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    Here is a simple RF bug detector that will help you detect spy bugs and can operate up to 2 GHz. Below are some essential things required for this circuit:

    • to cover a large frequency band
    • make a sound during the detection
    • optical and acustical indication when near the bug
    • sensitivity not too high in order to accurately locate the rf bug
    • consume as little current from battery

    RF Bug Detector Schematic

    rf spy bug detector circuit schematic

    A1, A2, A3, A4 = 1 x LM358 or CRX423 (14 pin types)

    It can detect any RF waves with frequencies up to 2 GHz due to antenna circuitry and to input amplifier stage that is made of BFR91A transistor. The amplification is pretty high because of the way the base is polarised. The RF signal detection is made with a Schottky diode that has a low voltage on junction and is operating at a high frequency.

    Further, the obtained voltage is filtered and amplified with A1. Its value is enough to be displayed on the scale of a microammeter. A2 and A3 sections together with the other components form a voltage controlled oscillator. The sound is amplified by A4 section and then is applied to a 8Ω/0.5W speaker. Use a telescopic antenna that can retract to a small length (~10cm) and can extend up to 1 meter.

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    7 Responses to "RF Spy Bug Detector Circuit"

    1. You know that sometimes the window panes are used with a laser beam that is used to reflect the sound reflected undetectable! but this the reason why they have music near the window using the pane as your speaker?

      • Yes, I heard about it and I found a project here http://lucidscience.com/pro-laser%20spy%20device-1.aspx but it is not too sensitive and it is too hard to adjust.

      • sir…am very much interested in rf field…am trying for a mobile charger..build along with a mobile..(ie)this circuit will receive rf signals from environment for charging…so,please give me some suggestions for this and explain the disadvantages in it…

      • If I do understand you correctly you want to use this bug spotter to charge the battery of some sort. You need the following 1) live near a very high power transmitter radio station. 2) The power that can be obtained is very small and not worth the effort and illegal.The “Sniffer” use a battery itself. 3)Remember in this world there is no such thing as a “Free lunch”! During the 2nd world war some of the people that did live near a 100 Megawatt transmitter of the Third Reich They could get if I remember correctly, sufficient power to light a small fluorescent lamp with the correct antenna and that is a quarter wave length of the frequency The formula is 300Meg divided by the frequency and that answer divided by four and if you want to use mains that length will be several kilometers long !!I hope that this make sense for you as if this could be done then electricity companies will not be very happy !

    2. Hi Marian,

      Can you please include a complete and detailed parts bin for us beginners?

      Thank you!

    3. Hi,
      Could anyone, please, provide some detailed information about the antenna (material, size, construction details, etc.) and the microammeter (range, type, etc.) requirements

    4. Hi,the LM358 dusn’t exist as a 14 dil IC, so wath are connection numbers as you wanted to use 2 x LM358.

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