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This is a spy device that is really small and can be hidden any were it is a transmitter and your mobile is the reciver. This is a very small radio transmitter and can transmitt aduio signals up to a radius of 100 m.
For recording I recommend you to use an android phone as it has a wide band range .
They transmit on the FM band in the range 88MHz to 108MHz. It can be adjusted to transmit above or below the band and you need a radio that will pick up these frequencies, to detect them.
Since the FM band is almost entirely filled with radio stations, we will be providing details on how to adjust a radio so it will scan EITHER above the band or below the band. Most radios can only be adjusted 10MHz above or below but this will be enough to provide a "blank" space for your transmitter.
FM transmission provides perfect quality and when one of these transmitters is used in a house and received on a good quality radio, you cannot tell if the person is actually talking in the next room or via an FM link, through a radio.
If you think of this project is cool vote for me in the contest.

Step 1: Parts

1)Transistor- BC547
2)Electret mix
3)Resistor 330r,4.7k
4)Capacitor 4p7, 22n
5)10-40preset

For the coil use a 24 gauge coil and wind it over a thin pen.
Additional parts required to build a field strength detector to test if the bug is working.

Step 2: Final Step

Use a heatsink to enclose the circuit mount this on a 9v battery clip. Tune over the radio till u get an aduio output on your mobile. For best result use android phones. This circuit provides a clear audio output before testing it on a android use a high signal radio to find the perfect band tune the presets to get a required band as almost the entire fm band is filed with stations. For the antenna use a small 5cm copper wire . This whole circuit cane also be soldered board less on to a 9v battery clip. But use the heat sink to keep the circuit in one piece . If you don't get a signal check for the connections try changing the coil .

Step 3: Field Strength Meter

After making a transmitter, you will want to know if it is transmitting. In the case above, the circuit will only produce a carrier and this will be heard on the radio as a "quiet spot."
Rather than chasing up and down the dial, I made a piece of test equipment to let you know the bug is transmitting and the approx frequency of transmission.
It is called FIELD STRENGTH METER MkII.
The photo below shows the Field Strength Meter near the bug. The plastic knob on the trimmer allows adjustment without affecting the detecting circuit. Simply turn the knob (with the two antennas near each other) and the 3 LEDs on the project will illuminate.
Visit my instructable to get details on how to build a field strength meter.
https://www.instructables.com/id/FIELD-STRENGTH-METER/
<p>nice.</p>
<p>Superb work.</p>
<p>Nice spy Audio instrument.</p>
<p>Nice instrument.</p>
<p>great job.</p>
<p>nice job like this.</p>
<p>great one.</p>
<p>Nice Work Great Job sir.</p>
<p>This is awesome</p>
<p>nice work.</p>
<p>great work..</p>
<p>loving it..</p>
<p>i love with your job</p>
<p>good one;</p>
<p>great lightwieght and effective</p>
<p>Well done for such good quality using only 48K</p>
<p>can you put up links to get the materials required as well.. Thank you in advance</p>
<p>I don't see anything!!!!!</p>
<p>great lightwieght and effective</p>
<p>what is the size of this</p>
<p>what is the size of this</p>
<p>useful stuff :)!!!!</p>
<p>useful information !!!!!!!!!</p>
<p>useful stuff</p>
<p>loving thiss</p>
<p>nice ++</p>
<p>i want the circuit design</p>
<p>This is really coll! Would something similar for video work as well?</p><p>Very nice! :)</p>
<p>This is really coll! Would something similar for video work as well?</p><p>Very nice! :)</p>
you mean when there are two parties are talking to each other, we can hear their speech using this Spy Audio, or what ? <br>kindly explain
Whats a 4p7 capacitor ?
4p7 is an abbreviation for 4.7pF
Hello, <br>It seems that you have copied all your photos from here: <br>http://www.talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-1.html <br> <br> <br>And you got the photo's from the field strength meter from the same site: <br>http://www.talkingelectronics.com/projects/FieldStrengthMeterMkll/FieldStrengthII.html
Nice catch. It all seems to be pretty much copy and paste for both projects. <br>Sigh! This should probably be flagged for removal.
How long will this transmit for?
:) Nice
That's very compact and a neat job. I haven't seen better.
Aduio = Audio <br>Heatsink = Heatshrink
Looks like a cool idea and your results look great. That said, there really isn't enough information here for somebody like me to build this. Can you give more detail?
Agree, i would have voted for it had he put more work into the instructable.
hey i upgraded it you may want to check it out . And please vote for me it means lot to me.
This is better, I voted. Is the coil the part that is actually doing the transmitting? Can you explain how that works and how to adjust the signal?
The coil helps to detirmine the band width and experimenting with it will give you different signals , use the preset to get a desired band , with the help of the field strength meter.
sorry to here that I'm going to include some new stuff in this by end of today.
hey I included the parts list
hey I included the parts list
Could you include a detailed parts list? For example, what are the values of the resistors, caps, transistors, etc? Thanks!
hey im going to add a better version of this project by next two days.

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Bio: I'm a high school student like to build stuff, I have a lot to study at school so that's whys you may get ... More »
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