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I'm a novice. I'm trying to communicate wirelessly between an electret microphone and a speaker using HC-12 modules. What I have set up in the picture below works in the sense that a signal is sent to the speaker when I blow hard enough on the electret microphone, seemingly indicating that everything may in fact be wired correctly. However, the speaker just makes a deep buzzing noise that doesn't at all resemble the sounds that go into the microphone.

You can see in the picture that I'm using two amplifier modules - one for the transmitter and one for the receiver. I'm powering the transmitter with a rechargeable 9V battery and the receiver with 3 rechargeable AA batteries (~3.8 V).

I've verified that the HC-12 modules being used work independently. I've also verified that the microphone, amplifiers, and speaker work (when connected via wires, audio signal is transmitted just fine from the microphone to the amplifier to the speaker).

Can someone help me to identify what I'm missing?

my unsuccessful attempt at wirelessly communicating between a microphone and speaker

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  • \$\begingroup\$ Use a series R from Rx DC power with a low ESR e-cap to suppress ripple or a local LDO on breadboard. Rx designs expect you supply clean DC power with no ripple. It can be DM or CM so you may also need a ferrite choke like VGA cables. \$\endgroup\$ – Sunnyskyguy EE75 Apr 10 '18 at 2:39
  • \$\begingroup\$ Thank you for your response. As a novice, I'm having difficulty parsing it. Are you suggesting that I try putting a resistor and a capacitor in series between Vcc and the pin on the HC-12 that accepts power on the receiver? That wouldn't seem to make sense to me, but I really am very confused about how to interpret what you wrote. \$\endgroup\$ – lostinthecloud Apr 10 '18 at 2:52
  • \$\begingroup\$ We don't know what you are doing there, i.e. what is connected where. A schematic is needed. Also datasheets for the involved modules/ICs \$\endgroup\$ – PlasmaHH Apr 10 '18 at 6:30
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This does not work because the HC12 is a digital data radio based on the Si446x series chips, not an analog audio link.

You should select instead a radio suitable for your goals. There are 2.4 GHz wireless audio links available, for example.

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  • \$\begingroup\$ Thank you for your response. Would the NRF24L01 radio module suffer from the same problem? If so, it seems that issue can be overcome with some clever programming (see video: youtube.com/watch?v=2ZK6dcBTeT0). Is that what I need to do to get things to work with the HC-12s? Do I need to figure out how to "digitize" the audio signal? \$\endgroup\$ – lostinthecloud Apr 10 '18 at 3:10
  • \$\begingroup\$ @lostinthecloud An nRF24 isn't really ideal for digital audio either; it can probably be done, but why go to all the trouble of building digitizers to force data through a not-really-suited radio, when there are things made specifically for this purpose??? \$\endgroup\$ – Chris Stratton Apr 10 '18 at 17:22
  • \$\begingroup\$ Can you point me to such a product that is small, intended for a DIY project, and inexpensive? \$\endgroup\$ – lostinthecloud Apr 10 '18 at 23:24
  • \$\begingroup\$ Oh OK, I guess you were just being nasty. Check this out, you might like it: youtube.com/watch?v=w_Opt9bJlqg \$\endgroup\$ – lostinthecloud Apr 15 '18 at 17:38

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