Almost every novice radio amateur has tried to assemble a radio bug. There are quite a few circuits on our website, many of which contain only one transistor, a coil and a harness - several resistors and capacitors. But even such a simple scheme will not be easy to configure correctly without special equipment. We won’t talk about the wave meter and HF frequency meter - as a rule, beginning radio amateurs have not yet acquired such complex and expensive devices, but assembling a simple HF detector is not just necessary, but absolutely necessary.
Below are the details for it.
This detector allows you to determine whether radiation is emitted high frequency, that is, whether the transmitter generates any signal. Of course, it will not show the frequency, but for this you can use a regular FM radio receiver.
The design of the RF detector can be any: wall-mounted or a small plastic box in which a dial indicator and other parts will fit, and the antenna (a piece of thick wire 5-10 cm) will be brought out. Capacitors can be used of any type; deviations in part ratings are permissible within a very wide range.
RF Radiation Detector Parts:
- Resistor 1-5 kilo-ohms;
- Capacitor 0.01-0.1 microfarad;
- Capacitor 30-100 picofarads;
- Diode D9, KD503 or GD504.
- Pointer microammeter for 50-100 microamps.
The indicator itself can be anything, even if it is for high current or voltage (voltmeter), just open the case and remove the shunt inside the device, turning it into a microammeter.
If you do not know the characteristics of the indicator, then to find out what current it is at, simply connect it to an ohmmeter first at a known value. known current(where the marking is indicated) and remember the percentage of scale deviation.
And then connect an unknown pointer device and by the deflection of the pointer it will become clear what current it is designed for. If a 50 µA indicator gives a complete deviation, and an unknown device at the same voltage gives a half deviation, then it is 100 µA.
For clarity, I assembled a surface-mounted RF signal detector and measured the radiation from a freshly assembled FM radio microphone.
When the transmitter circuit is powered from 2V (severely shrunken crown), the detector needle deviates by 10% of the scale. And with a fresh 9V battery - almost half.
This interesting device allows you to hear the world of electromagnetic radiation that surrounds us. It converts high-frequency vibrations of radiation generated by a variety of electronic devices into an audible form. You can use it near computers, tablets, mobile phones, etc. Thanks to it, you will be able to hear truly unique sounds created by operating electronics.
Schematic diagram
The scheme assumes the implementation of this effect with the smallest possible number of radioelements. Further improvements and corrections are at your discretion. Some part values you can tailor to your needs, others are permanent.
Build process
Assembly requires the use of a breadboard of at least 15 x 24 holes, and special attention refers to the arrangement of elements on it. The photographs show the recommended location of each of the radio elements and what connections to make between them. Jumpers on printed circuit board can be made from cable fragments or cut off legs from other elements (resistors, capacitors) that remained after their installation.
First you need to solder the coils L1 and L2. It's good to move them away from each other, which will give us space and increase the stereo effect. These coils are the key element of the circuit - they act like antennas that collect electromagnetic radiation from the environment.
After soldering the coils, you can install capacitors C1 and C2. Their capacitance is 2.2 μF and determines the lower cutoff frequency of sounds that will be heard in the headphones. The higher the capacitance value, the lower the sounds reproduced in the system. Most powerful electromagnetic noise lies at 50 Hz, so it makes sense to filter it out.
Next, we solder 1 kOhm resistors - R1 and R2. These resistors, together with R3 and R4 (390 kOhm), determine the gain of the operational amplifier in the circuit. Voltage inversion is not particularly important in our system.
The virtual mass is resistors R5 and R5 with a resistance of 100 kOhm. They are a simple voltage divider, which in this case will divide the 9 V voltage by half, so from a circuit point of view the m/s is powered by -4.5 V and +4.5 V in relation to the virtual ground.
You can install any operational amplifier with standard pins in the socket, for example OPA2134, NE5532, TL072 and others.
We connect the battery and headphones - now we can use this acoustic monitor to listen to electromagnetic fields. The battery can be glued to the board with tape.
Additional features
What can be added to increase functionality? Volume control - two potentiometers between the output from the circuit and the headphone jack. Power switch - now the circuit is on all the time until the battery is disconnected.
During testing, it turned out that the device is very sensitive to the field source. You can hear, for example, how the screen on your mobile phone is updated, or how beautifully the USB cable sings while transferring data. When attached to a switched-on loudspeaker, it works like a regular and quite accurate microphone that collects the electromagnetic field of the operating speaker coil.
A selection of diagrams and designs of homemade bug detectors for searching for radio bookmarks. Typically, radio eavesdropping circuits operate at frequencies in the range of 30...500 MHz and have a very low transmitter power of about 5 mW. Sometimes, the bug operates in standby mode and is activated only when noise appears in the controlled room.
This article discusses a bug detector circuit for searching for listening devices. The bug detector circuit is usually a bridge high-frequency voltage detector that operates over a huge frequency range.
Bug detector. Simple voltage detector circuit |
This simple circuit perfectly catches radio bugs, but only in the frequency range up to 500 MHz, which is a significant disadvantage. The tension detector antenna is made of a half-meter-long pin with a diameter of no more than 5 mm and insulated on the outside. Next, the signal is detected by a germanium diode VD1 and amplified by transistors VT1, VT2). The amplified UPT signal passes to a threshold device (DD1.1) and a sound generator made on elements DD1.2 - DD1.4, which is loaded onto a piezo emitter. As inductance L1, a low-frequency choke on a 2000NM ferrite ring is used, containing 200 turns of PEL 0.1 wire.
Another simple one homemade device to search for radio bookmarks, is shown in the diagram in the figure just above. This is a broadband high-frequency voltage bridge detector operating in the range from 1...200 MHz and makes it possible to find “bugs” at a distance of 0.5 to 1 m.
To increase sensitivity, a proven method of measuring small alternating voltages using a balanced diode-resistive bridge is used.
Diodes VD5, VD6 are designed to provide thermal stabilization of the circuit. Three-level comparators made on elements D1.2...D1.4 and LEDs are connected to their outputs, which are used as an indicator. Diodes VD1, VD2 are used as a 1.4 volt voltage stabilizer. Operating the device is not very easy and requires practical skills, since the circuit can react to some household appliances, televisions and computers.
In order to simplify the process of identifying radio tags, you can use replaceable antennas of different lengths, which will change the sensitivity of the circuit
When you turn on the device for the first time, you need to use resistor R2 to make LED HL3 glow. This will be the initial sensitivity level relative to the background. Then, if we bring the antenna closer to the radio signal source, other LEDs should light up depending on the amplitude level of the radio signal.
Resistor R9 adjusts the threshold sensitivity level of the comparators. The circuit is powered by a nine-volt battery until it discharges to 6 volts
Resistors R2 can be taken SPZ-36 or other multi-turn, R9 SPZ-19a, the rest are any; capacitors C1...C4 K10-17;.
You can also use any LEDs, but with low current consumption. The design of the circuit depends only on your imagination
During operation, any radio bug emits radio waves, which are detected by the detector antenna and enter the base of the first transistor through a high-frequency filter, which is made on capacitors C1, C2 and resistance R1.
The filtered signal is amplified by bipolar transistor VT1 and goes through capacitor C5 to the high-frequency first diode. Variable resistance R11 regulates the proportion of the signal on the diode entering the operational amplifier DD1.3. It has a high gain, which is set by C9, R13, R17.
If there is no signal from the radio tags at the antenna, then the signal level at the first output of the op-amp DD1.3 tends to zero. When radio emission occurs, the amplified signal from this output will reach the audio frequency generator voltage controlled, assembled on elements DD1.2., DD1.4 of the MC3403P microcircuit and a third transistor. From the output of the generator, the pulses are amplified by a second transistor and sent to the speaker.
Bug detector with ten LEDs |
The basis of the electromagnetic field detector is the LM3914 microcircuit, which has ten comparators internally and, accordingly, the same number of outputs for connecting LEDs. One of the outputs of each comparator is connected to the input through a signal amplifier, the other output is connected to a resistive divider at the point corresponding to the specified indication level.
The beginning and end of the resistive divider are connected to pins 4 and 6. The fourth is connected to the negative pole of the source in order to provide a voltage indication from zero. The sixth is connected to the 1.25 volt reference output. This connection means that the first LED will light up at a voltage level of 1.25 volts. Thus, the pitch between LEDs will be 0.125.
The circuit operates in the “Point” mode, that is, a certain voltage level corresponds to the glow of one LED. If this contact is connected to the positive of the power source, then the indication will be in the “Column” mode, the LED at the specified level will light up and everything below. By changing the value of R1 you can adjust the sensitivity of the detector. You can use a piece of copper wire as an antenna.
Hello, dear friends!
I purchased and tested the functionality of an electromagnetic radiation detector. I ask for a cozy cut :)
Let’s start from afar, I don’t watch TV myself, but when I’m visiting my parents I watch it with one eye, when I talk to my mother. So, by chance, my mother and I watched a piece of a program in which the film crew of the NTV channel “Mysterious Russia” ran to a cemetery with an electromagnetic radiation detector.
The announcer, in a sepulchral voice, said: “Today it is reliably known that increased electromagnetic background can actually negatively affect people. Push them into rash, risky actions and even suicide.” Well, and so on, I don’t remember if they caught ghosts there or anything else, it doesn’t matter now.
I thought it would be a good idea to measure the radiation in the server room, besides, my mother also wanted one. High-voltage power lines inspire horror in many people, or rather the proximity of their residence.
I read on the Internet that there are household sensors for detecting “harmful electromagnetic fields that come from high-voltage lines, television screens, computers, microwave ovens, etc. Experts believe that, starting at a level of 2-3mG, these electromagnetic fields increase the danger of certain diseases (for example, cancer)."
There is a video about such a device, although the price is 2000 rubles, who is too lazy to look for it, here is the link
There is also one for 140,420 rubles, here, but this is for gourmets :)
I sat and looked for Chinese analogues in online stores and came across this copy.
I talked with the seller, begged for a discount as always, this time they gave 20% as for the “first order in your store.”
I paid $13, they sent it and gave me a track. I waited 24 days, here is the track.
The parcel was well packed, sealed, the device was in a separate box, the box was in excellent condition, there was no battery included, this is my own:
I quickly inserted the battery:
I checked the functionality, it beeped and showed numbers on the screen when brought to power cables And household appliances, everything is in order, the device is working. The controls are very simple: the first red button is to turn on, the second is to freeze the value on the screen.
Almost immediately I decided to take it apart:
I was somewhat confused by the crumpled antenna inside, so I immediately decided to straighten it and run it along the body, making small slits with a stationery knife (as it later turned out, this was not superfluous, because the sensitivity increased significantly):
It is not entirely clear in what units the device measures the electromagnetic field strength, presumably in milligauss (mG). It’s difficult to say for sure, since the device is not certified in Russia and it will not be possible to use it to legally assess the suitability of places of work (it can only be done illegally:)
I measured the voltage near the “high-voltage lines”, the device goes off scale and beeps furiously, but when moving 10 meters away from the line, it quiets down and shows 0. This made my mother very happy, since the house is located far beyond the border of these 10 meters. Although a reinforced concrete 220/380 V power line support with porcelain linear insulators can hardly be called high-voltage.
There are plans to visit my grandfather and measure the background of “harmful fields” in the apartment that interfere with his sleep.
Cons:
1) No certification in Russia
Pros:
1) Compact size
2) Low price
3) Light weight
This is my first review of such a complex thing. Please don't kick the techies too hard in the face :)
P.S.
I recorded a video of the sensor working without human hands.
Ultrahigh frequency (UHF) radiation or so-called microwave radiation has an adverse effect on the human body. To protect yourself and your loved ones from the consequences of this type of radiation, detectors of varying complexity are used to detect the leakage of radiation from microwave ovens, cell phones and other devices. How to identify a dangerous device — We’ll talk about this in this article.
Photo. 1. Household appearance microwave oven Panasonic
Not everything is what is written in the instruction manual household appliances(especially for translated manuals) is true. Most often, this is a so-called half-truth: on one side everything seems to be true, but it often turns out that something is left unsaid. The same applies to phenomena and processes that can be dangerous to the life and health of a person or his things.
Not so long ago, the time has passed (or maybe not yet) when portable household dosimeters were extremely popular among the population. No, of course, not every family had an apartment, country house nuclear reactor, but the products and those things that were bought from hand and in markets clearly required control. No, no, and the dosimeter went off scale... For the same reason, today people buy devices to measure the level of pesticides in various fruits of nature.
One of the sources adverse effects The human body is exposed to ultrahigh frequency (UHF) radiation or so-called microwave radiation. A striking example electronic device with a microwave radiation generator (magnetron) is a microwave oven (see Fig. 1).
In addition to potentially dangerous microwave radiation for humans and animals, a microwave oven (hereinafter referred to as the oven) creates strong electromagnetic radiation, which has a negative effect on some objects and things - for example, wristwatches with an electromagnetic system (and others).
Photo. 2. Panasonic microwave oven with the housing cover removed
Generally, a new oven will operate reliably and will not emit harmful radiation outside its housing, but it is still best to avoid placing watches, cell phones, or other items on it.
Stove that was being repaired outside service center, in which the main element of the generator - the magnetron - was replaced, with a damaged housing or having damage to the working chamber, waveguide and other deficiencies, is potentially hazardous to health.
To identify such harmful ovens and other devices (for example, a broken mobile phone), microwave radiation indicators are used. The simplest diagram of such an indicator is shown in photo 3.
Photo 3. Simple scheme microwave radiation indicator, which you can assemble yourself
Note to photo 3. A loop is a piece of copper wire with a diameter of 1...1.5 mm. Electric spot welding wire is quite suitable for this purpose. Microwave diode - diode type 2A202A, DK-V8 or similar. The tester is a milliammeter with a full needle deflection current of 100 µA. In our case, it is better to use a pointer device, for example, Ts4342, Ts4317 or similar. Non-polar capacitor - any, for example, MBM type.
The junction of the magnetron with the power source contains transition capacitors, which (together with the chokes) form a filter to protect against the penetration of microwave radiation from the magnetron and the waveguide to the outside.
The principle of checking a microwave oven is simple - a “loop” with a microammeter is slowly passed next to the body of the microwave oven (at a distance of 1-6 cm from it). A slow “scanning” speed is needed in order to capture microwave radiation in the most dangerous area of the oven.
The microwave radiation generator is turned on in the oven during cooking not constantly, but periodically. This is also noticeable visually: the backlight inside the oven’s working chamber dims a little, and the oven makes a little more noise when the generator is turned on.
What don't we know about the magnetron?
The most important component of a microwave oven is a magnetron, which is an electric vacuum diode designed to generate microwave oscillations. When the magnetron operates, power is released, which turns into heat, so a thermal electromagnetic field is created inside the working chamber. The power generated by the magnetron is supplied through a waveguide - a device that transmits energy to the working area of the furnace, which is a rectangular chamber (working chamber).
Photo 4. Close-up magnetron
Next to the waveguide output there is a rotating table on which the product to be processed is placed. All this is located inside the furnace body.
It is important that the radiation (hazardous to life if directly exposed to a person) does not extend beyond the furnace body. The furnace body is a closed metal structure, which at the same time serves as a screen for microwave radiation.
For household heat treatment in the microwave wave range, electromagnetic oscillations are used at frequencies of 2375, 2450 MHz - in very old models, and up to 10-12 GHz in modern ovens. In table 1 provides information on the depth of penetration of an electromagnetic wave (with energy losses) into some of the dielectrics.
Table 1. Penetration depth of an electromagnetic wave in a dielectric with losses at a temperature of 20-25 ºС
Modern magnetrons (magnetrons with a non-heated field cathode type MI and similar) provide “instant” (from the first pulse) readiness to operate at full power without wasting energy on heating the cathode, which significantly increases the reliability of the magnetron.
The use of a non-heated magnetron made it possible to simplify electrical diagram ovens, excluding dozens of radio components. In this regard, there is no need for a transformer, a control device and a voltage regulator in the magnetron filament circuit (since there is no filament itself), master and blocking generators, it was possible to reduce the weight and dimensions of the furnace, reduce the cost of the product, while simultaneously increasing its operational reliability.
Possible malfunctions of magnetrons:
The anode of the magnetron is made in the form of a copper cylinder. The operating voltage of the magnetron anode (depending on the type) ranges from 3800 to 4000 V. Power from 500 to 1200 W. The magnetron is mounted directly on the waveguide (Fig. 3). In furnaces where the manufacturer places a magnetron with a short waveguide, a defect such as breakdown of the mica gasket can be observed. This happens as a result of contamination of the gasket;
when the gasket breaks down, the magnetron cap melts (this happens with magnetrons of the type 2M-218N(R), OM7S(20), 2M213-09F, 2M-219N(V), 2M226-09F and structurally similar). It (the cap) can be replaced with a similar cap from another magnetron;
Like any lamp, it can lose its emission, resulting in a significant reduction in energy output and an increase in cooking time. Usually average term magnetron service life (for example, 2M213-xx) has a limit of 15,000 hours. Its efficiency is 75-80%, which is an effective indicator for magnetrons of microwave oscillation generators;
breakdown of transition capacitors can be detected using a tester in resistance measurement mode. The breakdown occurs on the magnetron housing. The malfunction is eliminated by replacing the entire assembly.
Separately, the magnetron can be checked only by generating all the voltages necessary for its operation.
Photo 5. Microwave oven power supply
In a microwave oven, the second most important element after the magnetron is the power supply (Photo 5). The entire safe operation of the furnace depends on its reliability.
A wonderful tool for repairing and diagnosing microwave ovens, in particular when diagnosing magnetrons, are current clamps, for example, ECT-650 “Escort”.
They allow you to measure the current consumed by the furnace, the current of the high-voltage winding of the transformer. The rated current consumed by the furnace is 4.5 - 6 A, the current of the high-voltage winding of the transformer is 0.3 - 0.5 A.
Large deviations from the specified values (especially in the direction of increasing individual parameters) indicate a local malfunction of the magnetron.
At the same time, an underestimation of all parameters can be explained by poor contacts, starting from the power socket and ending with switching elements (relays, electrical microswitches, contacts).
In order to make sure that the magnetron is working properly and that there is a sufficient level of microwave radiation inside the furnace body, it is checked with a detector.
Microwave Radiation Detectors
Photo 6 shows an industrial microwave radiation detector, which can be purchased at electrical goods stores.
Rice. 6. Microwave radiation detector
This device detects only microwave pulses, which can be checked by bringing the device directly to its walls while the oven is operating. It will also be useful for searching for “bugs” operating at ultra-high frequencies, searching for cell phones and checking their operation. Such an industrial tester costs less than 500 rubles.
The device is powered by a 6F22 Krona battery with a voltage of 9 V. The current consumption of the device in standby mode is a few μA, so the battery lasts a long time. An indicator LED is located at the top of the case.
It will light up when microwave radiation is present in the detector area (shown on the body by an arrow). The device does not measure radiation power, but records its presence.
Using such a detector, you can check not only the working chambers of microwave ovens and the presence of harmful radiation outside their housing, but also the presence of radiation from cell phones. It's easy to do.
It is necessary to bring the detector to a possible source of radiation, for example, to the body of a mobile phone at a distance of 2-10 cm. When the cell phone is active: during an incoming and outgoing call, unauthorized “communication” of the cell phone with the base station, when registering the cell phone on the network (for example, when turning on the cell phone) and in other cases - the detector indicator will show the presence of microwave radiation.
This visual lesson would not hurt to use in physics lessons in schools, so that people understand how harmful or useful it is to constantly carry a cell phone close to your own body (on your chest, on your belt, in your pocket, especially your chest).
The results of harmful microwave radiation (especially with constant exposure) are probably better commented on by scientists and medical professionals. On my own behalf, I will only add that microwave radiation is like an atom, which can be peaceful or not. This must be clearly understood when using a seemingly harmless mobile phone or microwave oven.
Another industrial device intended for motorists, called a “spark indicator,” can also be used as a microwave radiation detector. Such devices are commercially available, one of which is shown in Fig. 7.
Rice. 7. Photo ( appearance) microwave radiation detector — spark indicator
The device is designed to test high-voltage ignition circuits of cars. A sensor is installed inside the case (the same loop as in the diagram in Fig. 5, only in miniature), which, as practice has shown, responds not only to high impulse voltage in the ignition of a car, but also in the microwave radiation of a microwave oven and a cell phone.
A red LED located near the “high voltage” arrow also serves as an indicator of microwave radiation.
On remote wires, the indicator is powered from any power source with a constant voltage of 8-15 V, including a Krona battery or a car battery.
The peculiarity of the device is that it has sensitivity adjustment (the adjustment knob is located on top part body). Such a device costs around 300 rubles. Having it, you no longer have to worry about other microwave radiation detectors.
Safe work measures during repair and maintenance of microwave ovens
Failure to follow these rules may result in failure electric shock, injuries and failure of quite expensive components of the microwave installation.The most dangerous (of all available in domestic conditions) for humans is AC frequency 50 Hz, as well as microwave radiation.
A microwave oven connected to a 220 V network (under voltage) can be repaired and checked only in cases where it is impossible to perform work in a device disconnected from the network (setup, adjustment, measuring modes, searching for bad contacts in the form of “cold soldering” and similar cases).
Care must be taken to avoid exposure to dangerous voltage.Avoid burns from heating elements.
In all cases of working with the oven turned on, it is necessary to use tools with insulated handles. You should work with one hand, wearing long sleeves or oversleeves.
At this time, you must not touch the stove body or other grounded objects (central heating pipes, water supply) with your other hand. Wires measuring instruments must end with probes and have good insulation.
This general rules electrical safety.
Attention, dangerous:
soldering of furnace elements under voltage;
repair the stove included in electrical network, in a damp room, or with a cement or other conductive floor;
is located near the installation by persons not repairing it;
Like any source of microwave radiation, direct exposure to magnetron radiation can cause eye damage or skin burns. The human eye cannot see microwave radiation;
When replacing the magnetron, be especially careful. Do not leave installation debris in the waveguide;
Before replacing, always dilute the capacitor in the magnetron power supply circuit with a piece of insulated wire (the shunt resistor sometimes fails).
In addition, when operating the stove it is not allowed:
turn on the oven with the door or screen open (it will not turn on itself, since there is protection for that, but this point is relevant for those who neglect this protection by turning it off);
you can’t make holes in the body (housewives who dream of hanging the stove on the wall like a bread box, let such thoughts be abandoned).