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I have seen mine & many others' (Android) devices nowadays have WiFi hardware capable of connecting with 2.4Ghz & 5Ghz APs. Wanted to know if I could tweak the WiFi driver in the kernel source or at runtime to somehow act as a RF receiver at different frequency e.g., 2.5 or 2.6 Ghz?

I tried googling but found nothing which forces me to assume it is not possible.

If yes, then a how-to would be appreciated. Thanks in advance.

Note: My goal is to be able to receive analog video over RF.

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    \$\begingroup\$ The RF section is unlikely to be easily changed (if at all). \$\endgroup\$
    – Peter Smith
    Jul 22, 2018 at 14:23
  • \$\begingroup\$ I have deep looked into my wlan drivers' source, it has support for many frequencies over different channels. Need to know if I add my desired frequency in there as an extra channel and stream through it. Is it going to work? \$\endgroup\$
    – VPZ
    Jul 22, 2018 at 14:26
  • \$\begingroup\$ Generally speaking, no, and this is too broad (as no specific radio is mentioned). I believe there was something published in the way of an open source project for a few phones with the same radio components, but it would not have done analog RF video. Consider an external USB receiver. \$\endgroup\$
    – Chris Stratton
    Jul 22, 2018 at 14:57
  • \$\begingroup\$ I can't have external accessories. My choices are limited to using what's on the phone already. \$\endgroup\$
    – VPZ
    Jul 22, 2018 at 15:02

3 Answers 3

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analog video over RF

This will not be possible. The only way you might have a chance is if you can edit the card's firmware. However, that will not be possible as you'll need access to the manufacturer's internal documentation and software that probably isn't even available under NDA. And even then, that will only work if the card's hardware is flexible enough, which it probably isn't. And then you would need to write an entirely custom driver that can handle the video data. In short, this would be a massive engineering undertaking that won't be possible without resources you don't have access to as you're not an employee of the WiFi card manufacturer.

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  • \$\begingroup\$ Okay, I am now convincing myself for external hardware. \$\endgroup\$
    – VPZ
    Jul 23, 2018 at 3:40
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Not quite, you'll likely have to get your hands on separate hardware to make this a reality. The devices are hardwired to operate on 802.11 so altering the physical layer to send analog video is unlikely. Typically the hardware is produced only to operate in the legal ranges for all countries. Some countries have wider or narrower requirements. More info here.

Also, legally, you can only transmit between 2.4 and 2.5GHz in most countries.

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The Receiver will have an ADC analog-digital-converter with sample rate fast enough to handle the bandwidth (4-6MHz) of an analog video signal. The number of ADC bits may not be high enough to provide 40 db SNR (about 7 bits). The Receiver phasenoise and the ADC sampling jitter may not be low enough to achieve 40dB SNR (you need 60 dB for a superb video picture).

As other answers stated, the firmware must be changed. Learn how to do that.

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  • \$\begingroup\$ Even if the components exist in the design, very doubtful that the data paths exist to support this. Someone did figure out how to make some Broadcom chips do fairly arbitrary transmission, but that was by using a test mode explicitly built by the manufacturer. No particular reason to believe that a corresponding receive path exists. \$\endgroup\$
    – Chris Stratton
    Jul 23, 2018 at 1:35

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