Nexmon SDR: Using the WiFi Chip on a Raspberry Pi 3B+ as a TX Capable SDR

Back in March of this year we posted about Nexmon SDR which is code that you can use to turn a Broadcom BCM4339 802.11ac WiFi chip into a TX capable SDR that is capable of transmitting any arbitrary signal from IQ data within the 2.4 GHz and 5 GHz WiFi bands. In commercial devices the BCM4339 was most commonly found in the Nexus 5 smartphone.

Recently Nexmon have tweeted that their code now supports the BCM43455c0 which is the WiFi chip used in the recently released Raspberry Pi 3B+. They write that the previous Raspberry Pi 3B (non-plus) cannot be used with Nexmon as it only has 802.11n, but since the 3B+ has 802.11ac Nexmon is compatible. 

Combined with RPiTX which is a Raspberry Pi tool for transmitting arbitrary RF signals using a GPIO pin between 5 kHz to 1500 MHz, the Raspberry Pi 3B+ may end up becoming a versatile low cost TX SDR just on it's own.

8 comments

  1. AD5NL

    I did a bit more poking around on Google and I see that the Raspberry Pi 3b+ does not have the pads for a u.fl connector.

    However it does use a Proant PCB resonant cavity antenna similar to the RPi Zero Wireless. And there have been folks who have attached coax or antenna connectors to that model. (Looking at photos there are some differences but it looks like there is basically a trace that would be RF hot).I think it should be possible to cut the trace to the PCB antenna and attach coax there. Which can then be filtered, amplified and otherwise mucked about with RF components.

    Of course this would violate the warranty and the Raspberry Pi Foundation would disavow all knowledge (cue Mission:Impossible theme).

    • AD5NL

      I did some looking. Couldn’t find anything.

      Khadas Vim is another single board computer that may use the same module though.

  2. Languagemaniac_

    I always wanted a raspberry pi but I never bought one but now I’m more into the sdr world and I wanted it more and more and I just read this and I thought “why not?”, I just bought it c’: It’s going to be fun ! I always thought some kind of wifi adapter would be “hacked” to make it an sdr in 2.4ghz band so I’m a little bit excited about this and what it could become. Plus I can use it for other rtl-sdr related stuff and I’m sure it’s a great buy. Thanks for posting this!

  3. AD5NL

    May need external filtering of transmitting outside the ISM bands … Also, does the 3B+ have pads for a u.fl connector? I thought I read those were being removed? Seems kinda pointless without a good antenna connection… Well except for maybe “across-the-lab dx.”

    On the other hand, what chipset does the Orange Pi H3 use? If OPi supported this… And keeps shipping with an antenna jack… It would be super awesome.

    • AD5NL

      Although I suppose one could mount the pi board at the focus of a parabolic dish… Though that seems a tad daft.

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