Our favorite HF Antennas. Shortwave antennas on the amateur bands, is and remains one of the hot topics in amateur radio. The beginner looks at which antenna to use and the aces of the ether look from time to time to see what new has appeared.

You don't have to stand still, but improve your results constantly, so we are going along this path, understanding and improving our antennas. You can even single out some radio amateurs into a separate group - Antenchiki.

Recently antennas and ready-made ones have become more affordable. But, even having bought such an antenna along with the installation, the owner, in our case, the radio amateur should have an idea.

In my mind, everything starts from the place where our antennas will be placed, then the antennas themselves. Of course, the choice of location is not given to everyone, but here we can win great, and how to choose, not everyone has such a flair, but there are such radio amateurs.

HF Antennas come first

Technically, it is difficult to compare the place on HF (on VHF it is simple and the measurements show a difference of four decibels). Let those who have such a choice of location be lucky. For the high-frequency ranges, the choice of antennas is larger and the dimensions are tolerable, but for the low-frequency ranges, the choice of finished antennas is smaller. And it's understandable - not everyone can afford five yagi elements for a range of 80 meters. Here the field of work can be large if the radio amateur has such a field for placing antennas on the low frequency bands

There is such a book where there is a lot of information on antennas for the low frequency ranges.

HF and VHF amateur antennas

An antenna is a device participating in the process of transmitting electromagnetic energy from a power line to free space, and vice versa. Each antenna has an active element, such as a vibrator, and may also contain one or more passive elements. The active element of the antenna is a vibrator, as a rule. directly connected to the power line. The emergence alternating voltage on the vibrator is associated both with the propagation of a wave in the power line, and with the appearance of an electromagnetic field around the vibrator.

Ideal antenna for HAM communications per kv

What kind of antennas do we radio amateurs use? What do we need? Do we need an ideal antenna for meter bands. Say that there are no such people, and that nothing is perfect at all. Then close to perfect. What for? You ask. Anyone who wants to achieve results, to go forward, sooner or later will come to this issue. Let's take a look at how to understand the ideal antenna on the meter amateur bands.

Why exactly on amateur meters, but because our correspondents are at different distances in different directions of the world. Let's add here the local conditions, where the antenna is located, and the conditions for the passage of radio waves at a given time on these frequencies. There will be many unknowns. What is the angle of radiation, what polarization will be maximum in a specific period of time with a specific correspondent (territory).

Yes, someone might get lucky. With a place, choice of antennas, suspension height. So what should you do? To be always lucky. We need an antenna that at any time will have the best parameters for a given transmission of radio waves from any territory. More = We scan (rotate) the antenna in azimuth, this is good. This is the first condition. The second condition = we need to scan along the angle of radiation in the vertical plane.

If someone does not know, depending on the conditions of passage, the signal can come from different angles from the same correspondent. The third condition is polarization. Scanning or changing polarization from horizontal to vertical polarization and back, smoothly or stepwise. Having created and received these three conditions in one antenna, we get ideal antenna for radio amateur communication on short waves.

Ideal antenna

Ideal antenna so what it is. If we consider, for example, satellite dishes, then perhaps it becomes clearer, easier to understand. Here we take the size (diameter of the cymbal), this is a direct dependence on the gain. One satellite - for example, we took a 60cm antenna. diameter. The signal level at the receiver input will be small, and sometimes we will not see the picture. Let's take an antenna with a diameter of 130 cm. The level is normal, the picture is stable.

Now let's take an antenna with a diameter of 4 meters and what we can observe. Sometimes the picture disappears. Yes, there can be two reasons. This wind swung our 4-meter antenna and the signal disappeared. This satellite in orbit does not keep its coordinates stably. So it turns out, on the one hand, a 4-meter antenna is the best in terms of gain, on the other hand, it is not optimal, which means it is not ideal. In this case, the optimal antenna is 130 cm. In this case, why can't we call it ideal?

So it is on the meter radio amateur bands. Not always five yagi elements at 40 meters will be optimal for the 80 meter range. So they are not perfect. You can even give a few examples from practice. In his laboratory work, he made 3 elements for a 10-meter range. Passive elements are curved inwardly active. Then a three-band version of such an antenna will come into fashion under the well-known name.

I listened, twisted and, of course, made connections to this antenna, the first impression is wonderful. Then the weekend came, another contest. But when I switched on to 10-ku with this antenna, then silence, I think, yesterday the range thundered, but today there is no passage.

From time to time I switched on this range in order to listen, suddenly a passage would begin. At the next call to 10-ku, numerous radio amateur stations stunned me - it began. And then I immediately discover that the wrong antenna is connected. Instead of 3-elements, it turned out to be a pyramid for the 80-meter range. I switch to 3 elements - silence, signals are thundering to the pyramid. I went outside, examined 3 elements, maybe what happened, no, everything is fine.

Then I worked well at 28 megahertz, made a lot of connections to the pyramid for the 80-meter range. On Monday, Tuesday the same picture was observed, and only on Wednesday it seemed to fall into place. Silence on the pyramid, but thundering on 3-elements. What is the difference? The difference in the angle of radiation.

In my pyramid there is radiation at 28 MHz. at an angle of 90 degrees, that is, to the zenith, and at a 3-element angle below 20 degrees. This practical example gives us something to think about. Another example, when I was in the zero area. I hear a call for the zero region on the 20-ke, I know that this friend has an antenna for several thousand dollars, that it is at a good height and the power amplifier is no less than a kilowatt. I call him, but he does not hear, or rather, he hears, but he cannot make out the call sign.

He twirled his expensive antenna, there was no sense, and out loud he said like that there is no passage today. Here at this frequency I hear - and you accept me. Yes, I accept. It turned out to be his neighbor and with only five watts and the antenna is such that I have already forgotten (perhaps, like a triangle for 80). We made a radio contact, and he was pleasantly surprised to know what kind of antenna and power the neighbor has. I don’t know how many meters or kilometers there are between them, but in that case the steep antenna was powerless.

Low frequency antennas

There was such laboratory work on both 40 and 80 meter bands. All this is in search of which antenna is better. And there is a moment where radio amateurs have the opportunity to work on such an antenna so that it is optimal at any time, and therefore ideal. Partly radio amateurs use some points that should be incorporated into an ideal antenna.

The simplest is the azimuth adjustment. The second in terms of radiation angle - we put the same antennas on different masts, at different heights or on one while commuting them into stacks. We get different angles of radiation. And also different antennas with different polarization, some have. But this is partly, not as a whole.

And some will say, why such an antenna. Ten kilowatts and the first place in your pocket. Yes, it's your choice. In this case, you are deceiving not only everyone, but first of all yourself. Or who has been using such an antenna on HF for a long time (there is on VHF), where the properties of an ideal antenna are laid down.

Our antennas

What is your antenna? 84 meters 27 centimeters and 28 meters of cable. Wow, but I have 32 centimeters, I need to shorten it, try like yours. This is our talk about antennas on the air. Here is a slightly different answer: I have a cable of three meters, I sit near the window itself, and outside the window there is an antenna right away. Three is bad, you do 28, you know how great the antenna will work. But literally yesterday I heard, and the conversation was between two experienced radio amateurs. And the conversation was about some secret antenna, about secret dimensions.

kv antenna

For many radio amateurs, this topic has been, is and will be one of the most demanded. Which antenna to choose, which one to buy. In either case, we need to mount it, install it, configure it, here we need some knowledge on antenna topics, here will help magazines books on antenna topics. So that, in the end, we understand something.

The radio amateur's antenna should be one of the first lines. Ksv is not an indicator and it is not necessary to chase after it in the first place. That an antenna with a SWR = 2 can work much better than an antenna with SWR = 1. And the efficiency drops with increasing elements and much more.

kv antenna

Log-periodic wire antenna for 40 meters. Everything is simple and effective. Several variants of sloper antennas for low frequency ranges 40,80,160 meters. Scanned antenna RA6AA, setup, used parts. In the magazine Radio amateur 1 1991. Read in full.

Practice of tuning and mounting antennas. Raising the mast. Options for attaching antenna canvases to a tree. Adjustment using the GSS and a lamp voltmeter in the magazine Radio Amateur 2 1991. Read.

In the seventh issue of 91 years of the magazine, Radio Amateur RA6AEG talks about his M antenna.

All this information is primarily for those who already have the callsign of an amateur radio station, as well as for everyone else who has not yet come to HF.

Capital structures and balcony railing can be successfully used to fix the antenna in cases where the installation of this device on the roof of a building for some reason is not possible. Of course, a HF balcony antenna does not compare in efficiency with the basic one, but for many tasks its capabilities will be quite acceptable. In this article, we will consider in detail a number of issues related to the operation of this kind of antennas, and we will learn how to make them ourselves.

catch the wave

Today, balcony antennas can often be seen on the facades of urban high-rise buildings. Almost all of them are designed for shortwave operation. With the help of such antennas, you can receive radio and television broadcasting signals, they also allow you to use radio stations for amateur or commercial (professional) radio communication. It should be noted that such devices are better at receiving radio signals than transmitting.

A self-made balcony HF antenna can always be fixed on the elements of the metal crate, since it has a low weight and small overall dimensions. Just first you should make sure that the device receives the signal you need clearly enough. The fact is that due to the shielding properties of the building, the balcony antenna works effectively only in some directions, and if your balcony or loggia "looks" in the direction opposite to the signal source, it may be absolutely useless.

What radio waves are called short? This category includes electromagnetic radiation with a wavelength of 10 to 100 m... The frequency range of 3 - 30 MHz corresponds to these lengths. A remarkable property of these radio waves is their ability to reflect from the surface of the earth and the upper layers of the atmosphere, practically without losing power. Thanks to this, the wave, as it were, flows around the surface of the planet, which makes it possible to transmit signals over long distances.

If you notice a deterioration in the quality of communication, do not rush to take the antenna for scrap. Short wave radio communications are very sensitive to many factors, among which the main ones are the time of day, weather conditions and the nature of solar activity. These factors affect the reception and transmission of a signal with a balcony antenna, which is inferior in its capabilities to the base antenna. Another reason for signal level changes is interference. Waves from the same source reach the antenna along different paths, which have, respectively, different durations. This is the reason for this phenomenon.

We design an antenna for the HF band

Those who have a hand in the morning instead of a toothbrush reach for a soldering iron will probably be interested in how to make a homemade antenna from scrap materials. Primarily, we need a ferrite tube- shielding element for cables from monitors and keyboards. Some radio amateurs accidentally discovered that such tubes react with a reactive impedance within a few hundred ohms to radio signals with a wavelength of slightly less than 100 m. At the same time, a broadband transformer on such tubes demonstrates good frequency characteristics within the shortwave range. These properties of ferrite tubes will help us design an HV antenna for a balcony or loggia. To do this, you must follow the step-by-step instructions:

Once installed on the balcony, such a homemade HF antenna demonstrates good reception of signals with a frequency of 14 to 28 MHz.

Read about in our article. It also features other models such as floor and ceiling.

If you are wondering:, then you will find the answer to it on our website.

Setting up an amateur connection

In the territory Russian Federation two radio frequency bands are open:

— range CB(Latin letters, the marking is read as "si-bi"), which is shortwave;

— PMR or LPD range, which is ultrashort wave.

They are called open because they can be used without special permission. However, there is one caveat: commercial use of the PMR band is not allowed.

CB waves (27 MHz) are able to bend around buildings, natural hills and woodlands. They are characterized by insignificant losses, so the antenna can be connected to the radio station using even cheap cable brands. The installation of base antennas for operation in the CB-band does not contradict the legislation.

For CB frequencies, the long-range effect is characteristic, which is caused by changes in solar activity or in the state of the magnetic field of our planet. It consists in the fact that a signal from a source distant 10-15 thousand km is received more clearly than from a station operating several kilometers away.

VHF signals (PMR and LPD) are transmitted at frequencies from 433 to 446 MHz. A mobile radio station operating on the LPD band is perfect for organizing communication, for example, between an office and a warehouse. Unlike equipment "sharpened" for the CB-band, such stations support multi-channel communication and are equipped with very efficient built-in antennas. In addition, LPD stations can be used to organize communication within a building, and their signals can even reach the basement.

Tip: To listen to and communicate with other radio amateurs' radios the best way a radio station with AM / FM and a base antenna CB will do. Such equipment will enable you to listen to both local stations and foreign radio broadcasting.

In one of his books in the late 1980s, W6SAI, Bill Orr proposed a simple antenna - 1 element square, which was mounted vertically on a single mast. The W6SAI antenna was made with the addition of an RF choke. The square is made for a range of 20 meters (Fig. 1) and is installed vertically on one mast. In continuation of the last knee of a 10-meter army telescope, fifty centimeters of fiberglass is inserted, in the shape of nothing different from the upper knee of the telescope, with a hole at the top, which is the upper insulator. The result is a square with an angle at the top, an angle at the bottom and two corners on the braces on the sides.In terms of efficiency, this is the most profitable option for placing the antenna, which is located low above the ground. The feeding point was about 2 meters from the underlying surface. The cable connection unit is a piece of thick fiberglass 100x100 mm, which is attached to the mast and serves as an insulator. The perimeter of the square is equal to 1 wavelength and is calculated by the formula: Lm = 306.3 \ F MHz. For a frequency of 14.178 MHz. (Lm = 306.3 \ 14.178) the perimeter will be 21.6 m, i.e. side of the square = 5.4 m. Power supply from the bottom corner with a 75 ohm cable 3.49 meters long, i.e. 0.25 wavelength. This piece of cable is a quarter-wave transformer, transforming Rin. antennas of the order of 120 ohms, depending on the objects surrounding the antenna, with a resistance close to 50 ohms. (46.87 ohms). Most of the 75 ohm length of cable runs vertically along the mast. Further, through the RF connector, the main transmission line is a 50 Ohm cable with a length equal to an integer number of half-waves. In my case, this is a section of 27.93 m, which is a half-wave repeater. This method of powering is well suited for 50 ohm technology, which today corresponds to R out in most cases. ShPU transceivers and the nominal output impedance of power amplifiers (transceivers) with a P-circuit at the output. When calculating the cable length, remember about the shortening factor of 0.66-0.68, depending on the type of plastic cable insulation. With the same 50 ohm cable, an RF choke is wound next to the mentioned RF connector. Its data: 8-10 turns on a 150mm mandrel. Winding coil to coil. For antennas for low frequency ranges - 10 turns on a mandrel 250 mm. The RF choke eliminates the curvature of the antenna radiation pattern and acts as a Shut-off Choke for HF currents moving along the cable sheath towards the transmitter. The antenna bandwidth is of the order of 350-400 kHz. with VSWR close to unity. Outside the bandwidth, the VSWR rises dramatically. Antenna polarization is horizontal. The braces are made of wire with a diameter of 1.8 mm. broken by insulators at least every 1-2 meters. If you change the feed point of the square by feeding it from the side, as a result we get vertical polarization, more preferable for DX. Use the same cable as for horizontal polarization, i.e. a quarter-wave piece of 75 Ohm cable goes to the frame (the central core of the cable is connected to the upper half of the square, and the braid to the bottom), and then the 50 Ohm cable is a multiple of half-wave. The resonant frequency of the frame will go up by about 200 kHz when the power point is changed. (at 14.4 MHz.), so the frame will have to be lengthened somewhat. An extension wire, a cable of about 0.6-0.8 meters, can be connected to the lower corner of the frame (to the former power point of the antenna). To do this, you need to use a section of a two-wire line of the order of 30-40 cm. Wave resistance does not play a big role here. A jumper is soldered on the loop at a minimum VSWR. The angle of radiation will be 18 degrees, not 42, as with horizontal polarization. It is highly desirable to ground the mast at the base.

Antenna horizontal frame

The HF band contains a number of radio frequencies (27 MHz, commonly used by drivers), broadcasting by many stations. There are no TV programs here. Today we will take a look at the amateur series employed by various radio communication enthusiasts. Frequencies 3.7; 7; fourteen; 21, 28 MHz of the HF range, related as 1: 2: 4: 6: 8. It is important, as we will see later, it becomes possible to make an antenna that would catch all the ratings (the question of matching is the tenth thing). We believe there will always be people using the information, catch radio broadcasts. Today's topic is a do-it-yourself HF antenna.

We will disappoint many, today we will again talk about vibrators. The objects of the Universe are formed by vibrations (the views of Nikola Tesla). Life attracts life, it is movement. To give life to a wave, vibrations are necessary. Changes in the electric field generate a magnetic response, thus crystallizing the frequency that carries information to the ether. The immobilized field is dead. A permanent magnet will not generate a wave. Figuratively speaking, electricity is a masculine principle, it exists only in motion. Magnetism is more of a feminine quality. However, the authors delved into philosophy.

It is believed that horizontal polarization is preferred for transmission. Firstly, the azimuth pattern is not circular (they casually said), there will certainly be less interference. We know that various objects are equipped for communication, such as ships, cars, tanks. You can't lose commands, orders, words. The object will turn in the wrong direction, and the polarization is horizontal? Disagree with well-known, respected authors who write: vertical polarization is chosen by the connection for an antenna of a simpler design. Talk about the case of amateurs, it's more about the continuity of the heritage of previous generations.

Let us add: with horizontal polarization, the parameters of the Earth have less influence on wave propagation, in addition, with a vertical front, the front suffers attenuation, the lobe rises to 5 - 15 degrees, it is undesirable when transmitting over long distances. For antennas (unbalanced) with vertical polarization, good grounding is important. The efficiency of the antenna directly depends. It is better to bury the wires with a length of about a quarter of a wave with earth, the more, the higher the efficiency. Example:

• 2 wires - 12%;
• 15 wires - 46%;
• 60 wires - 64%;
• ∞ wires - 100%.

An increase in the number of wires reduces the characteristic impedance, approaching the ideal (of the indicated type of vibrator) - 37 ohms. Note, the quality should not be brought closer to the ideal, 50 Ohm does not need to be coordinated with the cable (in connection, RK - 50 is used). Great thing. Let's supplement the information package with a simple fact, with horizontal polarization, the signal is added to the reflected Earth, giving an increase of 6 dB. So many minuses are shown by vertical polarization, they are used (it turned out interestingly with ground wires), they put up with it.

The device of HF antennas is reduced to a simple quarter-wave, half-wave vibrator. The latter are smaller in size, accept worse, the latter are easier to agree on. The masts are placed vertically, using spacers, stretch marks. Described a structure hung on a tree. Not everyone knows: there should be no interference at half a wavelength from the antenna. Applies to iron, reinforced concrete structures. Wait a moment to rejoice, at a frequency of 3.7 MHz the distance is ... 40 meters. The antenna reaches the eighth floor in height. Making a quarter-wave vibrator is not easy.

It is convenient to erect a tower to listen to the radio, we decided to recall the old way of catching long waves. Internal ferromagnetic antennas are found in Soviet-era receivers. Let's see if the designs are suitable for their intended purpose (catching broadcasting).

HF magnetic antenna

Let's say there is a need to accept frequencies from 3.7 to 7 MHz. Let's see if it is possible to design a magnetic antenna. Formed by a core of round, square, rectangular cross-section. The sizes are recalculated by the formula:

do = 2 √ pc / π;

do is the diameter of the round bar; h, c - height, width of the rectangular section.

Winding is not carried out the entire length, in fact, you need to calculate how much to wind, choose the type of wire. Let's take an example of an old design textbook, let's try to calculate a HF antenna of frequencies from 3.7 to 7 MHz. Let us take the resistance of the input stage of the receiver 1000 Ohm (in practice, readers measure the input resistance of the receiver on their own), the parameter of the equivalent attenuation of the input circuit, at which the specified selectivity is achieved, der equal to 0.04.

The antenna we are designing is part of the resonant circuit. It turns out a cascade, endowed with a certain selectivity. How to solder, think for yourself, just follow the formulas. Carrying out the calculation will need to find the maximum, minimum capacity of the trimmer capacitor, using the formula: Cmax = K 2 Cmin + Co (K 2 - 1).

K is the coefficient of the sub-band, determined by the ratio of the maximum resonant frequency to the minimum. In our case, 7 / 3.7 = 1.9. Chosen from incomprehensible (according to the textbook) considerations, for example, given in the text, take equal to 30 pF. Let's not make a big mistake. Let Cmin = 10 pF, we find the upper limit of the adjustment:

Cmax = 3.58 x 10 + 30 (3.58 - 1) = 35.8 + 77.4 = 110 pF.

Rounded, of course, you can take a variable capacitor of a larger range. An example gives 10-365 pF. We calculate the required inductance of the circuit using the formula:

L = 2.53 x 10 4 (K 2 - 1) / (110 - 10) 7 2 = 13.47 μH.

The meaning of the formula is clear, let's add 7 - the upper limit of the range, expressed in MHz. Selecting the coil core. At the frequencies of the range at the core, the magnetic permeability is M = 100, we choose the ferrite grade 100NN. We take a standard core 80 mm long and 8 mm in diameter. The ratio l / d = 80/8 = 10. From the reference books, we extract the effective value of the magnetic permeability md. It turns out 41.

We find the winding diameter D = 1.1 d = 8.8, the number of winding turns is determined by the formula:

W = √ (L / L1) D md mL pL qL;

we read the coefficients of the formula visually, using the graphs below. The figures will show the reference numbers used above. Look for the brand of ferrite, man does not live by bread alone. D is expressed in centimeters. The authors received: L1 = 0.001, mL = 0.38, pL = 0.9. qL is calculated using the formula:

qL = (d / D) 2 = (8 / 8.8) 2 = 0.826.

We substitute the numbers into the final expression for calculating the number of turns of the ferrite HF antenna, it turns out:

W = √ (13.47 / 0.001) x 0.88 x 41 x 0.38 x 0.9 x 0.826 = 373 turns.

The cascade must be connected to the first amplifier of the receiver, bypassing the input circuit. Let's say more, now we have calculated the means of selectivity in the 3.7-7 MHz range. In addition to the antenna, it turns on the input circuit of the receiver simultaneously. Therefore, it will be necessary to calculate the inductance of communication with the amplifier, fulfilling the conditions for ensuring selectivity (we take typical values).

Lw = (der - d) Rin / 2 π fmin K 2 = (0.04 - 0.01) 1000/2 x 3.14 x 3.7 x 3.61 = 0.35 μH.

The transformation ratio will be m = √ 0.35 / 13.47 = 0.16. We find the number of turns of the communication coil: 373 x 0.16 = 60 turns. We wind the antenna with a PEV-1 wire with a diameter of 0.1 mm, we wind the coil with a PELSHO with a diameter of 0.12 mm.

Many people are probably interested in several questions. For example, the purpose of Co is the formula for calculating a variable capacitor. The author shyly avoids the question, supposedly the initial capacity of the circuit. Hardworking readers will calculate the resonant frequencies of a parallel circuit in which an initial capacitance of 30 pF is soldered. We make a slight mistake by recommending placing a 30 pF trimmer next to the variable capacitor. The chain is being fine-tuned. Beginners are interested in the electrical circuit, which will include a homemade HF antenna ... A parallel circuit, the signal from which is removed by a transformer, is formed by wound coils. The core is common.

An independent HF antenna is ready. You will find this in a tourist receiver (models with a dynamo are popular today). Antennas in the HF range (and even more so in the CB) would be great if the structure was made in the form of a typical vibrator. Such designs are not used in portable equipment. The simplest HF antennas take up a lot of space. The welcome is better. The purpose of the HF antenna is to improve the signal quality. In the apartment, loggia. They told how to make a miniature HF antenna. Use vibrators in the country, in the field, in the forest, in an open area. Material provided by the design guide. The book is full of mistakes, and the result seems to be bearable.

Even old textbooks are guilty of typos missed by editors. It concerns more than one branch of radio electronics.

Today, when most of the old housing stock has been privatized, and the new one is certainly private property, it becomes increasingly difficult for the radio amateur to install full-size antennas on the roof of his house. The roof of a residential building is part of the property of every inhabitant of the house where they live, and they will never allow you to walk on it again, and even more so to install some kind of antenna and spoil the facade of the building. Nevertheless, today there are such cases when a radio amateur enters into an agreement with a housing department for the lease of a part of the roof with his antenna, but this requires additional financial resources and this is a completely different topic. Therefore, many novice radio amateurs can afford only those antennas that can be installed on a balcony or loggia, risking a reprimand from the house manager for damaging the facade of the building with an absurd bulging structure.

Pray to God that some "know-it-all activist" does not give a hint about the harmful radiation of the antenna, as from cellular antennas. Unfortunately, it must be admitted that for radio amateurs a new era of secrecy of their hobby and their HF antennas has begun, despite the paradox of their legality in the legal aspect of this issue. That is, the state allows broadcasting on the basis of the "Law on Communications of the Russian Federation", and the levels of permitted power correspond to the standards for HF radiation SanPiN 2.2.4 / 2.1.8.055-96, but they have to be invisible in order to avoid pointless evidence of the legality of their activities.

The proposed material will help the radio amateur to understand the antennas with a large shortening, capable of being placed in the space of a balcony, loggia, on the wall of a residential building or in a limited antenna field. The article "Balcony HF Antennas for Beginners" provides an overview of the options for antennas by different authors, previously published both in paper and in electronic form, and selected for the conditions of their installation in a limited space.

The explanatory comments will help the beginner understand how the antenna works. The presented materials are aimed at novice radio amateurs to acquire skills in building and choosing mini-antennas.

1. Dipole Hertz.
2. Shortened Hertzian dipole.
3. Spiral antennas.
4. Magnetic antennas.
5. Capacitive antennas.

1. Hertz's dipole

The most classic type of antenna is undeniably the Hertz dipole. This is a long wire, most often with a half-wave antenna width. Antenna wire has its own capacitance and inductance, which are distributed over the entire antenna web, they are called distributed antenna parameters. The capacitance of the antenna creates the electric component of the field (E), and the inductive component of the antenna, the magnetic field (H).

The classic Hertzian dipole by its nature has an impressive size and is half a long wave. Judge for yourself, at a frequency of 7 MHz, the wavelength is 300/7 = 42.86 meters, and half a wave will be 21.43 meters! Important parameters of any antenna are its characteristics from the side of space, these are its aperture, radiation resistance, effective antenna height, radiation pattern, etc., as well as from the side of the feeding feeder, these are input impedance, the presence of reactive components and the interaction of the feeder with the emitted wave. A half-wave dipole is a widespread linear emitter in the practice of antenna technology. However, any antenna has its own advantages and disadvantages.

Immediately, we note that for good operation of any antenna, at least two conditions are required, this is the presence of an optimal bias current and effective formation of an electromagnetic wave. HF antennas can be either vertical or horizontal. By installing a half-wave dipole vertically, and reducing its height by turning the fourth part into counterweights, we get the so-called quarter-wave vertical. Vertical quarter-wave antennas, for their effective operation, require a good "radio-technical ground", tk. the soil of the planet "Earth" has poor conductivity. Radio engineering ground is replaced by connecting counterweights. Practice shows that the minimum required number of counterweights should be about 12, but it is better if their number exceeds 20 ... 30, and ideally it is necessary to have 100-120 counterweights.

It should never be forgotten that an ideal vertical antenna with a hundred counterweights has an efficiency of 47%, and an antenna with three counterweights has an efficiency of less than 5%, which is clearly reflected in the graph. The power supplied to an antenna with a small number of counterweights is absorbed by the earth's surface and surrounding objects, heating them. The same low efficiency is expected from a low horizontal vibrator. Simply put, the earth reflects poorly and absorbs well the radiated radio wave, especially when the wave has not yet been formed in the near zone from the antenna, like a clouded mirror. The sea surface reflects better and the sandy desert does not reflect at all. According to the theory of reciprocity, the parameters and characteristics of the antenna are the same for both reception and transmission. This means that in the receiving mode at the vertical with a small number of counterweights, there is a large loss of the useful signal and, as a consequence, an increase in the noise component of the received signal.

Counterweights of a classic vertical should be at least as long as the main pin, i.e. the displacement currents flowing between the pin and the counterweights occupy a certain volume of space, which is involved not only in the formation of the directional diagram, but also in the formation of the field strength. With a greater approximation, we can say that each point on the pin corresponds to its own mirror point on the counterweight, between which displacement currents flow. The fact is that displacement currents, like all ordinary currents, flow along the path of least resistance, which in this case is concentrated in a volume limited by the radius of the pin. The generated directional diagram will be the superposition (superposition) of these currents. Returning to the above, this means that the efficiency of a classical antenna depends on the number of counterweights, i.e. the more counterweights, the more bias current, the more efficient the antenna, THIS IS THE FIRST CONDITION for good antenna performance.

The ideal case is a half-wave vibrator located in an open space in the absence of absorbing soil, or a vertical located on a solid metal surface with a radius of 2-3 wavelengths. This is necessary so that the soil of the earth or objects surrounding the antenna do not interfere with the effective formation of an electromagnetic wave. The fact is that the formation of a wave and the phase coincidence of the magnetic (H) and electric (E) components of the electromagnetic field occurs not in the near zone of the Hertz dipole, but in the middle and far zone at a distance of 2-3 wavelengths, THIS IS THE SECOND CONDITION for good work antennas. This is the main disadvantage of the classical Hertzian dipole.

The generated electromagnetic wave in the far zone is less susceptible to the influence of the earth's surface, bends around it, is reflected and propagates in the medium. All of the above very brief concepts are needed in order to understand the further essence of the construction of amateur balcony antennas, to look for such an antenna construct in which the wave is formed inside the antenna itself.

It is now clear that the placement of full-size antennas, a quarter-wave pole with counterweights or a half-wave Hertzian dipole in the HF band is almost impossible to place within a balcony or loggia. And if the radio amateur managed to find an accessible antenna attachment point on the building opposite to the balcony or window, then today it is considered great luck.

2. Shortened Hertz dipole.

With limited space at their disposal, the radio amateur has to compromise and reduce the size of the antennas. Antennas are considered electrically small if their dimensions do not exceed 10 ... 20% of the wavelength λ. In such cases, a shortened dipole is often used. When the antenna is shortened, its distributed capacitance and inductance decrease, respectively, its resonance changes towards higher frequencies. To compensate for this deficiency, additional inductors L and capacitive loads C are introduced into the antenna as lumped elements (Fig. 1).

The maximum antenna efficiency is achievable by placing the extension coils at the ends of the dipole, since the current at the ends of the dipole is maximum and distributed more evenly, which ensures the maximum effective antenna height hd = h. Turning on the inductors closer to the center of the dipole will reduce its own inductance, in this case, the current to the ends of the dipole drops, the effective height decreases, and then the antenna efficiency.

What is a capacitive load in a shortened dipole for? The fact is that with a large shortening, the quality factor of the antenna increases greatly, and the bandwidth of the antenna becomes narrower than the radio amateur band. The introduction of capacitive loads increases the antenna capacity, reduces the Q-factor of the formed LC-circuit and expands its bandwidth to an acceptable level. A shortened dipole is tuned to the operating frequency in resonance either by inductors or by the length of the conductors and capacitive loads. This provides compensation for their reactances at the resonant frequency, which is necessary according to the conditions of coordination with the power feeder.

Note: Thus, we compensate for the necessary characteristics of the shortened antenna to match it with the feeder and space, but a decrease in its geometric dimensions ALWAYS leads to a decrease in its efficiency (efficiency).

One of the examples of calculating the extension coil of inductance was described in the magazine "Radio", number 5, 1999, where the calculation is carried out from the available emitter. Inductors L1 and L2 are located here at the feeding point of the quarter-wave dipole A and counterweight D (Fig. 2). This is a single band antenna.

You can also calculate the inductance of the shortened dipole on the site of the radio amateur RN6LLV - he gives a link to download a calculator that can help in calculating the lengthening inductance.

There are also branded shortened antennas (Diamond HFV5), which have a multi-band version, see Fig. 3, in the same place its electrical diagram.

Antenna operation is based on parallel connection of resonant elements tuned to different frequencies. When moving from one range to another, they practically do not affect each other. Inductors L1-L5 are extension coils, each designed for its own frequency range, just like capacitive loads (antenna extension). The latter have a telescopic design, and by changing their length they are able to adjust the antenna in a small frequency range. The antenna is very narrow band.

* Mini - antenna for a range of 27MHz, the author of which is S. Zaugolny. Let's consider its work in more detail. The author's antenna is located on the 4th floor of a 9-storey panel building in the window opening and is essentially a room antenna, although this version of the antenna will work better outside the perimeter of the window (balcony, loggia). As can be seen from the figure, the antenna consists of an oscillatory circuit L1C1 tuned to resonance to the frequency of the communication channel, and the communication coil L2 acts as a matching element with the feeder, Fig. 4.a. The main emitter here are capacitive loads in the form of wire frames with dimensions 300 * 300mm and a shortened symmetric dipole consisting of two pieces of wire 750mm each. Considering that a vertically located half-wave dipole would occupy a height of 5.5 m, then an antenna with a height of only 1.5 m is a very convenient option for placement in the window opening.

If we exclude the resonant circuit from the circuit and connect the coaxial cable directly to the dipole, then the resonant frequency will be in the range of 55-60 MHz. Based on this scheme, it is clear that the frequency-setting element in this design is an oscillatory circuit, and the antenna is shortened by 3.7 times and has not greatly reduced its efficiency. If this design uses an oscillatory circuit tuned to other more low frequencies HF range, of course, the antenna will work, but with much lower efficiency. For example, if such an antenna is tuned to 7 MHz of the amateur band, then the antenna shortening factor from half the wave of this range will be 14.3, and the antenna efficiency will drop even more (by the square root of 14), i.e. more than 200 times. But there is nothing to be done about this, you have to choose such an antenna design that would be as effective as possible. This design clearly shows that capacitive loads in the form of wire squares act as radiating elements here, and they would perform their functions if they were all-metal. The weak link here is the L1C1 oscillatory circuit, which must have a high Q-factor, and part of the useful energy in this design is uselessly spent inside the plates of the C1 capacitor. Therefore, an increase in the capacitance of the capacitor, although it reduces the resonance frequency, it also reduces the overall efficiency of this design. When designing this antenna for lower frequencies in the HF range, you should pay attention to the fact that at the resonant frequency L1 is maximum, and C1 is minimum, not forgetting that capacitive radiators are part of the resonant system as a whole. It is advisable to design the maximum overlap in frequency no more than 2, and the emitters were located as far as possible from the walls of the building. The balcony version of this antenna with camouflage from prying eyes is shown in Fig. 4.b. It was a similar antenna that was used for some time in the middle of the 20th century on military vehicles in the HF range with a tuning frequency of 2-12 MHz.

* Single-band variant "Non-dying Fuchs antenna"(21 MHz) is shown in Fig. 5.a. The 6.3 meter long (almost half-wave) pin is fed from the end by a parallel oscillatory circuit with the same high resistance. Mr. Fuchs decided that this is how the parallel oscillatory circuit L1C1 and the half-wave dipole agree with each other, the way it is ... As you know, the half-wave dipole is self-sufficient and works for itself, it does not need counterweights like a quarter-wave vibrator. The emitter (copper wire) can be placed in a plastic fishing rod. While working on the air, such a fishing rod can be moved out of the balcony railing and put back, but in winter this creates a number of inconveniences. A piece of wire of only 0.8 m is used as a "ground" for the oscillatory circuit, which is very convenient when placing such an antenna on a balcony. At the same time, this is an exceptional case when a flower pot can be used as grounding (just kidding). The inductance of the L2 resonant coil is 1.4 μH, it is made on a frame with a diameter of 48 mm and contains 5 turns of 2.4 mm wire with a pitch of 2.4 mm. As a resonant capacitor with a capacity of 40 pF, the circuit uses two pieces of RG-6 coaxial cable. The segment (C2 according to the scheme) is an unchanged part of the resonant capacitor with a length of no more than 55-60 cm, and a shorter segment (C1 according to the scheme) is used for fine tuning to resonance (15-20 cm). The L1 coupling coil in the form of one turn over the L2 coil is made with an RG-6 cable with a gap of 2-3 cm of its braid, and the SWR adjustment is carried out by moving this turn from the middle towards the counterweight.

Note: The Fuchs antenna works well only in the half-wave version of the emitter, which can be shortened like spiral antennas (read below).

* Multi-band balcony antenna option shown in Fig. 5 B. It was tested back in the 50s of the last century. Here the inductance acts as an extension coil in autotransformer mode. And the capacitor C1 at 14 MHz tunes the antenna into resonance. Such a pin requires a good grounding, which is difficult to find on the balcony, although for this option you can use an extensive network of heating pipes in your apartment, but it is not recommended to supply more than 50 W of power. The L1 inductor has 34 turns of 6mm diameter copper tube wound on a 70mm diameter frame. Taps from 2,3 and 4 turns. In the range of 21 MHz, the switch P1 is closed, P2 is open, In the range of 14 MHz, P1 and P2 are closed. At 7 MHz, the position of the switches is at 21 MHz. In the range of 3.5 MHz, P1 and P2 are open. Switch P3 determines the coordination with the feeder. In both cases, it is possible to use a rod of about 5m, then the rest of the emitter will hang to the ground. It is clear that the use of such antenna options should be higher than the 2nd floor of the building.

Not all examples of shortening dipole antennas are presented in this section; other examples of shortening a linear dipole will be presented below.

3. Spiral antennas.

Continuing the discussion of the topic of shortened balcony antennas, one cannot ignore the HF helical antennas. And of course, it is necessary to recall their properties, which have practically all the properties of a Hertzian dipole.

Any shortened antenna, the dimensions of which do not exceed 10-20% of the wavelength, are classified as electrically small antennas.

Features of small antennas:

1. The smaller the antenna, the less the ohmic loss should be in it. Small antennas assembled from thin wires cannot work effectively, since they experience increased currents, and the skin effect requires low surface resistances. This is especially true for antennas with radiator sizes significantly less than a quarter of the wavelength.
2. Since the field strength is inversely proportional to the size of the antenna, a decrease in the size of the antenna leads to an increase in very high field strengths near it, and with an increase in the input power leads to the appearance of the "St. Elmo's fire" effect.
3. The lines of force of the electric field of shortened antennas have a certain effective volume in which this field is concentrated. It has a shape close to an ellipsoid of revolution. In fact, this is the volume of the near quasi-static field of the antenna.
4. A small antenna with dimensions of λ / 10 or less has a Q-factor of about 40-50 and a relative bandwidth of no more than 2%. Therefore, in such antennas it is necessary to introduce an adjustment element within the same amateur band. Such an example is easy to observe with small magnetic antennas. Expanding the bandwidth reduces the efficiency of the antenna, therefore, you must always strive to increase the efficiency of ultra-small antennas in different ways.

* Reducing the size of a symmetric half-wave dipole led first to the appearance of extension coils (Fig. 6.a), and a decrease in its turn-to-turn capacitance and a maximum increase in efficiency led to the appearance of an inductance coil for the design of helical antennas with transverse radiation. The spiral antenna (Fig. 6.b.) is a shortened, coiled classical half-wave (quarter-wave) dipole with distributed inductances and capacitors along the entire length. The Q-factor of such a dipole has increased, and the bandwidth has become narrower.

To expand the bandwidth, a shortened spiral dipole, like a shortened linear dipole, is sometimes equipped with a capacitive load, Fig. 6.b.

Since in the calculations of single-vibration antennas, the concept of the effective antenna area (A eff.) Is practiced quite widely, we will consider the possibilities of increasing the efficiency of spiral antennas using end disks (capacitive load) and refer to the graphical example of the distribution of currents in Fig. 7. Due to the fact that in a classical helical antenna the inductance coil (rolled antenna web) is distributed along the entire length, the current distribution along the antenna is linear, and the current area increases insignificantly. Where, Iap is the antinode current of the spiral antenna, Fig. 7.a. And the effective area of ​​the antenna Aeff. determines that part of the plane wave front area from which the antenna picks up energy.

To expand the bandwidth and increase the effective radiation area, the installation of end discs is practiced, which increases the efficiency of the antenna as a whole, Fig. 7.b.

When it comes to single-ended (quarter-wave) helical antennas, you should always remember that Aeff. highly dependent on the quality of the land. Therefore, you should know that the same efficiency of a quarter-wave vertical is provided by four counterweights with a length of λ / 4, six counterweights with a length of λ / 8 and eight counterweights with a length of λ / 16. Moreover, twenty λ / 16 counterweights provide the same efficiency as eight λ / 4 counterweights. It becomes clear why balcony radio amateurs came to the half-wave dipole. It works for itself (see Fig. 7.c.), The lines of force are closed to their elements and "ground", as in the structures in Fig. 7.a; b. he doesn't need it. In addition, spiral antennas can also be equipped with lumped elements of extension-L (or shortening-C) of the electrical length of the spiral radiator, and their spiral length can differ from the full-size spiral. An example of this is a variable capacitor (to be discussed below), which can be considered not only as a tuning element for a sequential oscillatory circuit, but also as a shortening element. There is also a spiral antenna for portable stations in the 27 MHz range (Fig. 8). There is a short coil extension inductor here.

* Compromise solution can be seen in the design of Valery Prodanov (UR5WCA), - a balcony spiral antenna 40-20m with a shortening factor K = 14, is quite worthy of attention of radio amateurs without a roof, see Fig. 9.

Firstly, it is multi-band (7/10/14 MHz), and secondly, to increase its efficiency, the author doubled the number of spiral antennas and connected them in phase. The absence of capacitive loads in this antenna is due to the fact that the expansion of the bandwidth and Aeff. The antenna is achieved by in-phase connection of two identical radiation elements in parallel. Each antenna is wound with copper wire on a PVC pipe with a diameter of 5 cm, the length of the wire of each antenna is half a wave for the 7 MHz band. Unlike the Fuchs antenna, this antenna is matched to the feeder by means of a broadband transformer. Transformer outputs 1 and 2 have common-mode voltage. Vibrators in the author's version stand from each other at a distance of only 1m, this is the width of the balcony. With the expansion of this distance within the balcony, the gain will increase slightly, but the bandwidth of the antenna will expand significantly.

* Amateur radio Harry Elington(WA0WHE, source "QST", 1972, January. Fig. 8.) built an 80m spiral antenna with a shortening factor of about K = 6.7, which in its garden can be disguised as the support of a night lantern or flagpole. As you can see from his commentary, foreign radio amateurs also care about their relative peace of mind, although the antenna is installed in a private courtyard. According to the author, a spiral antenna with a capacitive load on a pipe with a diameter of 102 mm, a height of about 6 meters and a counterweight of four wires easily reaches an SWR of 1.2-1.3, and with SWR = 2 it works in a bandwidth of up to 100 kHz. The electrical length of the wire in the spiral was also half a wave. The half-wave antenna is powered from the end of the antenna through a coaxial cable with a characteristic impedance of 50 Ohm through a KPE -150pF, which turned the antenna into a series oscillatory circuit (L1C1) with a radiating coil inductance.

Of course, in transmission efficiency, the vertical spiral is inferior to the classical dipole, but according to the author, this antenna is much better in reception.

* Rolled up antennas

To reduce the size of a linear half-wave dipole, it is not necessary to twist it into a spiral.

In principle, the spiral can be replaced by other forms of folding of a half-wave dipole, for example, according to Minkowski, Fig. 11. A dipole with a fixed frequency of 28.5 MHz can be placed on a substrate with dimensions of 175mm x175mm. But fractal antennas are very narrowband, and for radio amateurs they are only of cognitive interest in transforming their designs.

Using another method of shortening the size of the antennas, the half-wave vibrator, or the vertical, can be shortened by squeezing it into a meander shape, Fig. 12. At the same time, the parameters of an antenna such as a vertical or a dipole change insignificantly when they are compressed by no more than half. When the horizontal and vertical parts of the meander are equal, the gain of the meander antenna is reduced by about 1 dB, and the input impedance is close to 50 Ohm, which makes it possible to feed such an antenna directly with a 50-ohm cable. A further reduction in size (NOT the length of the wire) leads to a decrease in the gain and input impedance of the antenna. However, the performance of a meander antenna for shortwave range is characterized by an increased radiation resistance relative to linear antennas with the same shortening of the wire. Experimental studies have shown that with a meander height of 44 cm and with 21 elements at a resonant frequency of 21.1 MHz, the antenna impedance was 22 Ohm, while a linear vertical of the same length has an impedance 10-15 times less. Due to the presence of horizontal and vertical sections of the meander, the antenna receives and emits electromagnetic waves of both horizontal and vertical polarization.

By squeezing or stretching it, you can achieve the antenna resonance at the desired frequency. The meander step can be 0.015λ, but this parameter is not critical. Instead of a meander, you can use a conductor with triangular bends or a spiral. The required length of the vibrators can be determined experimentally. As a starting point, we can assume that the length of the "straightened" conductor should be about a quarter of the wavelength for each arm of the split vibrator.

* "Tesla Spiral" in the balcony antenna. Following the cherished goal of reducing the size of the balcony antenna and minimizing losses in Aeff, radio amateurs instead of end disks began to use a more technologically advanced flat Tesla spiral than the meander, using it as an extension of the inductance of the shortened dipole and the end capacitance at the same time (Fig. 6. but.). The distribution of magnetic and electric fields in a flat Tesla inductor is shown in Fig. 13. This corresponds to the theory of radio wave propagation, where the E-field and the H-field are mutually perpendicular.

There is also nothing supernatural in antennas with two flat Tesla spirals, and therefore the rules for constructing a Tesla spiral antenna remain classic:

• the electrical length of the spiral can be an antenna with an unbalanced power supply, either a quarter-wave vertical or a folded half-wave dipole.
• The larger the winding step and the larger its diameter, the higher its efficiency and vice versa.
• The greater the distance between the ends of the folded half-wave vibrator, the higher its efficiency, and vice versa.

In a word, we got a rolled half-wave dipole in the form of flat inductors at its ends, see Fig. 14. To what extent to reduce or increase this or that structure, the radio amateur decides after going out onto his balcony with a tape measure (after agreement with the last instance, with his mother or wife).

Using a flat inductor with large gaps between the turns at the ends of the dipole, two problems are solved at once. This is the compensation of the electrical length of the shortened vibrator by the distributed inductance and capacitance, as well as the increase in the effective area of ​​the shortened antenna Aeff, and the expansion of its bandwidth simultaneously, as in Fig. 7.b.c. This solution simplifies the design of the shortened antenna and allows all dispersed LC antenna elements to operate at maximum efficiency. There are no non-working antenna elements, for example, as a capacitance in magnetic ML-antennas, and inductance in EH-antennas. It should be remembered that the skin effect of the latter requires thick and highly conductive surfaces, but considering an antenna with a Tesla inductor, we see that a coiled antenna repeats the electrical parameters of a conventional half-wave vibrator. In this case, the distribution of currents and voltages along its entire length of the antenna web is subject to the laws of a linear dipole and remains unchanged with some exceptions. Therefore, the need to thicken the antenna elements (Tesla spiral) completely disappears. In addition, power is not consumed for heating the antenna elements. The facts listed above make you think about the high budget of this design. And the simplicity of its manufacture from the hand to someone who at least once in his life held a hammer in his hands and bandaged his finger.

Such an antenna with some interference can be called inductively capacitive, in which there are LC radiation elements, or a Tesla spiral antenna. In addition, taking into account the near field (quasi-static) theoretically can give even higher values ​​of the strengths, which is confirmed by field tests of this design. The EH-field is created in the body of the antenna and, accordingly, this antenna is less dependent on the quality of the ground and surrounding objects, which in fact is a godsend for the family of balcony antennas. It is no secret that such antennas have long existed among radio amateurs, and this publication provides material on transforming a linear dipole into a spiral antenna with transverse radiation, then into a shortened antenna with the code name "Tesla spiral". A flat spiral can be wound with a wire of 1.0-1.5mm, because at the end of the antenna there is high voltage, and the current is minimal. A wire with a diameter of 2-3mm will slightly improve the efficiency of the antenna, but it will significantly drain your wallet.

Note: The design and manufacture of shortened antennas of the "spiral" and "Tesla spiral" type with electrical length λ / 2 compares favorably with a spiral with electrical length λ / 4 due to the lack of good ground on the balcony.

Antenna power supply.

We consider an antenna with Tesla spirals as a symmetrical half-wave dipole coiled into two parallel spirals at its ends. Their planes are parallel to each other, although they can be in the same plane, Fig. 14. Its input impedance is only slightly different from the classic version, so the classic matching options are applicable here.

Linear Windom antenna see Fig. 15. refers to vibrators with unbalanced power supply, it is distinguished by its "unpretentiousness" in terms of matching with the transceiver. The uniqueness of the Windom antenna lies in its multi-band application and ease of manufacture. Converting this antenna into "Tesla spirals", in space, the symmetrical antenna will look like in Fig. 16.а, - with gamma-matching, and an asymmetric dipole Windom, fig.16.b.

To decide which antenna option to choose for the implementation of your plans to turn your balcony into an "antenna field" is better to read this article to the end. The design of balcony antennas compares favorably with full-size antennas in that their parameters and other combinations can be made without going to the roof of your house and not injuring the house manager once again. In addition, this antenna is a practical guide for novice radio amateurs, when you can practically "on your knees" learn all the basics of building elementary antennas.

Assembling the antenna

Based on practice, it is better to take the length of the wire that makes up the antenna web with a small margin, slightly larger by 5-10% of its estimated length, it should be an insulated single-core copper wire for wiring with a diameter of 1.0-1.5 mm. The supporting structure of the future antenna is assembled (by soldering) from PVC heating pipes. Of course, in no case should pipes with a reinforced aluminum pipe be used. Dry wooden sticks are also suitable for the experiment, see Fig. 17.

The Russian radio amateur does not need to tell the step-by-step assembly of the supporting structure, he just needs to look at the original product from afar. Nevertheless, when assembling a Windom antenna or a symmetrical dipole, it is worth first marking the calculated power point on the canvas of the future antenna and fixing it in the middle of the traverse, where the antenna will be powered. Naturally, the length of the traverse is included in the total electrical size of the future antenna, and the longer it is, the higher the antenna efficiency.

Transformer

The impedance of the symmetrical dipole antenna will be slightly less than 50 Ohm, therefore, see the connection diagram in Fig. 18.a. can be arranged by simply turning on the magnetic latch or using gamma matching.

The resistance of the rolled antenna "Windom" has a little less than 300 Ohm, so you can use the data in Table 1, which captivates with its versatility with the use of just one magnetic latch.

The ferrite core (latch) must be tested before installation on the antenna. For this, the secondary L2 is connected to the transmitter, and the primary L1 to the antenna equivalent. Check the SWR, core heating, as well as the power loss in the transformer. If the core heats up at a given power, then the number of ferrite latches must be doubled. If there is an unacceptable loss in power, then ferrite must be selected. See Table 2 for the power loss to dB ratio.

As convenient as ferrite is, I still believe that for the radiated radio wave of any mini-antenna, where a huge EH-field is concentrated, it is a "black hole". The close location of the ferrite reduces the efficiency of the mini-antenna by a factor of µ / 100, and all attempts to make the antenna as efficient as possible are in vain. Therefore, in mini-antennas, the greatest preference is given to air-core transformers, Fig. 18.b. Such a transformer, operating in the range of 160-10 m, is wound with a double wire 1.5 mm on a frame with a diameter of 25 and a length of 140 mm, 16 turns with a winding length of 100 mm.

It is also worth remembering that the feeder of such an antenna experiences a high intensity of the radiated field on its braid and creates a voltage in it, which negatively affects the operation of the transceiver in the transmission mode. It is better to eliminate the antenna effect with a locking feeder-choke without using ferrite rings, see Fig. 19. These are 5-20 turns of coaxial cable, wound on a frame with a diameter of 10-20 centimeters.

Such feeder chokes can be installed in the immediate vicinity of the antenna web (body), but it is better to go beyond the high field concentration limit and install at a distance of about 1.5-2 m from the antenna web. A second such choke, installed at a distance of λ / 4 from the first, will not interfere.

Antenna tuning

Tuning the antenna brings great pleasure, and moreover, such a construct is recommended to be used for laboratory work in specialized colleges and universities, without leaving the laboratory, on the topic "Antennas".

Tuning can be started by searching for the resonance frequency and tuning the antenna SWR. It consists in moving the antenna feed point to one side or the other. There is no need to move the transformer or the supply cable along the traverse and mercilessly cut the wires to clarify the power point. Everything here is close and simple.

It is enough to make sliders in the form of "crocodiles" at the inner ends of the flat spirals on one side and on the other, as shown in Fig.20. Having previously provided for a slightly increase in the length of the spiral, taking into account the settings, we move the sliders from different sides of the dipole to the same length, but in opposite directions, thereby we move the power point. The result of the tuning will be the expected SWR of no more than 1.1-1.2 at the found frequency. Reactive components should be kept to a minimum. Of course, like any antenna, it should be in a place as close as possible to the conditions of the installation site.

The second stage will be tuning the antenna exactly into resonance, this is achieved by shortening or lengthening the vibrators on both sides into equal pieces of wire with the same sliders. That is, you can increase the tuning frequency by shortening both turns of the spiral by the same size, and reduce the frequency, on the contrary, by lengthening. After completing the tuning at the future installation site, it is necessary to reliably connect, isolate and fix all antenna elements.

Antenna gain, bandwidth and beam angle

According to practicing radio amateurs, this antenna has a lower radiation angle of about 15 degrees than a full-size dipole and is more suitable for DX communications. The Tesla spiral dipole has an attenuation of -2.5 dB relative to a full-size dipole mounted at the same height from the ground (λ / 4). The bandwidth of the antenna at the level of -3 dB is 120-150 kHz! When placed horizontally, the described antenna has an eightfold radiation pattern similar to that of a full-size half-wave dipole, and the minima of the radiation pattern provide attenuation of up to -25 dB. The antenna efficiency can be improved, as in the classic version, by increasing the placement height. But when the antennas are placed in the same conditions at heights of λ / 8 and below, the Tesla spiral antenna will be more effective than a half-wave dipole.

Note: All these Tesla spiral antennas look perfect, but even if such an antenna layout is worse than a dipole by 6 dB, i.e. one point on the S-meter, that's great.

Other antenna constructs.

With a dipole for a range of 40 meters and with other designs of dipoles up to a range of 10m, everything is now clear, but let's return to the spiral vertical for a range of 80m (Fig. 10.). Here, preference is given to a half-wave helical antenna, and therefore "ground" is only needed nominally.

The power supply of such antennas can be carried out as in Fig. 9 by means of a summing transformer or in Fig. 10. variable capacitor. Of course, in the second case, the antenna bandwidth will be much narrower, but the antenna has the ability to tune in the range and yet, according to the copyright information, at least some kind of grounding is required. Our task is to get rid of it while on the balcony. Since the antenna is powered from the end (at the voltage "antinode"), the input impedance of a shortened half-wave helical antenna can be about 800-1000 ohms. This value depends on the height of the vertical part of the antenna, on the diameter of the "Tesla spiral" and on the location of the antenna relative to surrounding objects. To match the high input impedance of the antenna with a low impedance of the feeder (50 Ohm), you can use a high-frequency autotransformer in the form of an inductor with a tap (Fig. 21.a), which is widely practiced in half-wave, vertically arranged linear antennas at 27 MHz by SIRIO, ENERGY, etc.

Data of the matching autotransformer for a half-wave antenna C-Bi of the 10-11m range:

D = 30mm; L1 = 2 turns; L2 = 5 turns; d = 1.0mm; h = 12-13 mm. Distance between L1 and L2 = 5mm. The coils are wound on one plastic frame coil to coil. The cable is connected with a central core to a 2-turn tap. The web (end) of the half-wave vibrator is connected to the "hot" lead of the L2 coil. The power for which the autotransformer is designed is up to 100 W. Possible selection of the retraction of the coil.

Data of the matching autotransformer for a half-wave antenna of the spiral type 40m range:

D = 32mm; L1 = 4.6μH; h = 20 mm; d = 1.5mm; n = 12 turns. L2 = 7.5μH; ; h = 27 mm; d = 1.5mm; n = 17 turns. The coil is wound on one plastic frame. The cable is connected with the central core to the tap. The antenna web (end of the helix) is connected to the hot lead of the L2 coil. The power for which the autotransformer is designed is 150-200W. Possible selection of the retraction of the coil.

Dimensions of the antenna "Tesla spiral" range 40m:the total length of the wire is 21m, the traverse is 0.9-1.5m high with a diameter of 31mm, on radially mounted spokes, 0.45m each. The outer diameter of the spiral will be 0.9m

Data of the matching autotransformer for the spiral antenna of the 80m range: D = 32mm; L1 = 10.8μH; h = 37 mm; d = 1.5mm; n = 22 turns. L2 = 17.6μH; ; h = 58 mm; d = 1.5mm; n = 34 turns. The coil is wound on one plastic frame. The cable is connected with the central core to the tap. The antenna web (end of the helix) is connected to the hot lead of the L2 coil. Possible selection of the retraction of the coil.

Dimensions of the antenna "Tesla spiral" range of 80m:the total length of the wire is 43m, the traverse is 1.3-1.5m high with a diameter of 31mm, on the radially installed spokes of 0.6m. The outer diameter of the spiral will be 1.2m

Matching with a half-wave spiral dipole when powered from the end can be carried out not only by means of an autotransformer, but also according to Fuchs, a parallel oscillatory circuit, see Fig. 5.a.

Note:

• When feeding a half-wave antenna from one end, tuning to resonance can be done from either end of the antenna.
• In the absence of at least some kind of grounding, a locking feeder-choke must be installed on the feeder.

Vertical directional antenna option

Having a pair of Tesla spiral antennas and some area to place them, you can create a directional antenna. Let me remind you that all operations with this antenna are completely identical with linear antennas, and the need to roll them up is not due to the fashion for mini-antennas, but to the lack of locations for linear antennas. The use of two-element directional antennas with a distance of 0.09-0.1λ between them allows you to design and build a directional Tesla spiral antenna.

This idea is taken from "KB JOURNAL" No. 6 for 1998. This antenna is perfectly described by Vladimir Polyakov (RA3AAE), which can be found on the Internet. The essence of the antenna is that two vertical antennas located at a distance of 0.09λ are fed in antiphase by one feeder (one with a braid, the other with a central core). Power is produced like the same Windom antenna, only with a single-wire power supply, Fig. 22 .. The phase shift between opposite antennas is created by tuning them lower and higher in frequency, as in classic directional Yagi antennas. And the coordination with the feeder is carried out by simply moving the feed point along the web of both antennas, moving away from the zero feed point (the middle of the vibrator). When you move the power point from the middle for a certain distance X, you can achieve resistance from 0 to 600 ohms, as in the Windom antenna. We only need a resistance of about 25 ohms, so the displacement of the feed point from the middle of the vibrators will be very small.

The electrical diagram of the proposed antenna with approximate dimensions given in wavelengths is shown in Fig. 22. And the practical tuning of the Tesla spiral antenna to the required load resistance is quite feasible according to the technology in Fig.20. The antenna is powered at points XX directly by a feeder with a characteristic impedance of 50 Ohm, and its braid must be isolated with a blocking feeder-choke, see Fig. 19.

30m vertical directional helix antenna option according to RA3AAE

If, for some reason, the radio amateur is not satisfied with the "Tesla spiral" antenna option, then the version of the antenna with spiral radiators is quite feasible, Fig. 23. Let's give its calculation.

We use the length of the helix wire half a wave:

λ = 300 / MHz = 300 / 10.1; λ / 2 -29.7 / 2 = 14.85. Let's take 15m

Let's calculate the pitch on the coils on a pipe with a diameter of 7.5 cm, the length of the coil winding = 135 cm:

Circumference L = D * π = -7.5cm * 3.14 = 23.55cm. = 0.2355m;

number of turns of a half-wave dipole -15m / 0.2355 = 63.69 = 64 turns;

the step of winding on a ruby ​​with a length of 135cm. - 135cm. / 64 = 2.1cm ..

Answer: on a pipe with a diameter of 75 mm we wind 15 meters of copper wire with a diameter of 1-1.5 mm in the amount of 64 turns with a winding step = 2 cm.

The distance between the same vibrators will be 30 * 0.1 = 3m.

Note: the antenna calculations were rounded off for the possibility of shortening the winding wire during tuning.

To increase the bias current and ease of adjustment, it is necessary to make small adjustable capacitive loads at the ends of the vibrators, and a locking-feeder-choke must be put on the feeder, at the connection point. The displaced feed points correspond to the dimensions in Fig. 22. It should be remembered that unidirectionality in this design is achieved by a phase shift between opposite spirals by tuning them with a difference of 5-8% in frequency, as in classical directional Uda-Yagi antennas.

Rolled up "Bazooka"

As you know, the noise environment in any city leaves much to be desired. This also applies to the frequency radio spectrum due to the tatal use of switching power converters for household appliances. For this reason, I made an attempt to use in the antenna "Tesla spiral" a well-proven antenna of the "Bazooka" type. In principle, this is the same half-wave vibrator with a closed-loop system as all loop antennas. It was not difficult to place it on the traverse presented above. The experiment was carried out at a frequency of 10.1 MHz. A 7mm TV cable was used as the antenna web. (fig. 24). The main thing is that the braid of the cable is not aluminum like its sheath, but copper.

Even experienced radio amateurs "pierce" on this, taking a gray cable braid for tinned copper when buying. Since we are talking here is a QRP antenna for a balcony, and the input power is up to 100 W, then such a cable will be quite suitable. The shortening factor of such a cable with foamed polyethylene is about 0.82. Therefore, the length of L1 (Fig. 25) for a frequency of 10.1 MHz. It was 7.42 cm each, and the length of the extension conductors L2 with this antenna arrangement was 1.83 cm each. The input resistance of the folded "Bazooka" after mounting in an open area was about 22-25 ohms and is not regulated by anything. Therefore, a 1: 2 transformer was required here. In the trial version, it was made on a ferrite latch with simple wires from speakers with the ratio of turns according to Table 1. Another version of the 1: 2 transformer is shown in Fig. 26.

Aperiodic broadband antenna "Bazooka"

Not a single radio amateur who even has an antenna field at his disposal on the roof of his house or in the courtyard of the cottage will not give up the observation broadband antenna on the basis of a Tesla coiled feeder. The classic version of an aperiodic antenna with a load resistor is known to many, here the Bazooka antenna plays the role of a broadband vibrator, and its bandwidth, as in the classical versions, has a large overlap towards higher frequencies.

The antenna diagram is shown in Fig. 27, and the power of the resistor is about 30% of the power supplied to the antenna. If the antenna is used only as a receiving antenna, the power of the 0.125W resistor is sufficient. It should be noted that the "Tesla spiral" antenna, installed horizontally, has an eight-fold directional pattern and is capable of spatial selection of radio signals. Installed vertically, it has a circular radiation pattern.

4. Magnetic antennas.

The second, no less popular type of antenna is an inductive radiator with shortened dimensions, this is a magnetic frame. The magnetic frame was discovered in 1916 by K. Brown and was used until 1942 as a receiving station in radio receivers and direction finders. This is also an open oscillatory circuit with a frame perimeter less than ≤ 0.25 wavelength, it is called “magnetic loop”, and its abbreviated name has acquired an abbreviation - ML. The active element of the magnetic loop is inductance. In 1942, an amateur radio operator using the radio call sign W9LZX first used such an antenna at the HCJB mission broadcast station in the mountains of Ecuador. Thanks to this, the magnetic antenna immediately conquered the amateur radio world and has since been widely used in amateur and professional communications. Magnetic loop antennas are one of the most interesting types of small-sized antennas that can be conveniently placed both on balconies and on window sills.

It takes the form of a loop of a conductor that is connected to a variable capacitor to achieve resonance, where the loop is the radiating inductance of an oscillatory LC circuit. The emitter here is only the inductance in the form of a loop. The dimensions of such an antenna are very small, and the frame perimeter is usually 0.03-0.25 λ. The maximum efficiency of the magnetic loop can reach 90% relative to the Hertz dipole, see Fig. 29.a. The capacitance C in this antenna does not participate in the radiation process and has a purely resonant nature, as in any oscillatory circuit, Fig. 29.b ..

Antenna efficiency strongly depends on the active resistance of the antenna web, on its dimensions, on placement in space, but to a greater extent on the materials used for the antenna design. The bandwidth of a loop antenna is usually from units to tens of kilohertz, which is associated with the high quality factor of the formed LC circuit. Therefore, the efficiency of an ML antenna largely depends on its Q-factor, the higher the Q-factor, the higher its efficiency. This antenna is also used as a transmitting antenna. With small dimensions of the frame, the amplitude and phase of the current flowing in the frame are practically constant along the entire perimeter. The maximum radiation intensity corresponds to the plane of the frame. In the perpendicular plane of the frame, the radiation pattern has a sharp minimum, and the overall pattern of the loop antenna has a figure of eight.

Electric field strength E electromagnetic wave (V / m) at a distance d from transmitting loop antenna, is calculated by the formula:

EMF E induced in foster loop antenna, is calculated by the formula:

The eight-fold directional pattern of the frame allows you to use its minima of the pattern in order to detune it in space from closely located interference or unwanted radiation in a certain direction in the near zones up to 100 km.

When manufacturing the antenna, it is required to observe the ratio of the diameters of the radiating ring and the communication loop D / d as 5/1. The coupling coil is made from a coaxial cable, is located in the immediate vicinity of the radiating ring on the opposite side from the capacitor, and looks like in Fig. 30.

Since a large current flows in the emitting frame, reaching tens of amperes, the frame in the frequency ranges 1.8-30 MHz is made of a copper tube with a diameter of about 40-20 mm, and the tuning capacitor in resonance should not have rubbing contacts. Its breakdown voltage must be at least 10 kV with a power input of up to 100 W. The diameter of the radiating element depends on the range of frequencies used and is calculated from the wavelength of the high-frequency part of the range, where the perimeter of the frame is P = 0.25λ, counting from the upper frequency.

Perhaps one of the first after W9LZX, German shortwave DP9IV with ML antenna installed on the window, with a transmitter power of only 5 W, in the 14 MHz band I made QSOs with many European countries, and with a power of 50 W - with other continents. It was this antenna that became the starting point for the experiments of Russian radio amateurs, see Fig. 31.

The desire to create an experimental compact indoor antenna, which can also be safely called an EH antenna, in close cooperation with Alexander Grachev ( UA6AGW), Sergey Tetyukhin (R3PIN) designed the next masterpiece, see Fig. 32.

It is this low-budget design of the room version of the EH antenna that can please the radio amateur-newcomer or summer resident. The antenna circuit includes both a magnetic emitter L1; L2 and a capacitive one in the form of a telescopic "whisker".

Particular attention in this design (R3PIN) deserves a resonant system for matching the feeder with the antenna Lw; C1, which once again increases the Q-factor of the entire antenna system and allows you to slightly raise the antenna gain as a whole. As the primary circuit together with the "mustache", as in the design of Yakov Moiseevich, the braid of the cable of the antenna canvas acts here. With the length of these "whiskers" and their position in space, it is easy to achieve resonance and the most effective operation of the antenna as a whole by the current indicator in the frame. And the provision of the antenna with an indicator device allows us to consider this version of the antenna as a completely finished construct. But whatever the design of magnetic antennas, you always want to increase its efficiency.

Dual-loop magnetic antennas in the form of an eight, relatively recently began to appear among radio amateurs, see Fig. 33. Its aperture is twice as large as the classical one. The capacitor C1 can change the resonance of the antenna with frequency overlap by 2-3 times, and the total perimeter of the circumference of the two loops is ≤ 0.5λ. This is comparable to a half-wave antenna, and its small radiation aperture is compensated by an increased Q factor. It is better to match the feeder with such an antenna by means of inductive coupling.

Theoretical digression: The double loop can be considered as a mixed oscillatory system of LL and LC systems. Here, for normal operation, both arms are loaded on the radiation medium synchronously and in phase. If a positive half-wave is fed to the left shoulder, then exactly the same wave is fed to the right shoulder. The EMF of self-induction generated in each arm will, according to Lenz's rule, be opposite to the EMF of induction, but since the EMF of induction of each arm is opposite in direction, the EMF of self-induction will always coincide with the direction of induction of the opposite arm. Then the induction in the L1 coil will be summed up with the self-induction from the L2 coil, and the induction of the L2 coil - with the L1 self-induction. Just as in the LC circuit, the total radiation power can be several times higher than the input power. Power can be supplied to any of the inductors and in any way.

The double border is shown in Fig. 33.a.

The design of a two-loop antenna, where L1 and L2 are connected to each other in the form of a figure of eight. This is how the two-frame ML was born. Let's call it conditionally ML-8.

The ML-8, unlike ML, has its own peculiarity - it can have two resonances, the oscillating circuit L1; C1 has its own resonant frequency, and L2; C1 has its own. The task of the designer is to achieve the unity of resonances and, accordingly, the maximum efficiency of the antenna, therefore, the dimensions of the loops L1; L2 and their inductances must be the same. In practice, an instrumental error of a couple of centimeters changes one or another inductance, the tuning frequencies of the resonances diverge somewhat, and the antenna receives a certain frequency delta. In addition, the double inclusion of identical antennas expands the bandwidth of the antenna as a whole. Sometimes constructors do this on purpose. In practice, ML-8 is actively used by radio amateurs with radio call signs RV3YE; US0KF; LZ1AQ; K8NDS and others unambiguously asserting that such an antenna works much better than a single-loop antenna, and changing its position in space can be easily controlled by spatial selection. Preliminary calculations show that for the ML-8 for a range of 40 meters, the diameter of each loop at maximum efficiency will be slightly less than 3 meters. It is clear that such an antenna can only be installed outdoors. And we dream of an effective ML-8 antenna for a balcony or even a windowsill. Of course, you can reduce the diameter of each loop to 1 meter and adjust the resonance of the antenna with the capacitor C1 to the required frequency, but the efficiency of such an antenna will drop by more than 5 times. You can go the other way, save the calculated inductance of each loop, using not one, but two turns in it, leaving the resonant capacitor with the same rating, respectively, and the quality factor of the antenna as a whole. There is no doubt that the antenna aperture will decrease, but the number of turns "N" will partially offset this loss, according to the formula below:

From the above formula, it can be seen that the number of turns N is one of the multipliers of the numerator and is in the same row, both with the area of ​​the turn-S and with its quality factor-Q.

For example, a radio amateur OK2ER(see Fig. 34) considered it possible to use a 4-turn ML with a diameter of only 0.8 m in the range of 160-40 m.

The author of the antenna reports that at 160 meters the antenna works nominally and is used more for radio surveillance. In the range of 40m. it is enough to use a jumper that halves the working number of turns. Let's pay attention to the materials used - the copper pipe of the loop is taken from water heating, the clips connecting them into a common monolith are used to install water supply plastic pipes, and a sealed plastic box was purchased at an electrician's store. The matching of the antenna with the feeder is capacitive, and is performed according to any of the presented schemes, see Fig. 35.

In addition to the above, we need to understand that the following antenna elements negatively affect the quality-Q of the antenna as a whole:

From the above formula, we see that the active resistance of the inductance Rk and the capacitance of the oscillatory system CK, standing in the denominator, should be minimal. That is why all MLs are made of copper pipe, as large as possible, but there are cases when the hinge sheet is made of aluminum. The quality factor of such an antenna and its efficiency drops by 1.1-1.4 times. With regard to the capacity of the oscillatory system, then everything is more complicated. With the same loop size L, for example, at a resonant frequency of 14 MHz, the capacitance C will be only 28 pF, and the efficiency = 79%. At a frequency of 7MHz, efficiency = 25%. Whereas at a frequency of 3.5 MHz with a capacitance of 610 pF, its efficiency = 3%. Therefore, ML is used most often for two ranges, and the third (lowest) is considered an overview. Therefore, it is necessary to make calculations based on the highest range with a minimum capacity C1.

Double magnetic antenna for a range of 20m.

The parameters of each loop will be as follows: If the diameter of the sheet (copper pipe) is 22mm, the diameter of the double loop is 0.7m, the distance between the turns is 0.21m, the inductance of the loop will be 4.01μH. The required design parameters of the antenna for other frequencies are summarized in Table 3.

Table 3.

Tuning frequency (MHz)	Capacitance C1 (pF)	Bandwidth (kHz)

In height, such an antenna will be only 1.50-1.60 m. That is quite acceptable for an antenna of the type - ML-8 balcony version and even an antenna hung outside the window of a residential multi-storey building. And its wiring diagram will look like in fig. 36.a.

Antenna power can be capacitively coupled or inductively coupled. Capacitive communication options shown in Fig. 35 can be selected at the request of the radio amateur.

The most budgetary option is inductive coupling, but its diameter will be different.

Calculation of the diameter (d) of the ML-8 tie loop is made from the calculated diameter of two loops.

The circumference of the two loops after recalculation is 4.4 * 2 = 8.8 meters.

Let's calculate the imaginary diameter of two loops D = 8.8m / 3.14 = 2.8 meters.

Let's calculate the diameter of the connection loop - d = D / 5. = 2.8 / 5 = 0.56 meters.

Since in this design we use a two-turn system, the communication loop must also have two loops. We twist it in half and we get a two-turn communication loop with a diameter of about 28 cm. The selection of communication with the antenna is carried out at the time of the SWR specification in the priority frequency range. The coupling loop can be galvanically coupled to the zero voltage point (Fig. 36.a.) and be located closer to it.

Electric emitter, this is another additional element of radiation. If the magnetic antenna emits an electromagnetic wave with the priority of the magnetic field, then the electric emitter will perform the function of an additional emitter of the electric field-E. In fact, it should replace the initial capacitance C1, and the drain current, which previously was uselessly passed between the closed plates of the capacitor C1, now operates on additional radiation. In this case, a fraction of the supplied power will be additionally emitted by electric emitters, Fig. 36.b. The bandwidth will increase to the limits of the amateur radio band as in the EH antennas. The capacity of such emitters is low (12-16pF, no more than 20), and therefore their efficiency in low-frequency ranges will be low. You can familiarize yourself with the operation of the EH antennas by following the links:

For tuning into resonance of a magnetic antenna, it is best to use vacuum capacitors with high breakdown voltage and high quality factor. Moreover, using a gearbox and an electric drive, the antenna can be tuned remotely.

We are designing a budget balcony antenna that you can approach at any time, change its position in space, rebuild or switch to a different frequency. If at points "a" and "b" (see Fig. 36.a.) Instead of a scarce and expensive variable capacitor with large gaps, you connect a capacitor made of sections of RG-213 cable with a linear capacity of 100 pF / m, then you can instantly change the frequency settings, and the tuning capacitor C1 to clarify the tuning resonance. The "condenser cable" can be rolled up and sealed in any of the ways. Such a set of capacities can be provided for each range separately, and can be connected to the circuit using a conventional electrical outlet (points a and b) paired with an electrical plug. Approximate capacities C1 by ranges are shown in table 1.

Antenna tuning indication in resonance it is better to do it directly on the antenna itself (this is clearer). To do this, it is enough not far from the communication coil on the L1 web (point of zero voltage) to wind tightly 25-30 turns of MGTF wire, and seal the setting indicator with all its elements from precipitation. The simplest diagram is shown in Fig. 37. The maximum readings of the device P will indicate a successful antenna tuning.

To the detriment of the antenna efficiency As the material of the loops L1; L2, you can use cheaper materials, for example, a PVC pipe with an aluminum layer inside for laying a water pipe with a diameter of 10-12 mm.

DDRR antenna

Despite the fact that the efficiency of the classical DDRR antenna is 2.5 dB inferior to the quarter-wave vibrator, its geometry turned out to be so attractive that DDRR was patented by Nortrop and put into mass production.

As in the case of the Groundplane, the main factor in the decent efficiency of the DDRR antenna is a solid counterweight. It is a flat metal disc with high surface conductivity. Its diameter must be at least 25% larger than the diameter of the ring conductor. The elevation angle of the main beam is the smaller, the higher the ratio of the diameters of the counterweight disk and increases if as many radial counterweights as possible with a length of 0.25λ are fixed around the disk circumference, ensuring their reliable contact with the counterweight disk.

The DDRR antenna considered here (Fig. 38) uses two identical rings (hence the name "two-ring-circular"). At the bottom, instead of a metal surface, a closed ring is used with the same dimensions as the top. All grounding points are connected to it according to the classical scheme. Despite a slight decrease in the efficiency of the antenna, this design is very attractive for placing it on the balcony, in addition, with such a solution, it is of interest to connoisseurs of the 40-meter range. Using square constructs instead of rings, the antenna on the balcony resembles a clothes dryer and does not cause unnecessary questions from neighbors.

All its sizes and capacitor ratings are presented in Table 4. In a budget option, an expensive vacuum capacitor can be replaced with feeder sections in a range, and fine tuning is done with a 1-15pF trimmer with an air dielectric, remembering that the linear capacity of the RG213 cable = (97pF / m).

Table 4.

Amateur bands, (m)
Frame perimeter (m)

Practical experience of using the DDRR double ring antenna was described by DJ2RE. The tested antenna of the 10-meter range was made of a copper tube with an outer diameter of 7 mm. To fine tune the antenna, two 60x60 mm copper swivel plates were used between the upper "hot" end of the conductor and the lower ring.

The comparison antenna was a rotary three-element Yagi located 12 m from the ground. The DDRR antenna was located at a height of 9 m. Its lower ring was grounded only through the shield of the coaxial cable. During the test reception, the quality of the DDRR antenna immediately manifested itself as a circular radiator. According to the author of the tests, the received signal was two points lower on the S-meter of the Yagi signal with a gain of about 8 dB. When transmitting with a power of up to 150 W, 125 communication sessions were performed.

Note: According to the author of the tests, it turns out that the DDRR antenna at the time of testing had a gain of about 6 dB. This phenomenon is often misleading because of the proximity of different antennas of the same range, and the properties of EME re-emission by them loses the purity of the experiment.

5. Capacitive antennas.

Before starting this topic, I want to remember the story. In the 60s of the 19th century, while formulating a system of equations for describing electromagnetic phenomena, J.C. Maxwell was faced with the fact that the equation for the direct current magnetic field and the conservation equation electric charges variable fields (equation of continuity) are incompatible. To eliminate the contradiction, Maxwell, having no experimental data for that, postulated that the magnetic field is generated not only by the movement of charges, but also by a change in the electric field, just as an electric field is generated not only by charges, but also by a change in the magnetic field. The quantity where is the electric induction, which he added to the conduction current density, Maxwell called bias current... Electromagnetic induction has a magnetoelectric analogue, and the field equations have acquired remarkable symmetry. So, one of the most fundamental laws of nature was speculatively discovered, the consequence of which is the existence of electromagnetic waves. Subsequently, G. Hertz, relying on this theory, proved that the electromagnetic field emitted by an electric vibrator is equal to the field emitted by a capacitive emitter!

If so, let us make sure once again what happens when a closed oscillatory circuit turns into an open one and how can the electric field E be detected? To do this, next to the oscillating circuit, we place an electric field indicator, this is a vibrator, in the gap of which an incandescent lamp is included, it is not yet lit, see Fig. 39.a. Gradually we open the circuit, and we observe that the lamp of the indicator of the electric field lights up, Fig. 39.b. The electric field is no longer concentrated between the plates of the capacitor, its lines of force go from one plate to another through the open space. Thus, we have experimental confirmation of JK Maxwell's assertion that a capacitive emitter generates an electromagnetic wave. In this experiment, a strong high-frequency electric field is formed around the plates, the change of which over time induces eddy displacement currents in the surrounding space (Eichenwald A.A. forming a high-frequency electromagnetic field!

Nikola Tesla drew attention to this fact that with the help of very small emitters in the HF range, it is possible to create a sufficiently effective device for emitting an electromagnetic wave. This is how Tesla's resonant transformer was born.

* The design of the EH antenna by T. Hard and the transformer (dipole) by N. Tesla.

Is it worth, once again, to assert that the EH antenna designed by T. Hard (W5QJR), see Fig. 40, is a copy of the original Tesla antenna, see Fig.1. Antennas differ only in size, where Nikola Tesla used frequencies in kilohertz, and T. Hard created a design for operation in the HF range.

The same resonant circuit, the same capacitive radiator with an inductor and a coupling coil. The Ted Hard antenna is the closest analogue of the Nikola Tesla antenna and was patented as, "Coaxial inductor and dipole EH antenna" (US patent US 6956535 B2 dated 18.10.2005) for operation in the HF range.

Ted Hard's HF capacitive antenna is inductively coupled to the feeder, although a number of capacitive antennas with capacitive, direct and transformer coupled have long existed.

The base of the supporting structure of the engineer and radio amateur T. Hard is an inexpensive plastic pipe with good insulating characteristics. Foil in the form of cylinders fits tightly around it, thereby forming antenna radiators with a small capacity. The inductance L1 of the formed serial oscillatory circuit is located behind the emitter aperture. The L2 inductor located in the center of the radiator compensates for the antiphase radiation of the L1 coil. The antenna power connector (from the generator) W1 is located at the bottom, it is convenient for connecting the power feeder going down.

In this design, the antenna is tuned by two elements, L1 and L3. By selecting the turns of the L1 coil, the antenna is tuned to the sequential resonance mode for maximum radiation, where the antenna acquires a capacitive character. The tap from the inductor determines the input impedance of the antenna and whether the radio amateur has a 50 or 75 Ohm feeder. By selecting a tap from the L1 coil, you can achieve VSWR = 1.1-1.2. With the inductor L3, compensation is achieved with a capacitive nature, and the antenna takes on an active character, in terms of input impedance close to VSWR = 1.0-1.1.

Note: Coils L1 and L2 are wound in opposite directions, and coils L1 and L3 are perpendicular to each other to reduce mutual influence.

This antenna design undoubtedly deserves the attention of radio amateurs who have at their disposal only a balcony or loggia.

Meanwhile, developments do not stand in one place and radio amateurs, having appreciated the invention of N. Tesla and the design of Ted Hart, began to offer other options for capacitive antennas.

* Antenna family "Isotron" is a simple example of flat curved capacitive radiators, it is manufactured by the industry for use by its radio amateurs, see Fig. 42. The "Isotron" antenna has no fundamental difference with the T. Horda antenna. All the same serial oscillatory circuit, all the same capacitive emitters.

Namely, the element of radiation here is a radiating capacity (Sizl.) In the form of two plates bent at an angle of about 90-100 degrees, the resonance is adjusted by decreasing or increasing the bending angle, i.e. their capacity. According to one version, communication with the antenna is carried out by direct connection of the feeder and the serial oscillatory circuit, in this case the SWR determines the L / C ratio of the formed circuit. According to another version, which radio amateurs began to use, communication is carried out according to the classical scheme, through the communication coil Lsv. VSWR in this case is adjusted by changing the coupling between the serial resonance coil L1 and the coupling coil Lsv. The antenna is efficient and to some extent effective, but it has a major drawback, the inductance coil, when placed in the factory version, is located in the center of the capacitive radiator, works in antiphase with it, which reduces the antenna efficiency by about 5-8-dB. It is enough to turn the plane of this coil by 90 degrees and the antenna efficiency will increase significantly.

Optimal antenna sizes are summarized in Table 5.

* Multi-band option.

All Isotron antennas are single-band, which causes a number of inconveniences when changing from band to band and placing them. When two (three, four) such antennas are connected in parallel, mounted on a common bus, operating at frequencies f1; f2 and fn, their interaction is excluded due to the high resistance of the serial oscillatory circuit of the antenna, which does not participate in resonance. When two single-resonant antennas connected in parallel are manufactured on a common bus, the efficiency (efficiency) and bandwidth of such an antenna will be higher. Using the last version of the in-phase connection of two single-band antennas, it must be remembered that the total input impedance of the antennas will be half as much and it is necessary to take appropriate measures by referring to (Table 1). Antenna modification on a common substrate is shown in Fig. 42 (bottom). Needless to say, a choke choke line is an integral part of any mini antenna.

Studying the simplest "Isotron", we came to the conclusion that the gain of this antenna is insufficient due to the placement of a resonant inductor between the radiating plates. As a result, this design was improved by radio amateurs in France, and the inductor was moved outside the working environment of the capacitive radiator, see Fig. 43. The antenna circuit is directly connected to the feeder, which simplifies the design, but still complicates full coordination with it.

As can be seen from the presented figures and photos, this antenna is quite simple in design, especially in tuning it to resonance, where it is enough to slightly change the distance between the radiators. If the plates are reversed, the upper one is made "hot" and the lower one is connected to the feeder braid, a common bus for a number of other antennas of the same type can be made, then you can get a multi-band antenna system, or a number of identical antennas connected in phase, capable of increasing the overall gain.

Radio amateur with radio call sign F1RFM, kindly provided for general review his antenna design with calculations for 4 radio amateur bands, the diagram of which is shown in Fig. 44.

* Antenna "Biplane"

The Biplane antenna is named for its resemblance to the placement of the twin wings of aircraft of the early 20th century by the Biplane design, and its invention belongs to a group of radio amateurs (Fig. 45). Antenna "Biplane" consists of two sequential oscillatory circuits L1; C1 and L2; C2, connected in anti-parallel. Emitter power supply, symmetrical with direct coupling. The planes of capacitors C1 and C2 are used as radiating elements. Each emitter is made of two duralumin plates and is located on both sides of the inductance coils.

To eliminate mutual influence, inductors are wound oppositely or are located perpendicular to each other. According to the authors, the area of ​​each plate will be 64.5 cm for the range of 20 meters, 129 cm for 40 meters, 258 cm for 80 meters, and 516 cm for the 160 meter range, respectively.

The adjustment is carried out in two stages and can be carried out by elements C1 and C2 by changing the distance between the plates. The minimum VSWR is achieved by changing the capacitances C1 and C2 by tuning the transmitter to the frequency. The antenna is very difficult to set up and requires a complex construction of sealing against the influence of external precipitation. It has no development prospects and is unprofitable.

On the topic of capacitive antennas, it is worth noting that they have occupied a special niche among radio amateurs who do not have the opportunity to install full-fledged antennas, which only have a balcony or loggia at their disposal. Radio amateurs, who have the opportunity to install a low mast on a small antenna field, also use such antennas. All shortened antennas are collectively referred to as QRP antennas. In addition, radio amateurs have a number of errors in the installation and operation of shortened antennas, this is the absence of a locking "feeder choke" or a very close location of the latter on a ferrite base to the shortened antenna canvas. In the first case, the antenna feeder begins to radiate, and in the second, the ferrite of such a choke is a "black hole" and reduces its efficiency.

* EH-antenna of the troops of the SA of the USSR in the 40s - 50s of the last century.

The antenna was welded from duralumin pipes with a diameter of 10 and 20 mm. A flat, broadband symmetric split dipole about 2 meters long and 0.75 meters wide. Operating frequency range 2-12MHz. Why not a balcony antenna? It was mounted on the roof of a mobile radio room in a horizontal position at a height of about 1m.

The author of this article, back in the 90s, reproduced this design on the balcony of the second floor, and the emitters were made under a clothes dryer on wooden blocks outside the balcony. Copper insulated wires were stretched instead of ropes, see Fig. 46.a. The antenna was tuned using an oscillatory circuit L1C1, a capacitor C2 for coupling with the antenna and a coupling coil Lw. with transceiver, see Fig. 46.b. All air-insulated capacitors with a capacity of 2 * 12-495pF were used from tube radios of the 60s.

Inductor L1 diameter 50 mm; 20 turns; wire 1.2 mm; pitch 3.5 mm. On top of this coil, a plastic pipe (50mm) sawn along the length was tightly put on. A communication coil Lsv was wound on top of it. - 5 turns with taps from 3; 4 and 5 turns, wire 2.2 mm. For all capacitors, only stator contacts were used, and the axes (rotors) on capacitors C2 and C3 were connected by an insulating bridge for synchronization of rotation. A two-wire line should be no more than 2.0-2.5 meters, this is just the distance from the antenna (dryer) to the matching device on the windowsill. The antenna was built in the range of 1.8-14.5 MHz, but when the resonant circuit was changed to other parameters, such an antenna could work up to 30 MHz. In the original, in series with the transmission line in such a design, current indicators were provided, which were adjusted according to the maximum readings, but in a simplified version between the two wires of the two-wire line, a fluorescent lamp hung perpendicular to it, which, at the minimum output power, shone only in the middle, and at maximum power ( at resonance) the glow reached the edges of the lamp. The coordination with the radio station was carried out with the P1 switch and was monitored by the SWR meter. The bandwidth of such an antenna was more than sufficient to operate on each of the amateur bands. With a power input of 40-50W. The antenna did not interfere with television to the neighbors. Other things now, when everyone has switched to digital and cable television, you can supply up to 100W.

This type of antenna refers to capacitive and differs from EH antennas only in the circuit for switching on the emitters. It differs in their shape and size, but at the same time, it has the ability to rebuild in the HF range and be used for its intended purpose - drying clothes ...

* Combination of E-emitter and H-emitter.

Using a capacitive emitter outside the balcony (loggia), this construct can be combined with a magnetic antenna, as Alexander Grachev did ( UA6AGW), combining the magnetic frame with a half-wave shortened dipole. In the radio amateur world, it is well known and practiced by the author at his summer cottage. The electrical circuit of the antenna is quite simple and is shown in Fig. 47.

Capacitor C1 is a trimmer within the range, and the required range can be set by connecting an additional capacitor to the contacts K1. The matching of the antenna and the feeder is subject to the same laws, i.e. loop at the point of zero voltage, see Fig. 30. Fig. 31. Such a modification has the advantage that its installation can be made really invisible to prying eyes and, moreover, it will work quite effectively in two or three amateur frequency ranges.

A shortened spiral-shaped dipole on a plastic base fits perfectly inside the loggia with wooden frames, but the owner of this antenna did not dare to expose it outside the loggia. I do not think that the owner of this apartment is delighted with this beauty.

Balcony antenna - 14/21/28 MHz dipole fits well outside the balcony. It is inconspicuous and does not draw attention to itself. You can build such an antenna by following the link

Afterword:

In conclusion of the material on HF balcony antennas, I would like to say to those who do not have and do not expect access to the roof of their house - it is better to have a bad antenna than none at all. Everyone can work with a three-element Uda-Yagi antenna or a double square, but choose the best option, to develop and build a balcony antenna, to work on the air at the same level, is not given to everyone. Do not change your hobby, it will always come in handy for resting your soul and training your brain, during your vacation or in retirement. Communication on the air gives much more benefit than communication on the Internet. Men who do not have a hobby of their own, have no purpose in life, live less.

73! Sushko S.A. (ex. UA9LBG)