I decided to study more deeply the issue of how a discone antenna works in order to understand whether it really is the choice I need. And you know, this is a really interesting antenna that can be developed to obtain good potential. Perhaps I will follow the path of those who design complex-type antennas. But I will install such a complex antenna at the dacha; in the city, an antenna with fewer requirements will suit me.

So, what are the characteristics of the antenna that interest me:

• Circular radiation pattern,
• broadband,
• wind resistance,
• low material consumption.

Earlier I wrote that I had a choice between a log-periodic and a disk-cone antenna. I thought about my decision and came to the conclusion that for my specific tasks of monitoring radio broadcasts, a discone antenna is more suitable. And due to the specific location of the dacha plot, at the dacha it will be more convenient for me to monitor NOAA satellites and long-distance passes in the CB and ten-meter range.

So, what is a discone antenna? As the name suggests, a disc-cone antenna consists of a disk (radiating element) and a cone (counterweight to the radiating element). I’ll start the analysis of this antenna with this classic version.

This intricate shape of the antenna leads to the misconception that a discone antenna has horizontal polarization. In fact, the polarization of this antenna is vertical. The antenna is an infinite number of V-shaped antennas inclined towards the horizon (the active element is up and the counterweight is down). If part of the disk were one arm of the antenna and the other the other, then the polarization would be horizontal. In our case, one shoulder is tilted horizontally, and the other at an angle from the horizon to the ground. The result is a donut-shaped radiation pattern.

Disc and cone are good, but this design produces wild windage. Therefore, in commercial developments, the disk and cone are replaced with a wire structure. This approach makes it possible to reduce the wind load, reduce the cost of the manufacturing process, reduce the material consumption of antenna manufacturing and simplify its assembly. And this is exactly the path I will follow when making my antenna.

By manipulating the materials and structures of the disk and cone, masses of various disk-cone antennas are created. One of the most common discone antennas is the railway antenna. As an example, consider the antenna from VIAM-RADIO. This antenna is designed to work with locomotive radio stations in the ranges 151-156 MHz and 307-344 MHz. Because of high speeds and the requirements for strength characteristics, the antenna was made in the form of a welded structure with additional elements reinforcing the structure.

Locomotive antenna AL/23 disc-cone

There are alternative approaches to increase bandwidth. In the ranges from hundreds to thousands of megahertz, the dimensions of disc-cone antennas remain acceptable, but as the frequency decreases, the dimensions become inconvenient both for installation and for design calculations. But there is Alternative option increasing the bandwidth to approximately 25 MHz. To do this, an additional pin is connected to the disk (or the conductors replacing it), thereby increasing the bandwidth. But if you just connect the pin, its influence will worsen the parameters and it should only work on “its own range”. To do this, the pin is cut off from the disk using inductance.

But this option immediately turns the antenna into a large one, and in addition, transmission cannot be carried out in the additional range. An additional piece of range is added only for reception. Actually, such an antenna is ideal for scanners.

As soon as I calculate the dimensions I need, I will publish them. Then I will start collecting materials to build this antenna.

Greetings to fellow hobbyists! Here's my setup:

To connect the receiver to the antenna, I decided to use a good satellite cable RG-6 Reeme. There were several reasons for this:

1. Low rated losses at 1000 MHz (About 17 dB at 100 m - one of the best indicators among coaxials)
2. Cheapness of connectors (besides, they were available at home)
3. I already had a cable laid on the roof to satellite dish, it is currently no longer in use

The difference in wave impedances was not particularly concerning; the loss of 4% of the signal power due to mismatch is nothing compared to the possible losses from using a 50-ohm cable with higher losses.

When faced with the choice of antenna for my receiver, I settled on three candidates: 6-element, Super and discocone. All antennas were pre-rated for 75 ohms and were quite precisely manufactured. I tested Franklin, Super-J and discocone in turn. Oddly enough, the discone antenna won.

I tried to configure Franklin by shifting the connection points on the quarter-wave cable, but the results were still not impressive. It's the same story with Super-J. Discone worked better. Here are my guesses about this:

1. Franklin is a symmetrical antenna; if you simply connect an asymmetrical power line (coaxial cable) to it, this will distort its directional pattern, which will naturally lead to a decrease in gain. Ideally, you need to additionally use a balancing device.
2. Theoretical calculation is good, but in practice the necessary coordination may not be achieved due to the influence of many factors that cannot be taken into account in the calculation
3. Precision manufacturing. If you make an antenna with millimeter precision, then perhaps it will work normally.

Here's what I liked about the disco cone:

1. Compact size. Height about 80 mm, width about 70 mm
2. Broadband. The antenna does not require adjustment and starts working immediately after assembly.
3. Ease of manufacture. The disc cone is not critical to manufacturing accuracy. You can safely make a mistake of +/- 5 mm in size (tested by practice). Of course, there is no need to make mistakes in centimeters.

Drawing with dimensions:

The thick dot in the center of the disk indicates the place where the central pin of the F-connector is soldered to the disk. The disk and base are made of one-sided foil PCB. The cone's components are made of copper wire with a diameter of 2 millimeters. Copper is tinned, but this is not necessary. Here's what happened:

During the experiments, it turned out that even a slight increase in cable length leads to a deterioration in reception. Because The antenna must be installed on the roof and connected by a 40-meter cable; an amplifier is not necessary. I bought a regular satellite amplifier OPENMAX A04-20 at 20 dB for 150 rubles. It was also necessary to make sure that the receiver input was short-circuited DC. As a result, this scheme was born:

For the injector: The fuse protects the power supply from possible short circuits (for example, if the cable breaks). Protective diode D1 protects the circuit from lightning overvoltages (seen in the circuit satellite tuner). When the voltage is above 24 V, it breaks through and short-circuits the circuit. Capacitor C2 is anti-interference. Choke L1 - RF filter, wound on a toroidal ferrite core (10 turns of PEL 1.0 wire)

To short-circuit the receiver's DC input, I used a quarter-wave short-circuited loop from a piece of coaxial cable. The scheme has proven itself to be excellent. During testing, the loop did not affect the reception quality at all. The length of the coaxial cable segment was 45 mm (taking into account the shortening factor and the length of the F-socket in the splitter).

The receiver was placed in another case and covered with a transparent plexi cover. It’s more beautiful and the LEDs are clearly visible. General form designs:

Happy radarspotting!

The cone is made in the form of a horn from a sheet of copper or some other material that is easy to solder. The power cable is run inside the cone and its outer braid is soldered to the cone, and a cleaned section of the inner core 100 mm long is soldered to a metal disk. The disk is held in a horizontal position using insulating supports.

To establish long-distance radio communications in the ranges of 144-146 MHz and especially at 420-425 MHz, it is necessary to concentrate the radiation of electromagnetic energy in the form of a narrow beam and direct it as close as possible to the horizon. At the same time, it is also necessary to be able to establish radio communications with correspondents located in different directions from the radio station with a fixed antenna. For this case, the antenna must have a radiation pattern in the vertical plane in the form of an elongated figure eight, and in the horizontal plane - in the form of a circle. A similar diagram can be obtained by designing a biconical antenna (Fig. 2), which consists of two metal cones, one of which is connected to the middle core of the cable, and to the other its braid. The disadvantage of such an antenna is the need for symmetrical excitation.

A broadband biconical disc-cone antenna (Fig. 3), in which the disk plays the role of the upper cone, does not require symmetrical excitation. Table 1 shows the dimensions of disc-cone antennas designed for operation in the amateur bands.

Table 1
	Dimensions, mm
Operating range
frequency MHz

With the selected antenna dimensions, it is advisable to carry out work in the region of the lowest operating frequencies, since as the operating frequency increases, the angle between the direction of maximum radiation and the horizon increases. The antenna is powered by a cable with a characteristic impedance of about 60-70 ohms without matching devices. The disk is isolated from the cone, which can be grounded. To operate in the range of 38-40 MHz, the cone and disk are made of pins with a diameter of 3 - 5 mm (Fig. 4). The maximum distance between pins should not exceed 0.05L.

Literature:

1. K. Rothhammel. Antennas. Moscow "Energy". 1979
2. F. Burdeyny and others. Shortwave Directory. From DOSAAF, Moscow. 1959

Compared to the coaxial antenna, the disc-cone antenna, while also having pie chart directionality and the same method of power supply, has a significantly larger bandwidth. Compared to a conventional dipole, the gain of this antenna is -3dB. This reduction in gain should not be surprising since the disc-cone antenna has a correct radiation pattern over a very large bandwidth. The design of the disc-cone antenna shown in Fig. 11-40, subject to the specified dimensions and direct power supply via a coaxial cable with a characteristic impedance of 60 Ohms, has a passband from 85 to 500 MHz.

Fig.1

The cone is made in the form of a horn from a sheet of copper or some other material that is easy to solder. The power cable is run inside the cone and its outer braid is soldered to the cone, and a cleaned section of the inner core 100 mm long is soldered to a metal disk. The disk is held in a horizontal position using insulating supports.

To establish long-distance radio communications in the ranges of 144-146 MHz and especially at 420-425 MHz, it is necessary to concentrate the radiation of electromagnetic energy in the form of a narrow beam and direct it as close as possible to the horizon. At the same time, it is also necessary to be able to establish radio communications with correspondents located in different directions from the radio station with a fixed antenna. For this case, the antenna must have a radiation pattern in the vertical plane in the form of an elongated figure eight, and in the horizontal plane - in the form of a circle. A similar diagram can be obtained by designing a biconical antenna (Fig. 2), which consists of two metal cones, one of which is connected to the middle core of the cable, and to the other its braid. The disadvantage of such an antenna is the need for symmetrical excitation.

Fig.2

A broadband biconical disc-cone antenna (Fig. 3), in which the disk plays the role of the upper cone, does not require symmetrical excitation. Table 1 shows the dimensions of disc-cone antennas designed for operation in the amateur bands.

Table 1
	Dimensions, mm
Operating range
frequency MHz

With the selected antenna dimensions, it is advisable to carry out work in the region of the lowest operating frequencies, since as the operating frequency increases, the angle between the direction of maximum radiation and the horizon increases. The antenna is powered by a cable with a characteristic impedance of about 60-70 ohms without matching devices. The disk is isolated from the cone, which can be grounded. To operate in the range of 38-40 MHz, the cone and disk are made of pins with a diameter of 3 - 5 mm (Fig. 4). The maximum distance between pins should not exceed 0.05L.

A disk-cone antenna is a characteristic emitter, which gives its name to the first part of the complex name of the product, equipped with a “ground” made of metal reinforcement or simply a cone. In the partial range, the design will allow linear vertical polarization to be obtained as the wave moves between the disk and the cone. This is what is needed for radio communication. In addition, we will consider a modification that turns the device into a circularly polarized emitter in the direction perpendicular to the disk and opposite to the location of the earth. Readers will learn how to assemble a discone antenna themselves.

Disc-cone antennas

Important! Omnidirectional discone antennas are often used in the HF band. They do not differ in obvious amplification for the stated reason.

The topic of today's conversation is a do-it-yourself discone antenna. Rumor has it that the first patent, number 2368663 (USA), was taken by A.G. Kandoian. The advantage of the device is its wide range of operating frequencies. Of course, the gain is inferior to the dipole. On the range it is usually possible to connect to the cable without coordination, plus the design itself is not critical to dimensional accuracy. In the decimeter range you have to take a solid cone; on HF and meter waves, most people need a skeletal shape. The disk degenerates into a set of conductor-rays with a single center. This reduces the wind load; at long waves, the dimensions of the cone and disk acquire gigantic values. 6, 8 or 12 rods.

Attention! The disk and cone are powered in antiphase.

The central core of the cable is connected to a disk of a certain size. The role of the earth is played by a bundle of metal reinforcement, if there is no desire to make a cone with your own hands. It is clear that the radiation pattern is distorted. Unevenness occurs in the azimuthal direction. And the radiation pattern of a typical disk-cone antenna resembles a torus (donut). The wave arises between the disk and the cone. Range depends on distance. For example, we present the design indicated on the website http://elektronika.rukodelkino.com/stati/antenni/35-disko-konusnaya-antenna.html.

The meaning of the work has already been described, implementation for frequencies 85 - 500 MHz:

The characteristic impedance of the device is 60 Ohms, get ready to match it in any convenient way. The central core is connected to the middle of the disk from below, the cone is combined with the screen. Thus, it turns out something like an open waveguide, where the wave propagates and is radiated. The gain is minus 3 dB compared to a half-wave dipole. Online calculators There is no calculation, we will find a suitable method. Let's analyze our own design. We believe that the minimum and maximum distances between the disk and the cone should correlate with the boundary wavelengths of the range. First, let's calculate the dimensions:

λmin = 299,792,458 / 500,000,000 = 60 cm.

λmax = 299,792,458 / 85,000,000 = 3.53 m.

We rely on the obtained values. Let's divide both by four and see what's left. We have: 15 and 88.2 cm. We see that the sizes are not tied to anything. According to the pictures and formulas:

The last two parameters determine the upper limit frequency of the antenna, as Neil writes, the results of whose work we have now used, a discone antenna behaves like a high-pass filter. There is a certain limiting lower frequency, by which the side of the cone is calculated, where the SWR is 3. When going through the limit down, the SWR begins to grow rapidly, which makes the use of the device impractical. Within operating limits, the parameter gradually decreases to 1.5. Take the length of the side of the cone a little more than a quarter maximum length waves. Let us add that the diameter of the disk does not depend on the apex angle, which can differ from 60 degrees.

Let's compare the numbers with those indicated above: from the calculations it is clear that the side wall is taken equal (!) to the minimum wavelength, which does not correspond to the book. To be sure, we examine the table from the literature for similarities in order to finally confirm or dispel doubts (the site owners calculated using the wrong parameter).

It can be seen that the antenna dimensions decrease linearly with increasing frequency. For example, at 14 MHz it is almost twice as much as at 28 MHz. Therefore, for 85 MHz we will find the necessary parameters by proportion (recall that the vertex angle in the information given earlier is 60 degrees). 85 divided by 14 = 6. Therefore, we divide the dimensions by the resulting coefficient, it turns out:

1. The apex angle is 60 degrees.
2. Base diameter and side length – 91 cm.
3. Disc diameter – 61 cm.
4. The gap between the disk and the cone is 4 cm.

The upper frequency is not necessarily 500 MHz; they said that the figure depends on the cross-sectional diameter of the cone. The smaller the hole for the cable, the higher the frequencies the antenna operates with. So, they showed that you cannot trust calculations from the network with 100% probability. It is possible that some design innovations with unknown data were used there, but, more likely, the authors cut the cone down to the size of a disk. Therefore, it will not work at lower frequencies.

We can guess how the maximum operating frequency is calculated: a quarter of the wavelength is equal to the distance from the point where the core is attached to the disk to the cut of the cone. Just by analogy. Check the fact without the VashTechnik portal, we consider the thesis obvious.

Disc-cone antenna shape

Attentive readers will have noticed that not all reviews have a 60-degree apex angle. Why this parameter was chosen by theorists and experienced practitioners. Studies were carried out for a 50 Ohm cable, which clearly showed that this apex angle gives the widest range, where the SWR does not exceed 2. In other cases, in the direction of increase and decrease, various peaks and narrowings of the band were observed. It turns out that the angle of 60 degrees at the apex is theoretically justified. If the lower limit is not important, increase by 10 degrees. The SWR becomes more acceptable without changing the lower boundary area.

As for skeletal forms instead of solid cones and disks, this significantly reduces the weight of the product and reduces the wind load. Imagine huge products made of steel, especially copper! The weight is considerable.

So, it is shown that a broadband discone antenna exhibits a gain less than that of a vibrator. At the same time, the design is not so sensitive to dimensional deviations and is relatively complex. In other words, making a discone antenna yourself is possible, but difficult. Let's summarize:

• The key is the size of the side of the cone, which determines the calculation of other dimensions.
• We take the apex angle to be 60 degrees for radio communications and WiFi.

They promised to show how to improve the discone antenna. Please! The disk is powered not from the cable directly, but through a piece of wire, which constitutes a line segment with infinitely high resistance when passing through a certain cutoff frequency. A hole is cut in the center of the disk through which the core supplies additional disk, located above, radiating to the zenith. This design catches almost any linear polarization emanating from a vertical point. The need is unknown to the authors. The example is taken from the literature.

The peculiarity of discone antennas is that it is possible to make a giant structure that receives at all frequencies. The main thing is to correctly execute the vertex responsible for the upper range. Of course, as you approach the microwave, the requirements for surface roughness increase; light rays, for example, are reflected from a mirror. In this light, it is understandable why such interest is shown in the products. A half-wave vibrator provides good amplification, but the device will not provide such a luxurious band. A decent-sized homemade disc-cone antenna catches almost everything! From all directions. We recommend making a discone antenna and equipping the structure with a good input filter.