Here is a wideband receiver, very sensitive, can detect the radio radiation at gigahertz megahertz. While it is interesting to locate transmitters in the CB or UHF range, it is especially useful for "disinfestation" office or home in case of doubt about the presence of spy microphones.
You probably came to tell some thing confidential to one of your closest friends and then to hear the story repeated by other people ... Or, you see ahead before making important decisions on a situation that you normally only know of a commercial or financial, for example, which was put in place without the knowledge of all, you have certainly given an advantage over your competition.
Looks like we listen
In such cases, you may be asked to find out how this could happen or what he could betray you.
Definitely would not have been betrayed by your friend or your employees or by the idea began to germinate in your head that you could possibly be monitored or spied upon.
All kinds of doubts are now installed in your mind ... And then one day, because the first flight there was a second and then others, doubts became certainty: someone has installed a microphone spy in your vicinity.
How to search micro spy
To get rid of this obsessive idea, you looked under your desk, behind cabinets and behind schedule ... but found nothing.
But you probably have not thought to look under the carpet, under carpet, electrical outlets or in the ceiling ...
Not talking about the air you would have had if someone entering your office, you saw look in such a posture!
That's when you said that seeking a spy microphone in an office, hidden behind any file in the false ceiling or elsewhere, it's like finding a needle in a haystack.
Besides, how sure a micro spy discovered and destroyed today will not be replaced by another tomorrow, to another place, forcing you to start your research time?
The solution is electronic
No. Search in this way really makes no sense because there are better, since, you also made use of electronics.
For electronics that bothers you, you can also protect. This is a weapon of attack in the hands of your enemies is also a weapon of defense between your own.
Such devices have existed for some time and represent the basic array of detection.
They are responsible not only disinfesting offices but also houses and apartments where it would be even more difficult to find a spy microphone, without having to dig under the bed or under the table in the dining room, behind the TV or on the phone ...
These devices are called "micro spy detectors" or "bug detectors" in America.
Just light one and see how behaves the galvanometer needle associated therewith. If the needle moves, this indicates that a transmitter is turned on somewhere.
Watch and listen
The product we offer, although it can be used for other things as we have said in the introduction, is primarily a detector of spies.
Therefore, in addition to an audible indicator (buzzer), it is equipped with a meter needle whose movements give a first indication of the received signal strength. Indeed, we must know that if the eye and ear are good allies, the eye has the advantage of being the most sensitive in the sense that it leaves less easily deceive the ear. For example: when an aberration volume by 5 percent may go unnoticed to the ear, an aberration of the same size does not go unnoticed to the eye.
Although the buzzer emits a note whose frequency varies with the RF field received by the antenna, the needle of the VU meter that provides valuable information more easily: they are small deviations of the needle allowing to finding the hidden transmitter.
A simple, seamless
Once it has detected the presence of an electromagnetic field, and after turning off all devices known capable of generating high frequency (mobile phones, radio transmitters or receivers), it remains only to move in all directions, ears attentive to the sound of the buzzer and eyes on the needle VU meter, until you find the direction in which correspondence is detected maximum intensity.
Then, pointing in that direction, always being guided by both the sound and the movements of the needle of the VU meter, you end circumscribing an area, and this is where to look the "bug" (you guessed it: the transmitter spy).
Being a spy microphones detector based on the quantification of an electromagnetic field, it should be noted that our apparatus is unable to detect the presence of micro phone (like "Infinity") most often hidden inside handsets, or directional microphones or laser.
Nevertheless, considering its use up to a sophisticated spy already high but not claiming to thwart sophisticated systems in the extreme, this kind of detector can be considered an infallible defense weapon.
Indeed, in general, we know that the systems most commonly used to intercept, without an office or room, the sound of a voice or sometimes even pictures, are based on emission radio.
This means that if a test with this detector does not reveal anything, you can be sure that the room complained there is no hidden transmitter.
Therefore, if your profession or because you're driven by momentary needs, you want it or need to make sure that in your home, your office, at home or at one of your friends or clients it does there is no micro spy installed, our installation is ideal.
Analysis Schema
Figure 1: Diagram of detector spy microphones. This is an economical and easy to make. Indeed, as can be seen by examining the diagram in Figure 1, it is simple, compact, essentially around an integrated circuit LM324 quad operational amplifier.
In general, a detector of spies should be able to locate transmitters operating in a very wide range of frequencies from a few megahertz up to gigahertz.
It is therefore a wideband receiver. To better understand how it works, analyze the schema floor by floor.
The first floor, one which is connected the antenna, is an amplifier / detector. The second floor is an amplifier, differential type, with a filter. The third stage is a frequency modulated oscillator. The top floor consists of an acoustic signal modulated by note.
Radio waves collected by a short antenna and converted into an electrical signal, passing through C6, the base of transistor T1.
The diodes D2 and D3 are used to limit the peaks of the incoming signal and bring it between 0.6 volts and 0.6 volts in order to avoid saturating the input transistor if we approached too near a powerful transmitter.
These diodes, called to work at frequencies of several hundred MHz models are necessarily fast. It is important not to replace them with slow switching models, because this second type of diodes, with their large internal capacity, lowered to the point where the input sensitivity of the detector that would be reduced to unacceptable values.
T1 amplifies the RF signal, just the value needed to carry out detection. This is done by the diode D1, too type fast switching. The detection is done by adjusting the signal-wave.
RC filter, formed by resistor R5 and capacitor C3, to retrieve the audio signal.
The detection principle is based on the property that diodes only pass current in one direction. In other words, depending on the variable voltage located at the foot of the receiving antenna is located, across the resistor R5, unidirectional pulses whose amplitude is directly proportional to the strength of the modulating signal. The latter can be either an analog signal (which is the case when dealing with a radio transmitter, a microphone spy, a walkie-talkie, etc..) Is a digital signal (remote control transmitters, modems paket , etc..).
The capacitor C3 is loaded with these unidirectional pulses, while the discharge resistor R5 soon.
Across this resistor R5, and there is a signal whose envelope is a pretty good replica of the tension that was used to modulate the transmitted RF signal.
In the case of an audio device, the signal is extracted represents the voices or sounds transmitted, while in the case of digital information, it leaves the form of pulses which, frankly, is rarely as perfectly square as you thought.
The next stage is an operational amplifier (U1A), which receives the signal detected via the resistor R3, and amplifies it in a ratio determined by the network against negative feedback formed by the resistors R1 and R2.
However it should be noted that the operational amplifier also receives on pin 2, the same RF signal produced by the first stage but not yet detected. Thus U1A is configured as a differential amplifier whose function is twofold: first, amplified as it should (about 200 times, since the signals from the antenna only measure only a dozen or even a hundred microvolts) part of the signal detected by D1 and, secondly, improve the quality of single-wave detection.
Once amplified, the LF signal is stripped of the HF component remaining in the capacitors C1 and C2 before reaching the input of another differential amplifier stage, namely the operational amplifier U1B.
Note that the leg 1 of this amp, in addition to being connected to the input of the operational amplifier following (U1c), is also connected to a small galvanometer needle (meter).
The latter, connected in series with a resistor (R20) whose role is to limit the current to a few hundred microamperes and prevent the needle from the device deviates too sharply to the left of the dial is alimentépar the detected signal at the output of the amplifier. Thus, it becomes a visual indicator of the received radio signal strength. And even more, because the deviations of the needle, not only provide an indication of field strength and thus the strength of the show, but also give some idea as to the modulation.
The second differential stage (U1B) is part of an oscillator controlled by the adjustable voltage output of the receiver.
At rest, that is to say in the absence of any RF signal, the oscillator produces a steady tone whose frequency is about 800 Hz
This note is amplified by the transistor T2, which excites the buzzer BZ1 makes audible.
When one is in the presence of a radio signal, the voltage coming out of the leg 1 of the operational amplifier changes in proportion the height of the note.
Thus, as the note becomes more or less acute, the user is informed of the importance of the RF field environment. The higher the score goes up in frequency, the higher the RF field environment is strong.
Conversely, the higher the field, the lower the note down in frequency, to reach the rest frequency. This means that we are moving away from the RF source.
The modulated oscillator, consisting of amplifiers U1B and U1c (two of the four operational amplifiers located in the integrated circuit U1), produces a square wave whose operation exploits the charge / discharge the capacitor C8.
Under the effect of the RF carrier to the antenna, the first of these two operational amplifiers, configured as a differential amplifier, receives two voltages vary slowly;
corresponding to the first demodulated signal which reaches the tab 13 through the single resistor R18, while the second one that reached the lug 12, is the same signal but this time attenuated by the voltage divider R16/R17.
The same thing occurs at rest, when in the absence of any signal BF the only potential bias is that the voltage divider R4/R5 requires an amplifier U1A.
Particularly studied in this way to interact both inputs of operational amplifier on one other fact, that initially, it tends to have the output low, since the potential present on the inverting input overrides the potential at the noninverting input.
Thus, the capacitor C8 is charging, and the output voltage on the tab 14 gradually decreases until it reaches the lower threshold.
Therefore, the operational amplifier configured as a window comparator is triggered. 8 paw from 0 volts to the high state, which closes to ground the resistor R21, thus causing saturation of transistor T3.
This causes a sudden lowering of tension on the leg 13 and, consequently, the levels are reversed.
So is the potential at the noninverting input which overrides the one on the inverting input and this voltage differential traces the level of output voltage, forcing the burden of C8 with reversed polarity, c ' that is to say the positive side of the output (pin 14).
However, the voltage does not rise indefinitely, because when it reaches the upper threshold, that is to say, the maximum threshold set by the window comparator U1c, it switches back and back to 0 on the voltage bracket 8.
The resistor R21 once seen this change and has the potential of transistor T3 ban.
The tension on the lug 13 may well start to rise and exceed the one on the lug 12.
As a result, the output of U1B begins to approach zero, and so on. Therefore, a cyclical phenomenon arises, which generates a sawtooth signal on the leg 14 of U1B and a rectangular signal at the output of U1c (leg 8).
The following buffer (U1D) configured in non-inverting amplifier with unity gain, amplifies the current rectangular pulses and sends them via the chemical C8 capacitor on the base of transistor T2 which acts as an amplifier, before attacking the pellet piezo buzzer BZ1. The latter can issue an audible note.
The portion of the audio signal fed back to the inverting input of U1B causes the change of starting potential of each ramp. Thus, it accelerates the change in voltage across C8, which determines an anticipation of the switching window comparator U1c and results in a gradual increase in the frequency of oscillation of the whole.
Conversely, the higher the voltage of the audio signal detected decreases, the frequency generated by oscillator modulated also decreases, because the starting potential of the ramp down a little at a time and each time it takes slightly longer time to switch U1c.
Figure 2: Schematic implementation of the components of detector spy microphones. 
Figure 3: Photograph of a prototype detector of our spies. 
Figure 4: Drawing scale 1, the circuit board needed to achieve. Component List
R1 = 1 MΩ
R2 = 4.7 kΩ
R3 = 1 kΩ
R4 = 4.7 kΩ
R5 = 1.5 kΩ
R6 = 470 Ω
R7 = 22 Ω
R8 = 39 kΩ
R9 = 100 kΩ
R10 = 10 kilohms
R11 = 100 kΩ
R12 = 10 kilohms
R13 = 1 kΩ
R14 = 10 kilohms
R15 = 10 kilohms
R16 = 47 kilohm
R17 = 1.8 kΩ
R18 = 100 kΩ
R19 = 10 kilohms
R20 = 47 kilohm
R21 = 47 kilohm
C1-C5 = 10 nF multilayer
C6 = 47 pF ceramic
C7 = 2.2 uF 16 V electrolytic
C8 = 10 nF multilayer
C9 = 100 uF 16 V electrolytic
D1 = Diode BAT85
D2 = 1N4148 diode
D3 = 1N4148 Diode
D4 = 1N4007 diode
U1 = LM324 Integrated
Q1 = NPN SOT23 BFR93 SMD
T2 = BC547 NPN
T3 = BC547 NPN
Buzzer BZ1 = without electronics
S1 = Switch
Miscellaneous:
1 Terminal 2 poles
1 Support 2 x 7-pin
1 telescopic antenna
1 Clip 9 Volt Battery
1 Housing Teko or equ.
4 adhesive plastic spacers
1 PCB ref. S370
Figure 5: Pinout top view, greatly enlarged, the transistor BFR93A version of CMS. The markings on his body should be turned upward and remain visible. 
Figure 6: Main characteristics of the transistor BFR93A. 
Figure 7: To make our detector capable to operate over a very wide band and thus be able to detect sources HF from megahertz to gigahertz, we used in the input circuit, a transistor specifically designed for very high frequencies. This is a BFR93A, NPN out plants Philips CMS version. This type of transistor can mount up to 6 GHz and, like most of his "brothers" designed for low power use in the field of very high frequencies, it works at low supply voltages and noise is 1.9 dB. In our scheme it is connected in common emitter configuration fairly standard for the input stages. This component should be handled with care. Avoid too much heat during soldering. Instructions detector
The way it was designed, this sensor is capable of signaling the presence of all sorts of spy microphones, including those of low power.
However, there are many factors that determine the effectiveness (the antenna, the point at which the microphone is hidden spyware, etc..).
Its use is very simple. Once turned on, in the absence of any RF signal, the buzzer emits a steady tone whose frequency is around 800 Hz
Under these conditions, the needle of the VU meter must remain motionless, completely at the zero position, or its close vicinity. If, by moving the detector in all directions, we find one which means a change in tone is the direction we need to move because, on its axis, there is indeed a light glowing .
Before making such a maneuver, it is obviously turning off all devices capable of emitting an electromagnetic field (cell phones, wireless sensors, remote controls, etc.).. Whenever you notice a change in tone of the buzzer sound and movement on the needle of the VU meter, you must be extra vigilant.
By guided by both the sound and the indications of the needle of the VU meter, you should come to identify the suspect area and find the micro spy (people in the art, in their jargon calls " bug ").
As some spy microphones are voice-activated type, that is to say, they emit only in the presence of a sound, it is good to make noise during the research.
Figure 8a. 
Figure 8b. Figure 8: Our prototype has been housed in a plastic case in which we have arranged the necessary openings in the light-meter at the power switch and the antenna (Figure 8a).
This will depend on availability. If you can not find a telescoping antenna like the one we used (Figure 8b), you can use an ordinary piece of enameled copper wire of about 20 16/10 inches long.
Ideally, to capture the spy microphones operating in the FM band, the antenna should be measured 75 centimeters. While capturing those operating in the UHF frequency of 400 MHz and beyond, we should use a shorter antenna, about 20 to 25 centimeters.
With an antenna of this length can still explore the range up to 1 GHz. The advantage of the telescopic antenna is still evident because it can lengthen or shorten depending on what you search.
The practical realization
Note straight away that this detector is a device specifically phones.
Held in the hand and walked in all the corners of a room, he would bear evil to be attached to a cable connected to a wall outlet! Moreover, its use is casual and power consumption limited to twenty milliamperes.
This is why its power is only through a 9-volt battery contacts to pressure in accordance with the requirements of the scheme (see "BATT").
It is good practice to use when connecting a wire to the red line "+" and black wire to one of the "-".
This has the advantage of avoiding all ambiguities and having to ask questions later.
Once in possession of the printed circuit, including a scale drawing is given in Figure 4, first mount resistors and diodes.
For the latter must ensure compliance with the polarities. To make it simpler and easier, we suggest you refer to the diagram board layout of Figure 2.
Then mount the bracket 2 x 7 feet for receiving the LM324 integrated circuit and should be steered correctly from the outset not to take the wrong direction during insertion of the circuit.
Then mount the two capacitors by chemical, again, note the polarity.
Then turn up the transistors.
There are three, but one of them deserves special attention.
These T1 (Figure 5) CMS version (surface mount device). Most of its technical characteristics are summarized in Figure 6.
For those of you who do not know yet, unlike what is done with conventional components for which holes are provided on the PCB for SMD there are no holes because they have no legs to speak of.
CMS can arise with a pair of tweezers (or tweezers fine point) on the tiny pellets (undrilled) provided on the PCB and solder side slopes (see enlarged detail in Figure 7).
On the body of the CMS, using a magnifying glass, you can read references.
The transistor must be placed so that after being welded, references are still apparent.
The collector is the middle electrode (Figure 5).
When it was the turn of the transistor, you do not solder the three electrodes in a row, but let cool each weld before moving to the next. Use for this, a soldering iron down very thin, with a power not exceeding 30 watts.
Melt the tin directly on the solder contacts and avoid the heat too long. You should keep the soldering iron on the transistor that only 3 to 4 seconds at most.
After you busy transistors, insert and solder the buzzer BZ1.
This is a piezo-electric regular free oscillator.
Insert the terminals for connecting two poles, one of the on / off switch and the other meter.
This will be a model 200 to 300 microamperes full scale. Attention to his sense of connection because it has polarity "+" and "-" to be absolutely respected. Refer again to the layout diagram of components and type shown on the meter.
Everything can be housed in a small plastic housing.
The antenna is based on availability.
If you do not have a telescoping antenna like the one we used in our prototype (Figure 8) you can use an ordinary piece of enameled copper wire rigid (16/10), about 20 centimeters long you directly connected to the circuit board through a hole in the casing.
Once editing is complete, checked and boxed, put the circuit. There is absolutely no adjustments to make.
The detector is ready to operate immediately. If you have a source generating the HF, you can immediately see how your detector spy microphones.
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