 9y ago
Thanks for the links. I's also recommend http://www.desktopsdr.com/ http://www.desktopsdr.com/ It's a course that relies heavily on MATLAB though.

p00b 9y ago

For what it's worth, Great Scott Gadgets (Michael Ossman's group) put out a great series of primers [1] on Software Defined Radio (SDR) and the fundamentals of Digital Signal Processing (DSP) a while back, that are some of the best I've seen out there to date. [1] https://greatscottgadgets.com/sdr/ https://greatscottgadgets.com/sdr/

forg0t_username 9y ago

If you want to dabble for _cheap_ with SDR, the RTL-SDR [1] is a < $10 USB receiver that works from 24 to 1766 MHz. It allows to listen to FM radio, decode most 433MHz devices (weather stations), car keys signals, and even NOAA weather satellites [2] with a DIY antenna [3]. [1] https://osmocom.org/projects/sdr/wiki/rtl-sdr https://osmocom.org/projects/sdr/wiki/rtl-sdr [2] http://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weather-satellite-images/ http://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weath... [3] http://tinhatranch.com/how-to-build-a-qfh-quadrifilar-helix-antenna-to-download-images-from-weather-satellites/ http://tinhatranch.com/how-to-build-a-qfh-quadrifilar-helix-...

echelon 9y ago
Can you suggest something that could be used to read or reprogram wireless access cards, such as the HID Proxcard II? I want to clone my apartment's key fob into a bracelet I can wear when I go jogging.
- voltagex_ 9y ago
  If you have an Android phone, grab a NFC reader app - this should at least tell you if the card is able to be cloned.
  - gfv 9y ago
    Not all RFID cards are created the same. Most RFID cards that are some kind of "smart" (i.e. contactless bank cards, subway tickets) conform to ISO/IEC 14443 standard that mandates the use of ~13.5MHz carrier to communicate between the reader and the card. This is "the NFC" as your phone understands it. Proximity cards used for door access usually have the 125kHz carrier compatible with the EM-Marin EM4100. No cell phones I know of have an antenna for this frequency range; therefore, no phone can read, clone or emulate an EM-Marin proximity card. Since the HID Proxcard II is a "value priced 125 kHz proximity card", you cannot use a phone to read it.
    - voltagex_ 9y ago

thinkMOAR 9y ago

Great intro, and nice links in the comments, excellent!

fellellor 9y ago

Are there companies/sectors that look for candidates with these skills, or is this more focused towards hackers and hobbyists?

femto 9y ago
Virtually every professional radio is software defined to some extent these days, so every company that designs radios wants signal processing and information theory skills, more so if they are doing proprietary protocols rather than implementing a standard. It's pretty well the same skill set, whether you are designing or analysing systems. There is a surprising amount of reverse engineering in building radio systems, as the big players (looking at you Motorola) often drop speed humps into their implemetations to try and break compatability with the smaller players' products.
- fellellor 9y ago
  Where can I read more about this? It's always nice to see RF and Signal Processing stuff on HN.
  - signa11 9y ago
    > Where can I read more about this? there is the canonical Fundamentals of Wireless Communication (https://people.eecs.berkeley.edu/~dtse/book.html https://people.eecs.berkeley.edu/~dtse/book.html) which is pretty good. also, iirc, there is a book by oppenheim as well (signals and systems, i think) edit-00k : yes, oppneheim book is called 'signals and systems' and it is available on ocw as well (https://ocw.mit.edu/resources/res-6-007-signals-and-systems-spring-2011/video-lectures/ https://ocw.mit.edu/resources/res-6-007-signals-and-systems-...)
  - femto 9y ago
    Best thing is to just jump in and do it. You don't even need hardware to start with. If you're seriously interested, download Octave (Matlab replacement) and write a program from scratch to simulate a BPSK system and generate a "waterfall" (bit error vs. noise) curve. Don't stop until you can get your curve to perfectly match the one in a text book [1]. By doing this, you will learn about modulation, demodulation and and "Additive White Gaussian Noise" (AWGN) channel models. If you can get the waterfall curve to match exactly, you will also be covering concepts such as "energy per bit". A BPSK should be quite doable for an amateur. Once you have the BPSK simulation, try extending your simulation in different directions and matching the textbook curves. The following challeges are roughly in order of increasing difficulty 1) Add a block code, such as Hamming or BCH. 2) Replace the simple AWGN channel model with a Rayleigh or Ricean model 3) Add a convolutional code (with Viterbi decoder) 4) Implement Orthogonal Frequency Division Multiplexing (OFDM) 5) Implement an LMS receiver 6) Implement a Low-Density Parity Check code (use the one from the WiFi standard) 7) Implement a complete 802.11a simulation 8) Implement a complete DVB-T simulation 9) Implement a MIMO system, assuming perfect channel knowledge 10) Implement a MIMO system with channel estimation Get to number 10, and you will know more about radio signal processing than most engineers. [1] eg. "Lin and Costello" Error Control Coding or "Proakis" DSP

wonderous 9y ago

Beside HackRF One, I've been looking at LimeSDR. Are there any other comparable options?

ChuckMcM 9y ago
Analog Devices has done the ADALM-PLUTO which is less expensive than the HackRF-One. I don't have one of those but I do have the HackRF one, and if UPS is to be believed a LimeSDR :-). The cost/capability matrix is sort of RTL Dongles -> ADALM -> HackRF-1 -> LimeSDR -> Ettus SRP The RTL's don't transmit but all of the other ones can.
platz 9y ago
I have a LimeSDR and although multiple channels is nice, the device/software is a bit buggy and I wish I'd gotten a HackRF instead.
anonymous_iam 9y ago
BladeRF is pretty cool. It doesn't have quite the frequency range of HackRF, but it's full duplex, and uses 12-bit ADC/DAC (vs. HackRF's 8-bit ones). Also it uses USB 3 so the bandwidth is not limited to 20MHz. (I think it's around 40MHz.)

j_s 9y ago

This discussion from 6 months ago brought together a bunch of introductory info and example applications: https://news.ycombinator.com/item?id=13101924 https://news.ycombinator.com/item?id=13101924

wwkeyboard 9y ago

If you want to see a lot of HF signals, field day is this weekend: http://www.arrl.org/field-day http://www.arrl.org/field-day

anonymous_iam 9y ago

Anyone know the story behind why baudline hasn't been updated in seven years? The site has promised a beta version with some highly desirable features for a LONG time, but nothing. Also, since it's closed source, there's nothing we can do but hope and wait (unless someone were to start an open source equivalent project).