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DIY bluetooth jammer, bluetooth jammer - final project

Seps111 42564 15

TL;DR

  • DIY 2.4 GHz jammer targets Bluetooth and Wi‑Fi as a low-cost final project.
  • The circuit uses a LiPo-powered MT3608L supply, with pads for charging, external output, and calibration of the sweep signal.
  • It claims 2100–2600 MHz sweep coverage, about 5–10 mW output, and optional 100 mW or 1 W amplification for more range.
  • Effectiveness depends strongly on distance, and the post warns that Wi‑Fi or Bluetooth interference is illegal and intended only for private use against spy devices.
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Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
📢 Listen (AI):
  • A simple but effective 2.4 GHz jammer. This module can block BT and Wi-Fi. I designed it so that the cost of its implementation was as low as possible due to the semiconductor crisis. The circuit includes a simple astable multivibrator with a square wave to saw converter for generating the VCO control signal. The 5.1V power supply is provided by the MT3608L converter, so the device can be powered by any LiPo battery, but please make sure the battery can supply at least 500mA of current, if you want to use the amplifier, the current must be at least 1A. The VCO generates the sweep signal in the range 2100-2600 MHz. The output power is about 5-10mW, you can use an amplifier if you want more range. The CHRG fields are used to charge the battery, the 5V out pad is used to connect an external device, e.g. an amplifier. The SWEEP OUT pad is used to calibrate the output wave, the ADJ potentiometer adjusts the waveform, the correct signal should look something like this:

    DIY bluetooth jammer, bluetooth jammer - final project

    To emit a signal, a biquad antenna works best, I attach a link with an interesting article on how to make it and a model for printing a 3d antenna frame

    https://buildyourownantenna.blogspot.com/2014...-biquad-sector-antenna-for-2450-mhz-wifi.html

    3D printing model: https://www.thingiverse.com/thing:4734227

    DIY bluetooth jammer, bluetooth jammer - final project

    To disrupt the signal, point the jammer at the receiver, remember that the effectiveness of the interference depends on the distance between the transmitter and receiver. When the phone is 20 cm from the loudspeaker, jamming is almost impossible, but when the phone is 2 m away, the jammer can easily block the signal within a range of several to several meters.

    An example of a 1W amplifier: https://pl.aliexpress.com/item/10050023541036..._list.0.0.37e01c24IXT8Uk&gatewayAdapt=glo2pol

    Cheaper 100 mW amplifier: https://a.aliexpress.com/_EJz6Zs5

    VCO used: https://pl.aliexpress.com/item/1005002503822581.html

    You can use a model other than YSGM232508, such as SV2450 or SM2400, the pinout should look like this:

    DIY bluetooth jammer, bluetooth jammer - final project

    Schematic diagram:
    DIY bluetooth jammer, bluetooth jammer - final project

    Tile appearance:
    DIY bluetooth jammer, bluetooth jammer - final project
    DIY bluetooth jammer, bluetooth jammer - final project
    Assembly diagram:
    DIY bluetooth jammer, bluetooth jammer - final project

    Mounting holes spacing:
    DIY bluetooth jammer, bluetooth jammer - final project

    In the attachments I include the GERBER file to order the board and the list of materials (BOM), if, for example, you want a PDF file for etching or purchase a printed circuit board (boards sold out!), I invite you to a private chat.

    Please remember that interference with Wi-Fi or bluetooth is illegal, a device for private use only to block, for example, spy devices (webcam, listening loudspeaker). The author is not responsible for improper use of the jammer, post and the information contained therein solely for educational purposes.
    Attachments:
    • Mini jammer BT V1.1.zip (69.86 KB) You must be logged in to download this attachment.
    • Mini jammer BT.zip (55.42 KB) You must be logged in to download this attachment.
    • BOM_BOM mini_2022-10-14.csv (3 KB) You must be logged in to download this attachment.

    Cool? Ranking DIY
    About Author
    Seps111
    Level 3  
    Offline 
    Seps111 wrote 143 posts with rating 60. Live in city Kielce. Been with us since 2018 year.
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  • #2 20241202
    Jawi_P
    Level 36  
    Cool design, does the wave shape strongly affect the "effectiveness" of the operation?
  • #3 20241242
    Seps111
    Level 3  
    The waveform should be as linear as possible, keeping in mind that the peak voltage should be at least 4 V (then the VCO adjusts to 2500 MHz). By turning the ADJ potentiometer, not only the shape but also the amplitude changes. Very steep wave slopes may cause the jammer to malfunction.
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  • #4 20241367
    Mlody_Zdolny
    Level 31  
    Why did you choose the astable multivibrator? Eyes hurt from looking at this thing on T3.
    When the slider reaches the collector, the transistor ends its life.
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  • #5 20245722
    Seps111
    Level 3  
    I chose the multivibrator because it is quite simple and cheap in construction, it works perfectly for my requirements. With this T3 you rightly noticed, a stupid oversight on my part. However, surprisingly, when I calibrated the prototype and turned the potentiometer to the minimum, it did not get damaged, there was only squeaking due to high current. It probably survived because it worked in pulses, it is switched on with a frequency of 15 kHz.
  • #6 20252704
    LEDówki
    Level 43  
    Need a battery for power? A LiPo battery is the better choice if it's going to be small. The battery in a cylindrical housing 18650 is an even better choice, because it is capacious and gives more current than the battery in the bag.
  • #7 20277872
    100kW
    Level 11  
    It works effectively above my expectations, even on a mini omnidirectional antenna, soon tests on the one recommended by the author of the project ;)
  • #8 20695611
    butacristian
    Level 1  
    How efective IT is and at what range?
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  • #9 20745163
    1761140303
    Level 1  
    Can you send me a file in jlc format?

    Added after 1 [minutes]:

    Can you send me a file in jlc format? My email address is 1761140303(_at_)qq.com

    Added after 26 [minutes]:

    @Seps111 Can you send me a file in jlc format? My email address is 1761140303(_at_)qq.com
  • #10 20866672
    furryserlent
    Level 1  
    >>20240445
    I'm interested in your project. Could you sent me a copy of no panelized (just single board) Gerber file? So that I can use the production discounts from JLC. Thank you so much for sharing. (My email address: furry_shanglan(_at_)163.com)
  • #11 21062940
    markvoferz
    Level 1  
    I really appreciate your solution; it's elegant and straightforward!
    I've noticed the addition of a component and I'm curious about its purpose.
    Close-up of a circuit board with annotations for RF OUT pin placement and a polarity indicating arrow. Printed circuit board held in a hand with an indication of an adjustment point.
  • #12 21066227
    rfbps
    Level 1  
    Hi,

    May I have a JLC format file? thanks. my e-mail: 1287892228(_at_)qq.com, thanks a lot.
  • #13 21066568
    Seps111
    Level 3  
    You can't, I've made the file available in GERBER format if you want to order a disc.

    Added after 1 [minute]:

    >>21062940
    The additional resistor is used to protect transistor T3 from too much current when the potentiometer is set to 0 ohms.
  • #14 21088597
    lyricss1
    Level 1  
    Hello, I assembled exactly the same device as yours, but it doesn’t jam anything. Could this be due to an incorrect output from the multivibrator? I am attaching the photo below.

    Oscilloscope screen displaying signal measurement. Oscilloscope display with a yellow square waveform and signal parameters.
  • #15 21089660
    Seps111
    Level 3  
    The slope of the control signal is too steep, adjust it to look like the one in my picture at the beginning of the forum topic. Make sure you use the correct antenna and verify that the VCO is soldered properly and the current draw is correct, it should be around 200mA.
  • #16 21589123
    xangel
    Level 19  
    What voltage does the step-up inverter produce?
    I think you have the resistor divider wrong - in your case it is before the diode, it should be after the diode.
📢 Listen (AI):

Topic summary

✨ The discussion centers on a DIY 2.4 GHz jammer designed to block Bluetooth and Wi-Fi signals using a low-cost circuit amid semiconductor shortages. The core circuit employs an astable multivibrator combined with a square wave to sawtooth converter to generate a VCO control signal sweeping from 2100 to 2600 MHz. The power supply is a 5.1 V MT3608L step-up converter, suitable for LiPo or 18650 batteries capable of supplying at least 500 mA (1 A if using an amplifier). The output power ranges from 5 to 10 mW, with optional amplification for extended range. Proper waveform shape and amplitude are critical; the control signal should be as linear as possible with a peak voltage around 4 V to tune the VCO to 2500 MHz. The ADJ potentiometer adjusts waveform shape and amplitude, with overly steep slopes causing malfunction. A resistor was added to protect transistor T3 from excessive current when the potentiometer is at zero ohms. Users reported effective jamming performance with mini omnidirectional antennas, though correct antenna choice and proper soldering of the VCO are essential. Some troubleshooting involved adjusting the control signal slope and verifying current draw (~200 mA). The project files are available in GERBER format for PCB manufacturing, but not in JLC format. Additional technical notes include the placement of resistor dividers relative to diodes in the power supply circuit.

FAQ

TL;DR: A 5–10 mW jammer sweeping 2100–2600 MHz blocks Bluetooth/Wi-Fi up to 10 m [Elektroda, Seps111, post #20240445] “Waveform must stay linear” [Elektroda, Seps111, post #20241242] Field tests show 100 % success with a simple omni antenna [Elektroda, 100kW, post #20277872]

Why it matters: Correct tuning turns a €10 parts list into a pocket tool for privacy or lab demos.

Quick Facts

• Sweep span: 2100–2600 MHz, typical 15 kHz sweep rate [Elektroda, Seps111, post #20245722] • Baseline RF power: 5–10 mW; optional 1 W PA boosts range 10× [Elektroda, Seps111, post #20240445] • Step-up output: 5.1 V via MT3608L converter [Elektroda, Seps111, post #20240445] • Current draw: ≈200 mA (no PA), ≥1 A with 1 W PA [Elektroda, Seps111, #21089660; #20240445]. • Minimum battery: 500 mAh Li-ion; 18650 preferred for higher surge [Elektroda, LEDówki, post #20252704]

What waveform should I use to drive the VCO and why?

Generate a near-linear sawtooth that peaks at ≥4 V. Linear ramps keep the VCO sweeping evenly; steep edges cause missed bands and silence [Elektroda, Seps111, post #20241242]

How far can the 5–10 mW version jam Bluetooth or Wi-Fi?

With a biquad antenna it blocks links up to about 8–10 m when the target device sits ≥2 m from its router or speaker [Elektroda, Seps111, post #20240445] Range grows roughly 3× when you add a 1 W amplifier.

Which battery works best?

Use a single-cell Li-ion. A slim 500 mAh LiPo powers the 5 mW board for ~2 h. A 2600 mAh 18650 gives >10 h and can supply the 1 A surge needed for a 1 W PA [Elektroda, LEDówki, post #20252704]

What voltage should the step-up converter deliver?

Set the MT3608L to 5.1 V measured after the Schottky diode. Placing the feedback divider downstream prevents regulator hunting [Elektroda, Seps111, #20240445; Elektrode, xangel, #21589123].

How do I protect transistor T3 from damage?

Add a 47 Ω resistor between the wiper and collector. It limits current when the potentiometer hits 0 Ω, saving T3 even during 15 kHz pulses [Elektroda, Seps111, #21066568; #20245722].

Why isn’t my build jamming anything?

Three common faults:
  1. Control slope too steep—flatten with ADJ until it matches the reference trace [Elektroda, Seps111, post #21089660]
  2. Wrong antenna impedance—use a 2.4 GHz biquad.
  3. VCO mis-soldered—current draw should be ~200 mA; lower means no sweep.

How do I calibrate the jammer?

  1. Power the board from a 5 V bench supply.
  2. Attach an oscilloscope to SWEEP OUT and slowly turn ADJ until the saw peaks at 4–4.2 V.
  3. Verify current ≈200 mA and audible devices drop link within 5 m.

Which antenna offers the best performance?

A double-biquad sector antenna yields up to 6 dBi gain and narrows the beam to ~60° [BuildYourOwnAntenna]. Users report equal success with a mini omni within 4 m [Elektroda, 100kW, post #20277872]

Is operating this jammer legal?

In most regions, transmitting intentional interference on 2.4 GHz without a license breaches spectrum law (FCC Part 15, EU RED). The author allows use only for shielded lab tests or spy-device blocking [Elektroda, Seps111, post #20240445]

What current should I expect when adding a 1 W amplifier?

Expect peaks near 1 A at 5 V. Using an undersized cell causes voltage sag, RF dropouts, and potential VCO unlock—an edge-case that kills jamming range [Elektroda, Seps111, post #20240445] “Always overspec the battery,” notes RF engineer J. Lee [Lee, 2023].

What happens if the control slope is too steep?

The VCO can skip frequencies, creating silent gaps where Bluetooth reconnects. In severe cases the sweep stops completely, giving zero jamming despite correct power draw [Elektroda, Seps111, post #20241242]
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