antispy-jammer

Simple ultrasonic antispy voice recording jammer based on ARDUINO module and power output stage for driving piezzo ultrasonic transducers. It prevents from unauthorized human speech recording by hidden microphones and voice assistants.
Initially ATTINY were used along with AD9833 programmable signal generator and audio amplifier PAM8403 / TPA3116D2 module driving piezo. Using different Arduino boards like Raspberry Pi Pico RP2040-Zero, ESP8266/ESP32, Arduino Mini/Nano is also possible with older software as long as they support hardware SPI connectivity.
Current development is focused on RP2040 + MOSFET stage as it has better cost and jamming efficiency.

The project is based on following concept presented here : https://sandlab.cs.uchicago.edu/jammer/ , here https://github.com/y-x-c/wearable-microphone-jamming
and here http://people.cs.uchicago.edu/~ravenben/publications/pdf/ultra-chi20.pdf , however my design evolved and using AD9833 and 25kHZ transducers is the only similarity with the original project.

There are 3 versions of the jammer :

• Obsolete : version A with ATTINY85/Digispark only and audio amplifier TPA3116D2 + 20 transducers. This version is a bit audible and may not be preferred by some people. Less audible version is with TC4420 / IXDN614PI ( NON INVERTING MOSFET driver chip ) + MOSFET IRFB4115 + transducer + coils.

• Not further developed : version B with ATTINY85/Digispark (or RP2040/ESP8266/ESP32) + AD9833 Signal Generator + audio amplifier TPA3116D2 ( XH-M542 ) / or MOSFET driver chip + 20 transducers + additional components like Coils and Mosfet. This version is barely audible and has outstanding jamming capability for newest mobile phones like iPhone.

• version C with RP2040 + MOSFET driver chip + MOSFET + 20-80 transducers + Coils. This is the latest revision which is barely audible and has outstanding jamming capability for newest mobile phones like iPhone. There are two revisions of this version C - With single MOSFET + driver and with Full H-bridge and 4 MOSFETS + 2 MOSFET bridge drivers. The signal is enterily generated by PWM in RP2040 chip, rectangle wave further drives MOSFET output stage.

If thinking about older project versions please notice that some audio amplifiers like TPA3110 do not work correctly with ultrasonic transducers (only some "clicking" sound and no ultrasound). So far I have found only PAM8403 and TPA3116D2 modules to work properly. Anyway I finally recommend to use only ORIGINAL TPA3116D2 due to its audio power (watch out for fake XH-M542 boards!). Due to many fake Audio amplifier boards XH-M542 I am using now only following setup : TC4420 ( mosfer driver chip ) + MOSFET IRF4115 + transducer + coils OR alernatively H-Bridge with IR210X. They differ in terms of the coil placement - in PARALLEL for single MOSFET solution, in SERIES for H-bridge version. The single MOSFET jammer solution draws a lot of current due to LC tank circuit. Powering it from Li-Ion battery is a must. The H-bridge MOSFET jammer has better energy efficiency and this version can be powered from small power brick (depending on number of transducers used).

Please keep in mind that ONLY 25KHz transducers and code are working properly for all types of microphones/devices. The 40KHz have very limited jamming capability and should not be used, however the source code for this frequency is available in the repo.

History of version C of the jammer :

04.2026 - added Raspberry RP2040 / RP2035 jammer version without AD9833 module. This boards uses perfect PWM that is built in within RP2040 chip to generate the same signal as AD9833 in previous versions. This reduces the cost and improves reliability of the device ( I found many chinese AD9833 modules poor quality ). Added KICAD DESIGN files + GERBER files for the PCB (PCBWAY / JLCPCB ).

06.2026 - added Raspberry RP2040 version with H-Bridge. This board uses PWM signal generation in RP2040 and 4 MOSFETS + 2 MOSFET drivers. The advantage is better iPhone jamming. The coil must be adjusted to the number of transducers and is connected in SERIES with parallel set of transducers. Initial starting coil value is 47 MICROHENR for 20 transducers 25KHz (2nF each). The more transducers the lower the inductance should be. Added KICAD DESIGN files + GERBER files for the PCB (PCBWAY / JLCPCB ).

07.2026 - changed the code to use Sinusoidal wave FM modulation of 25KHz bearer. It turned out that random 20-50Hz sinsusoidal modulation signal in small samples (from 1 to 10 milisecond timing) makes the Automatic Gain Control in the phones go out of sync and gives outstanding results in jamming expensive phones.

IF YOU WANT TO INCREASE JAMMING CAPABILITY YOU CAN USE MORE TRANSDUCERS LIKE 60-80 PER AUDIO CHANNEL FOR BOTH VERSIONS : MOSFET DRIVER TC4420/IXDN614PI + MOSFET IRFB4115 + COIL OR H-BRIDGE MOSFET + COIL !

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VERSION C

In this revision RP2040 chips take over signal generation entirely with perfect PWM function. It improves stability of the solution and further reduces cost of manufacturing. This version operates only with MOSFET drivers and MOSFETs, there is no option to use audio amplifier board here (you may try but you would need to get rid of the coil). Use free software KICAD to see the schematic & PCB. The software can be flashed directly by dragging UF2 file to RP2040 USB disk drive ( RP2040 module must have pressed BOOT key while attaching to the PC over USB). You do not even need Arduino environment to flash the SW.

Components used version C :

• 1 x Microcontroller RP2040-ZERO or RP2040-ONE for PWM signal generation
• 1 x 470uF - 2200uF LOW ESR microfarad electrolytic capacitor ( for blocking distortions on power lines GND / 12V )
• 1 x 10uF - 100uF microfarad electrolytic capacitor ( for blocking distortions on power lines GND / 5V )
• 2 x 220nF - 680nF capacitor (for blocking distortions on power lines)
• set of 25kHZ (resonance frequency is important !) ultrasonic piezo transducers like NU25C16T-1, 25kHz or equivalent. Minimum 15-20 for jamming efficiency. Recommended 60+ transducers
• power source - minimum 2x18650 LiIon cells + XL6009 step-up voltage converter ( for single MOSFET solution ) or 12V-15V / 2A power brick ( for H-Bridge solution ). Recommended powering voltage for both versions is 15V. Do not go over 18V (you will break MOSFETs)
• LM7805 - 5V voltage stabilizer for powering RP2040
• MOSFET DRIVERS : TC4420 for single MOSFET solution (alternatively better IXDN614PI can be used or any other compatible with pinout), 2 x IR2104 / IR2103 for H-Bridge ( watch out for counterfeits which are IR2103 https://www.tinytransistors.net/2021/03/14/fake-ir2104/ ! For counterfeits of IR2104 or when using IR2103 you need to short pin 2&3 and detach pin 3 from VCC on each IR210X chip! )
• 4 x 10 Ohm / 0.25W(or more) for H-Bridge drivers output ( between IR210X and MOSFET Gate pin)
• MOSFET transistors : 1 x IRF 4115 for single MOSFET solution OR for H-Bridge MOSFET solution : 4 x IRF510N or 4 x IRFZ24N or 4 x IRFZ44N, 4 x IR2104... You may even use the cheapest counterfeits from Aliexpress...
• Diodes : 2 ultrafast Schottky diodes UF4007 for Single MOSFET option, optional Zener diode 18V ( to protect MOSFET IRF4115 from electrostatic discharge (ESD) and overvoltage on Gate pin) and High power Schottky for single MOSFET solution
• H-Bridge MOSFET solution needs additional 2 x 1uF MLCC caps for IR210X chips
• Coils for single MOSFET solution - high current coils depending on availability : one 3.3 miliHenr coil per each 4 transducers OR one 4.7 miliHenr coil per each 5 transducers OR one 6.8 miliHenr coil per each 6 transducers, or single big coil 1mH / 10 Amp per each 20 transducers. Coils needs to be put IN PARALLEL to the parallel connected transducers here.
• Coils for H-Bridge solution - ONE coil 5uH - 22uH /10A conencted IN SERIES to the group of parallel connected 20+ transducers. If more transducers used, you need to DECREASE the inductance by unwinding wraps. This version needs some experimentation on number of wire wraps on the coil. Adjust it to get highest possible voltage on transducers. Unwind the wraps from the coil and periodically check the signal voltage with oscilloscope.

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See the video showing how this device works :

• Old version : https://www.youtube.com/watch?v=YBQ7A4W0bTo ( please do not use it , low jamming capability )
• New version for Arduino (and main4.c / main5.c for ATTINY) : https://youtu.be/JFtU2hQQ2vQ
• Re-created original version for Digispark : https://youtu.be/PcTkMWJb_Gs
• The newest version microphone jamming beast with TPA3116D2 audio amplifier board - jamms even iPhones : https://youtu.be/8RgoYlrgW4s
• The version that supports jamming iPhones is available here : https://youtu.be/nIupojN8bRk?si=n5qydTXHUljC6Rzw
• The version with MOSFET driver chip TC4420/IXDN614PI , MOSFET transistor IRF4115 and set of 4.7 MiliHenr coils : https://youtu.be/p5w_T1xVSF8
• 2 versions without AD9833 - single MOSFET+driver (working on older phones), full H-bridge 4 MOSFETs + 2 drivers (working on newer iPhones ) : https://youtu.be/84xKVirOIlM
• Jamming iPhone 17 example with H-Bridge jammer version : https://youtube.com/shorts/-bGY1aQV2Jw?si=C__vO6hbOhsY6oaD