The group of electromagnetic waves is represented by numerous subspecies that have natural origin. This category also includes microwave radiation, which is also called microwave radiation. In short, this term is called the abbreviation microwave. The frequency range of these waves is located between infrared rays and radio waves. This type of irradiation cannot boast of a large extent. This figure varies from 1 mm to 30 cm maximum.
Primary sources of microwave radiation
Many scientists have tried to prove the negative effects of microwaves on humans in their experiments. But in their experiments they were guided by various sources such radiation is of artificial origin. And in real life people are surrounded by many natural objects that produce such radiation. With their help, man went through all stages of evolution and became what he is today.
With the development of modern technologies to sources of natural radiation, such as the Sun and others space objects, artificial ones joined. The most common among them are usually called:
- radar spectrum installations;
- radio navigation equipment;
- systems for satellite television;
- Cell phones;
- microwave ovens.
The principle of the effect of microwaves on the body
In the course of numerous experiments where the effects of microwaves on humans were studied, scientists found that such rays do not have ionizing effect.
Ionized molecules are defective particles of substances that lead to the initiation of chromosome mutation. Because of this, the cells become defective. Moreover, it is quite problematic to predict which organ will be affected.
Research on this topic has led scientists to the conclusion that when dangerous rays hit the tissues of the human body, they partially begin to absorb the incoming energy. Because of this, high-frequency currents are excited. With their help, the body heats up, which leads to increased blood circulation.
If the irradiation was in the nature of a local lesion, then heat removal from the heated areas can occur very quickly. If a person has fallen under the general flow of radiation, then he does not have such an opportunity. Due to this, the danger of exposure to rays increases several times.
Most main danger When microwave radiation influences a person, the reactions that occur in the body are considered irreversible. This is explained by the fact that blood circulation here acts as the main link in cooling the body. Since all organs are connected to each other by blood vessels, the thermal effect is very clearly expressed here. The most unprotected part of the body is the eye lens. At first it begins to gradually become cloudy. And with long-term irradiation, which is regular, the lens begins to collapse.
In addition to the lens, a high probability of serious damage remains in a number of other tissues, which contain a lot of liquid components. This category includes: 
- blood,
- lymph,
- mucous membrane of the digestive organs from the stomach to the intestines.
Even short-term but powerful radiation leads to the fact that a person will begin to experience a number of abnormalities such as:
- changes in the blood;
- problems with the thyroid gland;
- reducing the efficiency of metabolic processes in the body;
- problems with psychological state.
In the latter case, even depressive states are possible. Some patients who experienced radiation on themselves and at the same time had an unstable psyche even attempted suicide.
Another danger of these invisible rays is the cumulative effect. If initially the patient may not experience any discomfort even during the irradiation itself, after a while it will make itself felt. Due to the fact that on early stage It is difficult to trace any characteristic symptoms; patients often attribute their unhealthy state to general fatigue or accumulated stress. And at this time, various pathological conditions begin to form in them.
On initial stage the patient may experience standard headaches, as well as get tired quickly and have difficulty sleeping. He begins to develop stability problems blood pressure and even heart ache. But many people attribute even these alarming symptoms to constant stress due to work or difficulties in family life.
Regular and prolonged irradiation begins to destroy the body at a deep level. Because of this, high-frequency radiation was considered dangerous to living organisms. Studies have shown that a young body is more susceptible to negative influences electromagnetic field. This is explained by the fact that children have not yet had time to form reliable immunity for at least partial protection from negative external influences.
Signs of exposure and stages of its development
First of all, from such influence various neurological disorders. It can be: 
- increased fatigue,
- decreased labor productivity,
- headache,
- dizziness,
- drowsiness or vice versa – insomnia,
- irritability,
- weakness and lethargy,
- profuse sweating,
- memory problems
- feeling of a rush to the head.
Microwave radiation affects humans not only in terms of physiological aspects. In severe cases of the disease, even fainting, uncontrollable and unreasonable fear and hallucinations are possible.
The cardiovascular system suffers no less strongly from radiation. A particularly striking effect is seen in the category of neurocirculatory dystonia disorder:
- shortness of breath even without significant physical activity;
- pain in the heart area;
- a shift in the heartbeat rhythm, including “fading” of the heart muscle.
If during this period a person consults a cardiologist, the doctor may detect hypotension and muffled heart muscle tones in the patient. IN in rare cases The patient even has a systolic murmur at the apex.
The picture looks a little different if a person is exposed to microwaves on an irregular basis. In this case, he will have:
- slight malaise,
- feeling tired for no reason;
- pain in the heart area.
During physical activity, the patient will experience shortness of breath.
Schematically, all types of chronic exposure to microwaves can be divided into three stages, which differ in the degree of symptomatic severity.
The first stage provides for the absence characteristic features asthenia and neurocirculatory dystonia. Only isolated symptomatic complaints can be traced. If you stop irradiation, then after a while everything discomfort disappear without additional treatment.
At the second stage, more distinct signs are visible. But at this stage the processes are still reversible. This means that with proper and timely treatment, the patient will be able to regain his health.
The third phase is very rare, but still occurs. In this situation, a person experiences hallucinations, fainting, and even disturbances associated with sensitivity. An additional symptom may be coronary insufficiency.
Biological effect of microwave fields
Since each organism has its own unique characteristics, the biological effect of radiation may also vary from case to case. Several fundamental principles underlie the identification of the severity of a lesion: 
- radiation intensity,
- period of influence,
- wavelength,
- the original state of the body.
The last point includes chronic or genetic diseases of the individual victim.
The main danger from radiation is the thermal effect. It involves an increase in body temperature. But doctors also detect non-thermal effects in such cases. In such a situation, a classic increase in temperature does not occur. But physiological changes are still observed.
Thermal effect under a prism clinical analysis implies not only rapid growth temperatures, and:
- increased heart rate,
- shortness of breath,
- high blood pressure,
- increased salivation.
If a person was exposed to low-intensity rays for only 15-20 minutes, which did not exceed the maximum permissible standards, then various changes in the nervous system occur at the functional level. They all have varying degrees expressions. If several identical repeated irradiations are performed, the effect accumulates.
How to protect yourself from microwave radiation?
Before looking for methods of protection from microwave radiation, you first need to understand the nature of the influence of such an electromagnetic field. There are several factors to consider here:
- distance from the supposed source of the threat;
- exposure time and intensity;
- impulsive or continuous type of irradiation;
- some external conditions.
To calculate a quantitative assessment of the danger, experts introduced the concept of radiation density. In many countries, experts accept 10 microwatts per centimeter as the standard for this issue. In practice, this means that the power of the flow of dangerous energy in the place where a person spends most time, should not exceed this permissible limit.
Every person who cares about their health can independently protect themselves from possible danger. To do this, simply reduce the amount of time you spend around artificial sources Microwave rays.
A different approach to solving this problem is necessary for those people whose work is closely related to exposure to microwaves of various manifestations. They will need to use special means protection, which are divided into two types:
- individual,
- are common.
To minimize possible Negative consequences from the influence of such radiation, it is important to increase the distance from the worker to the source of exposure. Other effective measures to block the possible negative influence of rays are usually called:
- changing the direction of the rays;
- reduction of radiation flux;
- reducing the time period of exposure;
- use of a screening tool;
- remote control dangerous objects and mechanisms.
All existing protective screens aimed at preserving user health are divided into two subtypes. Their classification involves division according to the properties of the microwave radiation itself:
- reflective
- absorbing.
The first version of protective equipment is created on the basis of a metal mesh, or sheet metal and metallized fabric. Since the range of such assistants is quite large, employees of various hazardous industries there will be plenty to choose from.
The most common versions are sheet screens made of homogeneous metal. But for some situations this is not enough. In this case, it is necessary to enlist the support of multi-layer packages. Inside they will have layers of insulating or absorbent material. It can be ordinary shungite or carbon compounds.
The enterprise security service usually always pays special attention to personal protective equipment. They provide special clothing, which is created on the basis of metallized fabric. It can be:
- robes,
- aprons,
- gloves,
- capes with hoods.
When working with a radiation object or in dangerous proximity to it, you will additionally need to use special glasses. Their main secret is coating with a layer of metal. With this precaution it will be possible to reflect the rays. IN total wearing individual funds protection can reduce radiation exposure up to a thousand times. It is recommended to wear glasses at radiation levels of 1 µW/cm.
Benefits of microwave radiation
In addition to the popular belief about how harmful microwaves are, there is also the opposite statement. In some cases, microwaves can even bring benefits to humanity. But these cases must be carefully studied, and the radiation itself must be carried out in doses under the supervision of experienced specialists.
The therapeutic benefits of microwave radiation are based on its biological effects that occur during physical therapy. To generate rays in medicinal purposes(which is called stimulation) special medical generators are used. When they are activated, radiation begins to be produced in a clearly given by the system parameters.
Here, the depth specified by the expert is taken into account so that the heating of the tissues gives the promised positive effect. The main advantage of this procedure is the ability to provide high-quality analgesic and antipruritic therapy.
Medical generators are used around the world to help people who suffer from:
- frontitis,
- sinusitis,
- trigeminal neuralgia.
If the equipment uses microwave radiation with increased penetrating power, then with its help doctors successfully cure a number of diseases in the following areas:
- endocrine,
- respiratory,
- gynecological,
- kidneys
If you follow all the rules prescribed by the safety commission, then the microwave will not cause significant harm to the body. Direct to that proof is its use for medicinal purposes.
But if you violate operating rules by refusing to voluntarily limit yourself from strong sources of radiation, this can lead to irreparable consequences. Because of this, it is always worth remembering how dangerous microwaves can be when used unsupervised.
Among the huge variety of electromagnetic waves existing in nature, microwave or microwave radiation (microwave) occupies a very modest place. This frequency range can be found between radio waves and the infrared part of the spectrum. Its length is not particularly great. These are waves with a length of 30 cm to 1 mm.
Let's talk about its origin, properties and role in the human environment, about how this “silent invisibility” affects the human body.
Microwave radiation sources
Exist natural springs microwave radiation - Sun and others space objects. It was against the background of their radiation that the formation and development of human civilization took place.
But in our century, saturated with all kinds of technical achievements, man-made sources have also been added to the natural background:
- radar and radio navigation installations;
- satellite television systems;
- cell phones and microwave ovens.
How microwave radiation affects human health
The results of a study of the influence of microwave radiation on humans made it possible to establish that microwave rays do not have an ionizing effect. Ionized molecules are defective particles of matter that lead to mutation of chromosomes. As a result, living cells can acquire new (defective) characteristics. This finding does not mean that microwave radiation is not harmful to humans.
The study of the influence of microwave rays on humans has made it possible to establish the following picture - when they hit the irradiated surface, partial absorption of the incoming energy by human tissue occurs. As a result, high-frequency currents are excited in them, heating the body.
As a reaction of the thermoregulation mechanism, increased blood circulation follows. If the irradiation was local, rapid heat removal from heated areas is possible. At general exposure there is no such possibility, so it is more dangerous.
Since blood circulation acts as a cooling factor, the thermal effect is most pronounced in organs depleted of blood vessels. First of all, in the lens of the eye, causing its clouding and destruction. Unfortunately, these changes are irreversible.
The most significant absorption capacity is found in tissues with a high content of liquid components: blood, lymph, mucous membrane of the stomach, intestines, and the lens of the eye.
As a result, you may experience:
- changes in the blood and thyroid gland;
- decreased efficiency of adaptation and metabolic processes;
- changes in mental sphere, which can lead to depressive states, and in people with an unstable psyche - provoke suicidal tendencies.
Microwave radiation has a cumulative effect. If at first its effects are asymptomatic, then pathological conditions gradually begin to form. Initially, they manifest themselves in increased headaches, fatigue, sleep disturbances, increased blood pressure, and heart pain.
With prolonged and regular exposure to microwave radiation, it leads to the profound changes listed earlier. That is, it can be argued that microwave radiation has Negative influence on human health. Moreover, age-related sensitivity to microwaves was noted - young organisms turned out to be more susceptible to the influence of microwave EMF (electromagnetic field).
Means of protection against microwave radiation
The nature of the impact of microwave radiation on a person depends on the following factors:
- distance from the radiation source and its intensity;
- duration of irradiation;
- wavelength;
- type of radiation (continuous or pulsed);
- external conditions;
- state of the body.
For quantification danger, the concept of radiation density and permissible exposure rate was introduced. In our country, this standard is taken with a tenfold “safety margin” and is equal to 10 microwatts per centimeter (10 μW/cm). This means that the power of the microwave energy flow at a human workplace should not exceed 10 μW for each centimeter of surface.
How to be? The obvious conclusion is that exposure to microwave rays should be avoided in every possible way. Reducing exposure to microwave radiation in the home is quite simple: you should limit the time of contact with household sources.
People whose professional activity associated with exposure to microwave radio waves. Means of protection against microwave radiation are divided into general and individual.
The flux of emitted energy decreases in inverse proportion to the increase in the square of the distance between the emitter and the irradiated surface. Therefore, the most important collective protective measure is to increase the distance to the radiation source.
Other effective measures to protect against microwave radiation are the following:
Most of them are based on the basic properties of microwave radiation - reflection and absorption by the substance of the irradiated surface. Therefore, protective screens are divided into reflective and absorbent.
Reflective screens are made of sheet metal, metal mesh and metallized fabric. The arsenal of protective screens is quite diverse. These are sheet screens made of homogeneous metal and multilayer packages, including layers of insulating and absorbing materials (shungite, carbon compounds), etc.
The final link in this chain is personal protective equipment against microwave radiation. They include workwear made of metallized fabric (robes and aprons, gloves, capes with hoods and goggles built into them). The glasses are covered with a thin layer of metal that reflects radiation. They are required to be worn when exposed to radiation of 1 µW/cm.
Wearing protective clothing reduces the level of radiation exposure by 100–1000 times.
Benefits of microwave radiation
All previous information with a negative orientation is intended to warn our reader from the danger emanating from microwave radiation. However, among the specific actions of microwave rays there is the term stimulation, that is, improvement under their influence general condition the body or the sensitivity of its organs. That is, the effect of microwave radiation on humans can be beneficial. The therapeutic property of microwave radiation is based on its biological action during physiotherapy.
Radiation emanating from a specialized medical generator penetrates the human body to a given depth, causing tissue heating and a whole system of useful reactions. Sessions of microwave procedures have an analgesic and antipruritic effect.
They are successfully used to treat frontal sinusitis and sinusitis, trigeminal neuralgia.
To influence the endocrine organs, respiratory organs, kidneys, and treat gynecological diseases, microwave radiation with greater penetrating power is used.
Research into the effect of microwave radiation on the human body began several decades ago. The accumulated knowledge is enough to be confident in the harmlessness natural background of these radiations for humans.
Various generators of these frequencies create an additional dose of impact. However, their share is very small, and the protection used is quite reliable. Therefore, phobias about their enormous harm are nothing more than a myth if all operating conditions and protection from industrial and household sources microwave emitters.
Section "Engineering and technology for processing hydrobionts and agricultural raw materials"
IMPACT OF ELECTROMAGNETIC MICROWAVE FIELD ON THE HUMAN BODY Kraev A.A. (Department of Physics, MSTU) It is almost impossible to calculate in advance the amount of radiant energy absorbed by the human body in a given section of the electromagnetic field and converted into heat. The magnitude of this energy strongly depends on the basic electrical characteristics, position, size and structure of muscle and fat tissue and the direction of incidence of the wave, i.e. in other words, this value depends on the input resistance of a given complex structure. The direction of polarization of the incident wave relative to the body axis also plays a significant role. In each individual case, to establish symptoms it is necessary precise research existing conditions. The actual increase in body temperature depends on such parameters environment, like temperature and humidity, and from the body's cooling mechanism. Irradiation in an intense microwave field of living tissues leads to changes in their properties, which are associated with the thermal consequences of radiation absorption. To study these changes, living tissues can be divided into two classes: b) tissues that do not contain blood vessels. With appropriate regulation of the output power of the microwave generator and the duration of irradiation various fabrics, containing blood vessels, can be heated to almost any temperature. The temperature of the tissue begins to rise immediately after microwave energy is supplied to it. This temperature rise continues for 15-20 minutes and can increase the temperature of the tissue by 1-2 °C compared to average temperature body, after which the temperature begins to drop. The temperature drop in the irradiated area occurs as a result of a sharp increase in blood flow in it, which leads to a corresponding heat removal. The lack of blood vessels in some parts of the body makes them especially vulnerable to radiation ultra high frequencies. In this case, heat can only be absorbed by the surrounding vascular tissues, to which it can only flow through thermal conduction. This is particularly true for eye tissue and internal organs such as the gallbladder, bladder and gastrointestinal tract. The small number of blood vessels in these tissues complicates the process of auto-regulation of temperature. In addition, reflections from the boundary surfaces of body cavities and areas where the bone marrow is located under certain conditions leads to the formation standing waves. Excessive temperature increases in certain areas of standing waves can cause tissue damage. Reflections of this kind are also caused by metal objects located inside or on the surface of the body. When these tissues are intensively irradiated with a microwave field, they overheat, leading to irreversible changes. At the same time, low-power microwave fields have a beneficial effect on the human body, which is used in medical practice. Head and spinal cord sensitive to changes in pressure, and therefore the increase in temperature resulting from irradiation of the head can have serious consequences. The bones of the skull cause strong reflections, making it very difficult to estimate the absorbed energy. The increase in brain temperature occurs most rapidly when the head is irradiated from above or when the chest is irradiated, since heated blood from the chest is directly sent to the brain. Irradiation of the head causes a state of drowsiness followed by a transition to an unconscious state. With prolonged exposure, convulsions appear, which then turn into paralysis. When the head is irradiated, death inevitably occurs if the brain temperature rises by 6 °C. The eye is one of the organs most sensitive to irradiation by microwave energy, because it has a weak thermoregulatory system and the generated heat cannot be removed quickly enough. After 10 minutes of irradiation with a power of 100 W at a frequency of 2450 MHz, the development of cataracts (clouding of the eye lens) is possible, as a result of which the lens protein coagulates and forms visible white inclusions. At this frequency, the highest temperature occurs near the back surface of the lens, which consists of a protein that is easily damaged by heat. Male genital organs in highest degree sensitive to thermal effects and therefore particularly vulnerable to irradiation. Safe radiation density expressed as maximum level 5 mW/cm2 is significantly lower than for other radiation-sensitive organs. As a result of irradiation of the testes, temporary or permanent infertility may occur. Damage to genital tissue is especially considered, since some geneticists believe that small doses of radiation do not lead to any physiological disorders, but at the same time can cause gene mutations that remain hidden for several generations.
The range of radio emission is the opposite of gamma radiation and is also unlimited on one side - from long waves and low frequencies.
Engineers divide it into many sections. The shortest radio waves are used for wireless data transmission (Internet, cellular and satellite telephony); meter, decimeter and ultrashort waves (VHF) occupy local television and radio stations; short waves (HF) are used for global radio communications - they are reflected from the ionosphere and can circle the Earth; medium and long waves are used for regional radio broadcasting. Ultra-long waves (ELW) - from 1 km to thousands of kilometers - penetrate through salt water and are used to communicate with submarines, as well as for searching for minerals.
The energy of radio waves is extremely low, but they excite weak vibrations of electrons in a metal antenna. These vibrations are then amplified and recorded.
The atmosphere transmits radio waves with a length from 1 mm to 30 m. They make it possible to observe the nuclei of galaxies, neutron stars, other planetary systems, but the most impressive achievement of radio astronomy is record-breaking detailed images of cosmic sources, the resolution of which exceeds ten-thousandths of an arcsecond.
Microwave
Microwaves are a subband of radio emission adjacent to the infrared. It is also called ultra-high frequency (microwave) radiation because it has the highest frequency in the radio range.
The microwave range is of interest to astronomers because it records what remains from time big bang cosmic microwave background radiation (another name is the microwave cosmic background). It was emitted 13.7 billion years ago, when the hot matter of the Universe became transparent to its own thermal radiation. As the Universe expanded, the CMB cooled and today its temperature is 2.7 K.
CMB radiation comes to Earth from all directions. Today, astrophysicists are interested in inhomogeneities in the sky glow in the microwave range. They are used to determine how galaxy clusters began to form in the early Universe in order to test the correctness of cosmological theories.
But on Earth, microwaves are used for such mundane tasks as heating breakfast and talking on a cell phone.
The atmosphere is transparent to microwaves. They can be used to communicate with satellites. There are also projects for transmitting energy over a distance using microwave beams.
Sources
Sky Reviews
Microwave sky 1.9 mm(WMAP)
The cosmic microwave background, also called the cosmic microwave background radiation, is the cooled glow of the hot Universe. It was first discovered by A. Penzias and R. Wilson in 1965 ( Nobel Prize 1978) The first measurements showed that the radiation is completely uniform throughout the sky.
In 1992, the discovery of anisotropy (inhomogeneity) of the cosmic microwave background radiation was announced. This result was obtained by the Soviet satellite Relikt-1 and confirmed American satellite COBE (see Infrared Sky). COBE also determined that the spectrum of the cosmic microwave background radiation is very close to that of the blackbody. The 2006 Nobel Prize was awarded for this result.
Variations in the brightness of the cosmic microwave background radiation across the sky do not exceed one hundredth of a percent, but their presence indicates subtle inhomogeneities in the distribution of matter that existed at an early stage of the evolution of the Universe and served as the embryos of galaxies and their clusters.
However, the accuracy of the COBE and Relikt data was not enough to verify cosmological models, and therefore in 2001 a new, more accurate WMAP (Wilkinson Microwave Anisotropy Probe) apparatus was launched, which by 2003 had built detailed map distribution of the intensity of the cosmic microwave background radiation according to celestial sphere. Based on these data, cosmological models and ideas about the evolution of galaxies are now being refined.
CMB arose when the age of the Universe was about 400 thousand years and, due to expansion and cooling, it became transparent to its own thermal radiation. Initially, the radiation had a Planck (blackbody) spectrum with a temperature of about 3000 K and accounted for the near-infrared and visible ranges of the spectrum.
As the Universe expanded, the cosmic microwave background radiation experienced a red shift, which led to a decrease in its temperature. Today the temperature of the cosmic microwave background radiation is 2.7 TO and it falls in the microwave and far-infrared (submillimeter) ranges of the spectrum. The graph shows an approximate view of the Planck spectrum for this temperature. The spectrum of the cosmic microwave background radiation was first measured by the COBE satellite (see Sky in the infrared), for which the Nobel Prize was awarded in 2006.
Radio sky on wave 21 cm, 1420 MHz(Dickey & Lockman)
Famous spectral line with wavelength 21.1 cm is another way to observe neutral atomic hydrogen in space. The line arises due to the so-called hyperfine splitting of the main energy level of the hydrogen atom.
The energy of an unexcited hydrogen atom depends on the relative orientation of the spins of the proton and electron. If they are parallel, the energy is slightly higher. Such atoms can spontaneously transform into a state with antiparallel spins, emitting a quantum of radio emission that carries away a tiny excess of energy. This happens to an individual atom on average once every 11 million years. But the huge distribution of hydrogen in the Universe makes it possible to observe gas clouds at this frequency.
Radio sky on wave 73.5 cm, 408 MHz(Bonn)
This is the longest wavelength of all sky surveys. It was performed at a wavelength at which a significant number of sources are observed in the Galaxy. In addition, the choice of wavelength was determined by technical reasons. To construct the survey, one of the world's largest full-rotating radio telescopes was used - the 100-meter Bonn radio telescope.
Terrestrial Application
Main advantage microwave oven- warming up the products over time throughout the entire volume, and not just from the surface.
Microwave radiation, having a longer wavelength, penetrates deeper than infrared radiation under the surface of products. Inside products electromagnetic vibrations excite rotational levels of water molecules, the movement of which mainly causes heating of food. In this way, microwave (microwave) drying of food, defrosting, cooking and heating takes place. Also variables electric currents excite high frequency currents. These currents can occur in substances where mobile charged particles are present.
But sharp and thin metal objects cannot be placed in a microwave oven (this especially applies to dishes with metal decorations coated with silver and gold). Even a thin ring of gilding along the edge of a plate can cause a powerful electrical discharge, which will damage the device creating electromagnetic wave in a furnace (magnetron, klystron).
The operating principle of cellular telephony is based on the use of a radio channel (in the microwave range) for communication between the subscriber and one of the base stations. Information is transmitted between base stations, as a rule, via digital cable networks.
The range of the base station - the size of the cell - is from several tens to several thousand meters. It depends on the landscape and on the signal strength, which is selected so that there are not too many active subscribers in one cell.
In the GSM standard, one base station can provide no more than 8 telephone conversations simultaneously. On mass events and at natural disasters the number of calling subscribers increases sharply, this overloads base stations and leads to interruptions in cellular communications. In such cases mobile operators There are mobile base stations that can be quickly delivered to areas with large crowds of people.
The question of possible harm microwave radiation from cell phones. During a conversation, the transmitter is in close proximity from a person's head. Repeated studies have not yet been able to reliably register negative impact radio emissions from cell phones on health. Although the effects of weak microwave radiation on body tissue cannot be completely ruled out, there is no cause for serious concern.
Television images are transmitted on meter and decimeter waves. Each frame is divided into lines along which the brightness changes in a certain way.
The transmitter of a television station constantly broadcasts a radio signal of a strictly fixed frequency, it is called the carrier frequency. The receiving circuit of the TV is adjusted to it - a resonance arises in it at the desired frequency, which makes it possible to pick up weak electromagnetic oscillations. Information about the image is transmitted by the amplitude of the oscillations: large amplitude means high brightness, low amplitude means a dark area of the image. This principle is called amplitude modulation. Sound is transmitted similarly by radio stations (except FM stations).
With the transition to digital television, the rules for image encoding change, but the very principle of the carrier frequency and its modulation remains the same.
Parabolic antenna for receiving a signal from a geostationary satellite in the microwave and VHF ranges. The principle of operation is the same as that of a radio telescope, but the dish does not need to be made movable. At the time of installation, it is directed to the satellite, which always remains in one place relative to earthly structures.
This is achieved by placing the satellite on geostationary orbit height of about 36 thousand. km above the Earth's equator. The period of revolution along this orbit is exactly equal to the period of rotation of the Earth around its axis relative to the stars - 23 hours 56 minutes 4 seconds. The size of the dish depends on the power of the satellite transmitter and its radiation pattern. Each satellite has a primary service area where its signals are received by a dish with a diameter of 50–100 cm, and the peripheral zone, where the signal quickly weakens and an antenna of up to 2–3 may be required to receive it. m.
I was very surprised when my simple homemade detector-indicator went off scale next to a working microwave oven in our work canteen. It’s all shielded, maybe there’s some kind of malfunction? I decided to check out my new stove; it had hardly been used. The indicator also deviated to the full scale!
I assemble such a simple indicator in a short time every time I go to field tests of transmitting and receiving equipment. It helps a lot in work, you don’t have to carry a lot of equipment with you, it’s always easy to check the functionality of the transmitter with a simple homemade product (where the antenna connector is not fully screwed in, or you forgot to turn on the power). Customers really like this style of retro indicator and have to leave it as a gift.
The advantage is the simplicity of the design and the lack of power. Eternal device.
It’s easy to do, much simpler than the exact same “Detector from a network extension cord and a bowl of jam” in the mid-wave range. Instead of a network extension cord (inductor) - a piece of copper wire; by analogy, you can have several wires in parallel, it won’t be any worse. The wire itself in the form of a circle 17 cm long, at least 0.5 mm thick (for greater flexibility I use three such wires) is like oscillatory circuit below, and with a loop antenna of the upper part of the range, which ranges from 900 to 2450 MHz (I did not check the performance above). It is possible to use a more complex directional antenna and input matching, but such a deviation would not correspond to the title of the topic. A variable, built-in or just a capacitor (aka a basin) is not needed, for a microwave there are two connections next to each other, already a capacitor.
There is no need to look for a germanium diode; it will be replaced by a PIN diode HSMP: 3880, 3802, 3810, 3812, etc., or HSHS 2812 (I used it). If you want to move above the frequency of the microwave oven (2450 MHz), choose diodes with a lower capacitance (0.2 pF), HSMP -3860 - 3864 diodes may be suitable. When installing, do not overheat. It is necessary to solder spot-quickly, in 1 second.
Instead of high-impedance headphones there is a dial indicator. The magnetoelectric system has the advantage of inertia. The filter capacitor (0.1 µF) helps the needle move smoothly. The higher the indicator resistance, the more sensitive the field meter (the resistance of my indicators ranges from 0.5 to 1.75 kOhm). The information contained in a deviating or twitching arrow has a magical effect on those present.
Such a field indicator, installed next to the head of a person talking on a mobile phone, will first cause amazement on the face, perhaps bring the person back to reality, and save him from possible diseases.
If you still have strength and health, be sure to point your mouse at one of these articles.
Instead of a pointer device, you can use a tester that will measure constant pressure at the most sensitive limit.
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| Microwave indicator circuit with LED. |
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| Microwave indicator with LED. |
Tried it LED as indicator. This design can be designed in the form of a keychain using a flat 3-volt battery, or inserted into an empty mobile phone case. The standby current of the device is 0.25 mA, the operating current directly depends on the brightness of the LED and will be about 5 mA. The voltage rectified by the diode is amplified by the operational amplifier, accumulated on the capacitor and opens the switching device on the transistor, which turns on the LED.
If the dial indicator without a battery deviated within a radius of 0.5 - 1 meter, then the color music on the diode moved up to 5 meters, as from cell phone, and from a microwave oven. I was not mistaken about color music, see for yourself that the maximum power will only be when talking on a mobile phone and in the presence of extraneous loud noise.
Adjustment.
I collected several such indicators, and they worked immediately. But there are still nuances. When turned on, the voltage on all pins of the microcircuit, except the fifth, should be equal to 0. If this condition is not met, connect the first pin of the microcircuit through a 39 kOhm resistor to minus (ground). It happens that the configuration of microwave diodes in the assembly does not coincide with the drawing, so you must adhere to electrical diagram, and before installation, I would advise you to ring the diodes for their compliance.
For ease of use, you can worsen the sensitivity by reducing the 1 mOhm resistor, or reducing the length of the wire turn. With the given field values, microwave base telephone stations can be sensed within a radius of 50 - 100 m.
With such an indicator you can make environmental map your area and allocate places where you cannot hang out with strollers or stay for a long time with children.
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Be under base station antennas |
Analog level indicator.
I decided to try to make the microwave indicator a little more complex, for which I added an analog level meter to it. For convenience, I used the same element base. The circuit shows three DC operational amplifiers with different gains. In the layout, I settled on 3 stages, although you can plan a 4th one using the LMV 824 microcircuit (4th op-amp in one package). Having used power from 3, (3.7 telephone battery) and 4.5 volts, I came to the conclusion that it is possible to do without a key stage on a transistor. Thus, we got one microcircuit, a microwave diode and 4 LEDs. Taking into account the conditions of strong electromagnetic fields in which the indicator will operate, I used blocking and filtering capacitors for all inputs, feedback circuits and op-amp power supply.
Adjustment.
When turned on, the voltage on all pins of the microcircuit, except the fifth, should be equal to 0. If this condition is not met, connect the first pin of the microcircuit through a 39 kOhm resistor to minus (ground). It happens that the configuration of microwave diodes in the assembly does not coincide with the drawing, so you need to adhere to the electrical diagram, and before installation I would advise you to ring the diodes to ensure their compliance.
This prototype has already been tested.
The interval from 3 illuminated LEDs to completely extinguished ones is about 20 dB.
Power supply from 3 to 4.5 volts. Standby current from 0.65 to 0.75 mA. The operating current when the 1st LED lights up is from 3 to 5 mA.
This microwave field indicator on a chip with a 4th op amp was assembled by Nikolai.
Here is his diagram.
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| Dimensions and pin markings of the LMV824 microcircuit. |
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| Installation of microwave indicator on the LMV824 chip. |
The MC 33174D microcircuit, which has similar parameters and includes four operational amplifiers, is housed in a dip package and is larger in size and therefore more convenient for amateur radio installation. The electrical configuration of the pins completely coincides with the L MV 824 microcircuit. Using the MC 33174D microcircuit, I made a layout of a microwave indicator with four LEDs. A 9.1 kOhm resistor and a 0.1 μF capacitor in parallel with it are added between pins 6 and 7 of the microcircuit. The seventh pin of the microcircuit is connected through a 680 Ohm resistor to the 4th LED. The standard size of the parts is 06 03. The breadboard is powered by a lithium cell of 3.3 - 4.2 volts.
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| Indicator on the MC33174 chip. |
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| Reverse side. |
The original design of the economical field indicator is a souvenir made in China. This inexpensive toy contains: a radio, a clock with a date, a thermometer and, finally, a field indicator. The unframed, flooded microcircuit consumes negligibly little energy, since it operates in a timing mode; it reacts to turning on a mobile phone from a distance of 1 meter, simulating a few seconds of LED indication of an emergency alarm with headlights. Such circuits are implemented on programmable microprocessors with a minimum number of parts.
Addition to comments.
Selective field meters for the amateur band 430 - 440 MHz
and for the PMR band (446 MHz).
Indicators of microwave fields for amateur bands from 430 to 446 MHz can be made selective by adding an additional circuit L to SK, where L to is a turn of wire with a diameter of 0.5 mm and a length of 3 cm, and SK is a trimming capacitor with a nominal value of 2 - 6 pF . The turn of wire itself, as an option, can be made in the form of a 3-turn coil, with a pitch wound on a mandrel with a diameter of 2 mm with the same wire. An antenna in the form of a piece of wire 17 cm long must be connected to the circuit through a 3.3 pF coupling capacitor.
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| Range 430 - 446 MHz. Instead of a turn, there is a step-wound coil. |
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| Diagram for ranges 430 - 446 MHz. |
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| Frequency range mounting 430 - 446 MHz. |
By the way, if you are serious about microwave measurements of individual frequencies, you can use selective SAW filters instead of a circuit. In the capital's radio stores their assortment is currently more than sufficient. You will need to add an RF transformer to the circuit after the filter.
But this is another topic that does not correspond to the title of the post.