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I have developed a radio driver that can detect sensor RF packets for a particular protocol, in 433 MHz band using a 433 MHz receiver module like this one and also similar to this one. Before I started with the software implementation, I was given a sound card to which the receiver module was connected. I connected this sound card + receiver module to my PC- USB and was able to capture and visualize the RF packets using an audio editing software known as GoldWave-Link.

My question is: How is it possible for a sound card to detect 433 MHz RF signals, whats the principle behind it?

Another question is, on a PC sound card hardware, how do I figure out which points is the Vcc, GND and data input?. For a sound card like this one here

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  • \$\begingroup\$ which receiver module? \$\endgroup\$
    – tcrosley
    Dec 8, 2016 at 5:59
  • \$\begingroup\$ I have update the question with the link of the modules \$\endgroup\$
    – PsychedGuy
    Dec 8, 2016 at 6:03
  • \$\begingroup\$ The receiver module detects (and decodes) it. The sound card only sees the baseband signal. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Dec 8, 2016 at 6:04
  • \$\begingroup\$ if 433mhz rf signal is in air means then all 433mhz receiver will receive those signals, open the case then check which IC is used and look at that IC's data sheet \$\endgroup\$
    – masternone
    Dec 8, 2016 at 6:05
  • \$\begingroup\$ Your sound card is detecting the low frequency data after the receiver has recovered it from the radio signal. Its like asking how can your sound card record music from an FM radio set to 98.7 MHz. Your sound card can't do anything with the RF, but it can easily handle the demodulated audio signal. \$\endgroup\$
    – JRE
    Dec 8, 2016 at 6:14

2 Answers 2

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How is it possible for a sound card to detect 433 MHz RF signals?

A PC sound card CANNOT detect much above 20KHz. It most certainly cannot detect anything at 100s of MHz.

whats the principle behind it?

A "receiver" is a device that detects the Radio Frequency signals and converts it into an audio signal that your sound card can detect.

on a PC sound card hardware, how do I figure out which points is the Vcc, GND and data input?

You linked to a USB audio "card". The gadget uses standard USB for power, ground, and serial data in both directions. How USB works is well documented and you should have no problem learning about USB.

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Receiver demodulates the low-frequency information carried by 433MHz. The soundcard can detect audio (or low-frequency) signals coming from your receiver.

It is no different if you've connected an FM radio receiving around 100MHz to your soundcard and recorded the music.

In your case it is not 100MHz but 433MHz and it is not music but a digital signal.

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