5 ms·

Side question: there's no way to get low-level access to the WiFi adapter in a MacBook Pro, right? It would be nice if I could do SDR stuff with the radio anten

by md224 8y ago

Side question: there's no way to get low-level access to the WiFi adapter in a MacBook Pro, right? It would be nice if I could do SDR stuff with the radio antenna that came with my computer... though I'm guessing it's not the right type of antenna anyway.

stefan_ 8y ago
WiFi adapters are not SDR, lots of the protocol will be implemented in hardware/firmware of the chip.
- tlrobinson 8y ago
  Not always true: https://www.rtl-sdr.com/nexmon-sdr-turning-a-broadcom-802-11ac-wifi-chip-into-a-tx-capable-software-defined-radio/ https://www.rtl-sdr.com/nexmon-sdr-turning-a-broadcom-802-11... (not sure if it normally uses SDR, probably not, but it does provide low-level access needed for SDR)
pjc50 8y ago
Usually the radio is fixed-band, but the receive and transmit digital side will usually be some combination of fixed-function pipeline and actual DSP software. The problem is that the information needed to reprogram them is highly proprietary.
- cedivad 8y ago
  Yep, you need to be DJI or similar to get access to them. Very discouraging as a small fish. (I've looked into the broadcom-based project above, unfortunately it's not suitable for continuous reception/transmission, and you would still need processing power anyway).
freedomben 8y ago
Yes, the wifi antennas are very specifically sized for the 802.11 frequency ranges. They also often have band pass filters built in to prevent transmissions outside of those bands, as required by FCC regulations and such. That said, if you are really interested in that kind of thing, and you are willing to switch to Linux, the wireless card drivers are very hackable. Source: I forked the driver for my wireless card many years ago and still maintain it, tho these days it's mostly the upstream kernel driver plus a few hacks to get the most out of the hardware: https://github.com/FreedomBen/rtl8188ce-linux-driver https://github.com/FreedomBen/rtl8188ce-linux-driver
- tuxxy 8y ago
  Damn, this is really cool. Great work! Small question: how much does this affect power on the laptops you've used this on?
  - freedomben 8y ago
    Thank you! I'm sorry I'm not totally sure what you are asking. Are you asking how much does it drain the laptop battery? To be honest I've never really tested that, but I'm curious now :-) If you are asking how much the driver affects the transmit power of the wireless card, it takes it from 20 dB up to 33 dB, and each 3 dB is a doubling of power, so it cranks it up by a significant amount.
    - tuxxy 8y ago
      Yes, I was curious about how much this affects battery drain. It seems like it would be a considerable amount.
newman8r 8y ago
nah, and rtl-sdr units are under $20 so you should look into picking one up, they're a blast. You can actually create a transmitter out of a sound card though, it's kind of a fun experiment https://dspillustrations.com/pages/posts/misc/using-your-soundcard-for-hands-on-digital-communication.html https://dspillustrations.com/pages/posts/misc/using-your-sou... Some people have also tried to create a wifi interface from SDR transceivers, but they're extremely inefficient.

by md224 8y ago

stefan_ 8y ago

WiFi adapters are not SDR, lots of the protocol will be implemented in hardware/firmware of the chip.

tlrobinson 8y ago
Not always true: https://www.rtl-sdr.com/nexmon-sdr-turning-a-broadcom-802-11ac-wifi-chip-into-a-tx-capable-software-defined-radio/ https://www.rtl-sdr.com/nexmon-sdr-turning-a-broadcom-802-11... (not sure if it normally uses SDR, probably not, but it does provide low-level access needed for SDR)

pjc50 8y ago

Usually the radio is fixed-band, but the receive and transmit digital side will usually be some combination of fixed-function pipeline and actual DSP software. The problem is that the information needed to reprogram them is highly proprietary.

cedivad 8y ago
Yep, you need to be DJI or similar to get access to them. Very discouraging as a small fish. (I've looked into the broadcom-based project above, unfortunately it's not suitable for continuous reception/transmission, and you would still need processing power anyway).

freedomben 8y ago

Yes, the wifi antennas are very specifically sized for the 802.11 frequency ranges. They also often have band pass filters built in to prevent transmissions outside of those bands, as required by FCC regulations and such. That said, if you are really interested in that kind of thing, and you are willing to switch to Linux, the wireless card drivers are very hackable. Source: I forked the driver for my wireless card many years ago and still maintain it, tho these days it's mostly the upstream kernel driver plus a few hacks to get the most out of the hardware: https://github.com/FreedomBen/rtl8188ce-linux-driver https://github.com/FreedomBen/rtl8188ce-linux-driver

tuxxy 8y ago
Damn, this is really cool. Great work! Small question: how much does this affect power on the laptops you've used this on?
- freedomben 8y ago
  Thank you! I'm sorry I'm not totally sure what you are asking. Are you asking how much does it drain the laptop battery? To be honest I've never really tested that, but I'm curious now :-) If you are asking how much the driver affects the transmit power of the wireless card, it takes it from 20 dB up to 33 dB, and each 3 dB is a doubling of power, so it cranks it up by a significant amount.
  - tuxxy 8y ago
    Yes, I was curious about how much this affects battery drain. It seems like it would be a considerable amount.

newman8r 8y ago

nah, and rtl-sdr units are under $20 so you should look into picking one up, they're a blast. You can actually create a transmitter out of a sound card though, it's kind of a fun experiment https://dspillustrations.com/pages/posts/misc/using-your-soundcard-for-hands-on-digital-communication.html https://dspillustrations.com/pages/posts/misc/using-your-sou... Some people have also tried to create a wifi interface from SDR transceivers, but they're extremely inefficient.