Radio frequencies. VHF and UHF bands What can be heard on 144 MHz

A short time ago, home-made equipment was mainly used to work on the 144-145 MHz band. VHF transverters were popular among radio amateurs, many of which were comparable in size to the transceiver itself used with it. Radio amateurs converted decommissioned industrial VHF radio stations of the Palma type to the amateur VHF band of 145 MHz, receiving a radio station operating on several channels. Then the Violas became available to radio amateurs, and later the Mayaks, operating on forty channels. These radios then looked fantastic in their capabilities!

At present, it is relatively inexpensive to purchase multi-channel portable VHF transceivers of world famous companies - YAESU, KENWOOD, ALINCO, which, in terms of their parameters and ease of use, are significantly superior to both home-made equipment in the 145 MHz band and converted industrial equipment - Palma ”, “Lighthouses”, “Violas”.

But to work through a repeater from home, office, while driving when working from a car, you need an antenna that is more effective than the “rubber band” used in conjunction with a portable radio station. When using a stationary "proprietary" VHF station, it is often advisable to use a home-made VHF antenna with it, since a decent "proprietary" outdoor antenna in the 145 MHz range is not cheap.

This material is devoted to the manufacture of simple home-made antennas suitable for use with stationary and portable VHF radio stations.

Features of 145 MHz Antennas

Due to the fact that for the manufacture of antennas in the 145 MHz band, thick wire is usually used - with a diameter of 1 to 10 mm (sometimes thicker vibrators are used, especially in commercial antennas), then 145 MHz band antennas are broadband. This often makes it possible, when making the antenna exactly according to the specified dimensions, to do without its additional tuning to the 145 MHz band.

To tune antennas in the 145 MHz range, you must have an SWR meter. It can be both a home-made device and industrial production. On the 145 MHz band, radio amateurs practically do not use bridge antenna impedance meters, due to the apparent complexity of their correct manufacture. Although, with careful manufacture of the bridge meter and, therefore, its correct operation in this range, it is possible to accurately determine the input impedance of VHF antennas. But even using only an SWR - a pass-through type meter, it is quite possible to tune home-made VHF antennas. The power of 0.5 W, which is provided by imported portable radio stations in the “LOW” mode and domestic portable radio stations of the VHF range such as “Dnepr”, “Viola”, “VEBR”, is quite enough to operate many types of SWR meters. The "LOW" mode allows you to tune the antennas without fear of failure of the output stage of the radio station with any input impedance of the antenna.

Before starting to tune the VHF antenna, it is advisable to make sure that the SWR meter readings are correct. It's a good idea to have two SWR meters rated for 50 and 75 ohm transmission paths. When setting up VHF antennas, it is desirable to have a control antenna, which can be either an "elastic band" from a portable radio station or a home-made quarter-wave pin. When tuning the antenna, the level of field strength created by the tuned antenna relative to the control one is measured. This makes it possible to judge the comparative efficiency of the tuned antenna. Of course, if a standard calibrated field strength meter is used in the measurements, an accurate estimate of the antenna's performance can be obtained. When using a calibrated field meter, it is easy to take the antenna pattern as well. But even using home-made field strength meters for measurements and having received only a qualitative picture of the distribution of the electromagnetic field strength, it is possible to fully conclude about the efficiency of the tuned antenna and approximately estimate its radiation pattern. Consider the practical design of VHF antennas.

Simple Antennas

The simplest outdoor VHF antenna (Fig. 1) can be made using an antenna that works in conjunction with a portable radio station. A metal corner is attached to the window frame from the outside (Fig. 2) or from the inside on an extension wooden bar, in the center of which there is a socket for connecting this antenna. It is necessary to strive to ensure that the coaxial cable leading to the antenna is the minimum required length. 4 counterweights 50 cm long are attached along the edges of the corner. It is necessary to ensure good electrical contact of the counterweights, the antenna connector with the metal corner. The shortened twisted antenna of the radio station has an input impedance in the range of 30-40 ohms, so a coaxial cable with a characteristic impedance of 50 ohms can be used to power it. With the help of the tilt angle of the counterweights, it is possible to change the input impedance of the antenna within certain limits, and, therefore, to match the antenna with the coaxial cable. Instead of the branded "elastic band", you can temporarily use an antenna made of copper wire with a diameter of 1-2 mm and a length of 48 cm, which is inserted into the antenna socket with its sharply sharpened end.

Figure 1. A simple outdoor VHF antenna

Figure 2. Construction of a simple outdoor VHF antenna

The VHF antenna, made of a coaxial cable with the outer braid removed, works reliably. The cable is terminated in the RF connector similar to the connector of the "proprietary" antenna (Fig. 3). The length of the coaxial cable used to make the antenna is 48 cm. Such an antenna can be used in conjunction with a portable radio station to replace a broken or lost standard antenna.

Figure 3. A simple homemade VHF antenna

For quick production of a remote VHF antenna, you can use a connecting coaxial cable 2-3 meters long, which is terminated with connectors corresponding to the antenna jack of the radio station and antenna. The antenna can be connected to such a piece of cable using a high-frequency tee (Fig. 4). In this case, an “elastic band” antenna is connected from one end of the tee, and counterweights 50 cm long are wound from the other end of the tee, or another type of radio technical “ground” for the VHF antenna is connected through the connector.

Figure 4. A simple remote VHF antenna

Homemade portable radio antennas

If the standard antenna of the portable radio station is lost or broken, you can make a home-made twisted VHF antenna. For this, a base is used - polyethylene insulation of a coaxial cable with a diameter of 7-12 mm and a length of 10-15 cm, on which 50 cm of copper wire with a diameter of 1-1.5 mm is initially wound. To tune a twisted antenna, it is very convenient to use a frequency response meter, but you can also use an ordinary SWR meter. Initially, the resonant frequency of the assembled antenna is determined, then, biting off part of the turns, shifting, pushing the turns of the antenna, tune the twisted antenna to resonance at 145 MHz.

This procedure is not very complicated, and by setting up 2-3 twisted antennas, a radio amateur can tune new twisted antennas in just 5-10 minutes, of course, with the above devices. After tuning the antenna, it is necessary to fix the turns either with electrical tape, or with cambric soaked in acetone, or with a heat shrink tube. After fixing the turns, it is necessary to once again check the frequency of the antenna and, if necessary, adjust it with the help of the upper turns.

It should be noted that in the "proprietary" shortened twisted antennas, heat-shrinkable tubes are used to fix the antenna conductor.

Half wave field antenna

For efficient operation of quarter-wave antennas, it is necessary to use several quarter-wave counterbalances. This complicates the design for a field quarter-wave antenna, which must be placed in space relative to the VHF transceiver. In this case, you can use a VHF antenna with an electrical length L / 2, which does not require counterweights for its operation, and provides a radiation pattern pressed to the ground and ease of installation. For an antenna with an electrical length L/2, there is a problem of matching its high input impedance with the low wave impedance of the coaxial cable. An antenna with a length of L/2 and a diameter of 1 mm will have an input impedance on the 145 MHz band of about 1000 ohms. Matching with a quarter-wave resonator, which is optimal in this case, is not always convenient in practice, since it requires the selection of points for connecting the coaxial cable to the resonator for its efficient operation and fine tuning of the antenna pin to resonance. The dimensions of the resonator for the 145 MHz band are also relatively large. Destabilizing factors on the antenna, when it is matched with a resonator, will manifest themselves especially strongly.

However, at low powers supplied to the antenna, quite satisfactory matching can be achieved using a P-loop, similarly as described in the literature. A diagram of a half-wave antenna and its matching device is shown in fig. 5. The length of the antenna pin is chosen to be slightly shorter or longer than the L/2 length. This is necessary because even with a small difference in the electrical length of the antenna from L / 2, the active resistance of the antenna impedance noticeably decreases, and its reactive part at the initial stage increases slightly. As a result, it is possible to match such a shortened antenna using the P-loop with greater efficiency than the matching of an antenna with a length of exactly L / 2. It is preferable to use an antenna slightly longer than L/2.

Figure 5. VHF antenna matching using a P-loop

In the matching device, air tuning capacitors of the KPVM-1 type were used. Coil L1 contains 5 turns of silver-plated wire with a diameter of 1 mm, wound on a mandrel with a diameter of 6 mm and a pitch of 2 mm.

Antenna tuning is not difficult. By including an SWR meter in the antenna cable path and at the same time measuring the level of the field strength created by the antenna, by changing the capacitance of the variable capacitors C1 and C2, compressing and stretching the turns of the L1 coil, the minimum readings of the SWR meter and, accordingly, the maximum readings of the field strength meter are achieved. If these two maxima do not match, you need to slightly change the length of the antenna, and repeat its tuning again.

The matching device was placed in a case soldered from foil fiberglass with dimensions of 50 * 30 * 20 mm. When working from a stationary workplace of a radio amateur, the antenna can be placed in the window opening. When working in the field, the antenna can be hung from the upper end on a tree using a fishing line, as shown in Fig. 6. A 50 ohm coaxial cable can be used to power the antenna. Using a 75-ohm coaxial cable will slightly increase the efficiency of the antenna matching device, but at the same time, it will require the radio's output stage to be tuned to work with a 75-ohm load.

Figure 6. Mounting the antenna for field work

Foil Window Antennas

Based on the adhesive foil used in burglar alarm systems, very simple designs of VHF window antennas can be built. Such foil can be purchased already with an adhesive base. Then, having freed one side of the foil from the protective layer, it is enough just to press it against the glass and the foil instantly sticks securely. Foil without an adhesive base can be glued to glass using varnish or Moment type glue. But for this you need to have some skill. The foil can even be fixed to the window with adhesive tape.

With proper training, it is quite possible to make a high-quality solder connection of the central core and the braid of the coaxial cable with aluminum foil. Based on personal experience, each type of such foil requires its own flux for soldering. Some types of foil solder well even using only rosin, some can be soldered with soldering fat, other types of foil require the use of active fluxes. The flux should be tested on the particular type of foil used to make the antenna well in advance of installation.

Good results are obtained by using a substrate made of foil fiberglass for soldering and fixing the foil, as shown in Fig. 7. A piece of foil fiberglass is glued to the glass with Moment glue, the antenna foil is soldered to the edges of the foil, the cores of the coaxial cable are soldered to the copper foil of the fiberglass at a small distance from the foil. After soldering, the connection must be protected with a moisture-resistant varnish or glue. Otherwise, corrosion of this connection is possible.

Figure 7 Connecting Antenna Foil to Coaxial Cable

Let us analyze the practical designs of window antennas built on the basis of foil.

Vertical window dipole antenna

The scheme of a vertical dipole window VHF foil-based antenna is shown in fig. eight.

Figure 8. Windowed vertical dipole VHF antenna

The quarter-wave pin and counterweight are angled at 135 degrees to bring the antenna system's input impedance closer to 50 ohms. This makes it possible to use a coaxial cable with a wave impedance of 50 ohms to power the antenna and use the antenna in conjunction with portable radio stations, the output stage of which has such an input impedance. The coaxial cable should run perpendicular to the antenna on the glass for as long as possible.

Foil Loop Window Antenna

More efficient than a dipole vertical antenna, a VHF loop antenna, shown in fig. 9. When feeding the antenna from the side angle, the maximum of the radiated polarization is located in the vertical plane, when feeding the antenna in the lower corner, the maximum of the radiated polarization is in the horizontal plane. But at any position of the feed points, the antenna radiates a radio wave, with a combined polarization, both vertical and horizontal. This circumstance is very favorable for communication with portable and mobile radio stations, the position of the antennas of which will change during movement.

Figure 9. VHF frame window antenna

The input impedance of the window loop antenna is 110 ohms. To match this resistance with a coaxial cable with a characteristic impedance of 50 ohms, a quarter-wave section of a coaxial cable with a characteristic impedance of 75 ohms is used. The cable should run perpendicular to the axis of the antenna for as long as possible. A loop antenna has about 2 dB more gain than a dipole window antenna.

When making window foil antennas with a width of 6-20 mm, they do not require tuning and operate in a frequency range much wider than the amateur 145 MHz band. If the obtained resonant frequency of the antennas turned out to be lower than required, then the dipole can be adjusted by cutting off the foil symmetrically from its ends. The loop antenna can be adjusted using a jumper made from the same foil that was used to make the antenna. The foil closes the antenna sheet in the corner, opposite the feed points. Once configured, contact between the jumper and the antenna can be made either by soldering or by using adhesive tape. Such adhesive tape should press the jumper firmly enough against the antenna web in order to ensure reliable electrical contact with it.

Foil antennas can deliver significant power levels, up to 100 or more watts.

Outdoor vertical antenna

When placing an antenna outdoors, the question always arises of protecting the opening of the coaxial cable from atmospheric influences, using a high-quality antenna support insulator, moisture-resistant wire for antennas, etc. These problems can be solved by making a protected outdoor VHF antenna. The design of such an antenna is shown in Fig. ten.

Figure 10. Protected outdoor VHF antenna

A hole is made in the center of a plastic water pipe 1 meter long, into which a coaxial cable can tightly enter. Then the cable is threaded there, protrudes from the pipe, exposed at a distance of 48 cm, the cable screen is twisted and soldered at a length of 48 cm. The cable with the antenna is brought back into the pipe. Standard plugs are put on top and bottom of the pipe. Moisture-proofing the hole where the coaxial cable enters is not difficult. This can be done with automotive silicone sealant or fast curing automotive epoxy. As a result, we get a beautiful, moisture-proof protected antenna, which can work for many years under the influence of atmospheric influences.

To fix the vibrator and the antenna counterweight inside, you can use 1-2 cardboard or plastic washers tightly put on the antenna vibrators. The pipe with the antenna can be installed on a window frame, on a non-metal mast, or placed in another convenient place.

Simple coaxial collinear antenna

A simple collinear coaxial VHF antenna can be made from coaxial cable. A piece of water pipe can be used to protect this antenna from the weather, as described in the previous paragraph. The design of a collinear coaxial VHF antenna is shown in fig. eleven.

Figure 11. A simple collinear VHF antenna

The antenna provides a theoretical gain of at least 3 dB more than a quarter-wave vertical. She does not need counterweights for her work (although their presence improves the performance of the antenna) and provides a radiation pattern pressed to the horizon. The description of such an antenna has repeatedly appeared on the pages of domestic and foreign amateur radio literature, but the most successful description was presented in the literature.

Antenna dimensions in fig. 11 are indicated in centimeters for a coaxial cable with a velocity factor of 0.66. Most PE insulated coaxial cables have this shortening factor. The dimensions of the matching loop are shown in fig. 12. Without this loop, the SWR of the antenna system may exceed 1.7. If the antenna turned out to be tuned below the 145 MHz band, it is necessary to shorten the upper section a little, if it is higher, then lengthen it. Of course, the optimal tuning is possible by proportional shortening-lengthening of all parts of the antenna, but this is difficult to do in amateur radio conditions.

Figure 12. Dimensions of the matching loop

Despite the large size of the plastic pipe required to protect this antenna from atmospheric influences, the use of a collinear antenna of this design is quite reasonable. The antenna can be moved away from the building using wooden slats, as shown in fig. 13. The antenna can withstand significant power supplied to it up to 100 or more watts and can be used in conjunction with both fixed and portable VHF radios. The use of such an antenna in conjunction with low-power portable radios will give the greatest effect.

Figure 13. Installation of a collinear antenna

Simple collinear antenna

This antenna was assembled by me similar to the design of a car remote antenna used in a cellular radiotelephone. To convert it to the 145 MHz amateur band, I proportionally changed all the dimensions of the "telephone" antenna. As a result, an antenna was obtained, the circuit of which is shown in Fig. 14. The antenna provides a near-horizon directivity pattern and a theoretical gain of at least 2 dB over a simple quarter-wave pin. The antenna was powered by a coaxial cable with a characteristic impedance of 50 ohms.

Figure 14. Simple collinear antenna

The practical design of the antenna is shown in fig. 15. The antenna was made from a whole piece of copper wire with a diameter of 1mm. Coil L1 contained 1 meter of this wire, wound on a mandrel with a diameter of 18 mm, the distance between the turns was 3 mm. When the design is made exactly in size, the antenna practically does not require adjustment. It may be necessary to slightly adjust the antenna by compressing and stretching the turns of the coil to achieve a minimum SWR. The antenna was placed in a plastic water pipe. Inside the pipe, the antenna wire was fixed with pieces of foam. Four quarter-wave counterweights were installed at the lower end of the tube. They were threaded, and with the help of nuts they were fixed on a plastic pipe. Counterweights can be 2-4 mm in diameter, depending on the ability to cut threads on them. For their manufacture, you can use copper, brass, or bronze wire.

Figure 15. Construction of a simple collinear antenna

The antenna can be mounted on wooden rails on the balcony (as shown in Fig. 13). This antenna can withstand significant levels of power supplied to it.

This antenna can be considered as a shortened HF antenna with a central extension coil. Indeed, the antenna resonance in the HF band, measured with a bridge resistance meter, turned out to lie in the frequency region of 27.5 MHz. Obviously, by varying the diameter of the coil and its length, but at the same time maintaining the length of its winding wire, it is possible to ensure that the antenna operates both in the 145 MHz VHF band and in one of the HF bands - 12 or 10 meters. To operate on HF bands, four L/4 counterweights must be connected to the antenna for the selected HF band. This dual use of the antenna will make it even more versatile.

Experimental 5/8 wave antenna

When experimenting with 145 MHz radios, it is often necessary to connect the antenna under test to its output stage to check the operation of the radio's receive path or to tune the transmitter's output stage. For these purposes, I have been using a simple 5/8 - wave VHF antenna for a long time, the description of which was given in the literature.

This antenna consists of a section of copper wire with a diameter of 3 mm, which is connected at one end to the extension coil, and the other end to the tuning section. At the end of the wire connected to the coil, a thread is cut, and at the other end, a tuning section made of copper wire with a diameter of 1 mm is soldered. The antenna is matched to a coaxial cable with a wave impedance of 50 or 75 ohms by connecting to different turns of the coil, and there may be a slight shortening of the tuning section. The antenna circuit is shown in fig. 16. Antenna design is shown in fig. 17.

Figure 16. Scheme of a simple 5/8 - wave VHF antenna

Figure 17. Construction of a simple 5/8 wave VHF antenna

The coil is made on a Plexiglas cylinder with a diameter of 19 mm and a length of 95 mm. A thread is made at the ends of the cylinder, into which the antenna vibrator is screwed on one side, and on the other side it is screwed to a piece of foil fiberglass with dimensions of 20 * 30 cm, which serves as the "ground" of the antenna. On the back side, a magnet from an old speaker was glued to it, as a result of which the antenna can be attached to the windowsill, to the radiator, to other iron objects.

The coil contains 10.5 turns of wire with a diameter of 1 mm. The coil wire is evenly distributed over the frame. The tap to the coaxial cable is made from the fourth turn from the grounded end. The antenna vibrator is screwed into the coil, a contact lamella is inserted under it, to which the “hot” end of the extension coil is soldered. The lower end of the coil is soldered to the ground foil of the antenna. The antenna provides SWR in the cable no worse than 1:1.3. The antenna is tuned by shortening its upper part with wire cutters, which is initially slightly longer than necessary.

I have carried out experiments to install this antenna on a window pane. In this case, an aluminum foil vibrator, originally 125 centimeters long, was glued to the center of the window. The extension coil was used the same, and was installed on the window frame. Counterweights were made of foil. The ends of the antenna and counterweights were bent slightly to fit on the window pane. The view of the window 5/8 - wave VHF antenna is shown in fig. 18. The antenna is easily tuned to resonance by gradually shortening the vibrator foil with a blade, and gradually switching the coil turns to minimum SWR. The window antenna does not spoil the interior of the room and can be used as a permanent antenna for operation on the 145 MHz band from home or office.

Figure 18. Window 5/8 - wave VHF antenna

Efficient portable radio antenna

In the event that communication using a standard rubber band is not possible, a half-wave antenna can be used. It does not require a "ground" for its work and when working over long distances it gives a gain compared to a standard "elastic band" up to 10 dB. These are quite real numbers, given that the physical length of a half-wave antenna is almost 10 times longer than the "gum".

The half-wave antenna is powered by voltage and has a high input impedance that can reach 1000 ohms. Therefore, this antenna requires a matching device when used in conjunction with a radio with a 50 ohm output. One of the variants of the matching device based on the P-loop has already been described in this chapter. Therefore, for a change, for this antenna we will consider the use of another matching device made on a parallel circuit. In terms of their efficiency, these matching devices are approximately equal. The scheme of a half-wave VHF antenna together with a matching device on a parallel circuit is shown in fig. 19.

Figure 19. Half-wave VHF antenna with matching device

The circuit coil contains 5 turns of silver-plated copper wire with a diameter of 0.8 mm, wound on a mandrel with a diameter of 7 mm along a length of 8 mm. The setting of the matching device consists in setting the L1C1 circuit to resonance with the help of the variable capacitor C1, the connection of the circuit with the transmitter output is regulated with the help of the variable capacitor C2. Initially, the capacitor is connected in the third turn of the coil from its grounded end. Variable capacitors C1 and C2 must be with an air dielectric.

For the antenna vibrator, it is advisable to use a telescopic antenna. This will make it possible to carry the half-wave antenna in a compact folded state. It also makes it easier to set up the antenna with a real transceiver. During initial tuning of the antenna, its length is 100 cm. During the tuning process, this length can be slightly adjusted for better antenna performance. It is advisable to make appropriate marks on the antenna, so that later, from its folded position, install the antenna immediately to the resonant length. The box where the matching device is located must be made of plastic, in order to reduce the capacity of the coil to the "ground", it can be made of foil fiberglass. This depends on the actual operating conditions of the antenna.

The antenna is tuned using the field strength indicator. With the help of an SWR meter, tuning the antenna is advisable only if it does not work on the body of the radio station, but when using an extension coaxial cable together with it.

With double operation of the antenna on the radio station body and using an extension coaxial cable, two marks are made on the antenna pin, one corresponding to the maximum field strength level when the antenna is working on the radio station body, and the other risk corresponds to the minimum SWR when used together with the antenna extension coaxial cable. Usually these two marks are slightly different.

Vertical continuous antennas with gamma matching

Vertical antennas made from a single vibrator are wind resistant, easy to install, and take up little space. For their implementation, you can use copper tubes, aluminum power electrical wire with a diameter of 6-20 mm. These antennas can be easily matched with a coaxial cable with a wave impedance of both 50 and 75 ohms.

Very simple to implement and easy to tune is an inextricable half-wave VHF antenna, the design of which is shown in fig. 20. To power it through a coaxial cable, gamma matching is used. The material from which the antenna vibrator is made and the gamma matching must be the same, for example, copper or aluminum. Due to the mutual electrochemical corrosion of many pairs of materials, it is unacceptable to use different metals for antenna and gamma matching.

Figure 20. Continuous half-wave VHF antenna

If a copper bare tube is used to make the antenna, then it is advisable to adjust the gamma matching of the antenna using a closing jumper, as shown in Fig. 21. In this case, the surface of the pin and the gamma matching conductor is carefully cleaned and, using a bare wire clamp, as shown in fig. 21a achieve a minimum SWR in the coaxial antenna power cable. Then, at this point, the gamma matching wire is slightly flattened, drilled and connected with a screw to the antenna sheet, as shown in Fig. 21b. It is also possible to use soldering.

Figure 21. Setting the gamma - matching copper antenna

If an aluminum wire from a power cable in plastic insulation is used for the antenna, then it is advisable to leave this insulation to prevent corrosion of the aluminum wire by acid rain, which is inevitable in urban environments. In this case, the gamma matching of the antenna is adjusted using a variable capacitor, as shown in Fig. 22. This variable capacitor must be carefully protected from moisture. If it is not possible to achieve an SWR in the cable less than 1.5, then the length of the gamma matching must be reduced and the adjustment repeated again.

Figure 22. Adjusting the gamma-matching aluminum-copper antenna

With sufficient space and materials, a continuous vertical VHF wave antenna can be installed. The wave antenna works more efficiently than the half-wave antenna shown in fig. 20. The wave antenna provides a radiation pattern more pressed to the horizon than a half-wave antenna. You can match the wave antenna using the methods shown in Fig. 21 and 22. The design of the wave antenna is shown in fig. 23.

Figure 23. Continuous vertical wave VHF antenna

When making these antennas, it is desirable that the coaxial power cable be at least 2 meters perpendicular to the antenna. The use of a balancing device in conjunction with a continuous antenna will increase the efficiency of its operation. When using a balancing device, it is necessary to use symmetrical gamma matching. Balancing device connection is shown in fig. 24.

Figure 24. Connecting a balun to a continuous antenna

Any other known balancing device can also be used as an antenna balancing device. When placing the antenna near conductive objects, it may be necessary to slightly reduce the length of the antenna due to the influence of these objects on it.

Round VHF antenna

If the placement in space of vertical antennas shown in Fig. 20 and fig. 23 in their traditional vertical position is difficult, they can be placed by folding the antenna sheet into a circle. The position of the half-wave antenna shown in fig. 20 in the "round" version is shown in fig. 25, and the wave antenna shown in fig. 23 in fig. 26. In this position, the antenna provides a combined vertical and horizontal polarization, which is favorable for communications with mobile and portable radio stations. Although, theoretically, the level of vertical polarization will be higher with side feed of round VHF antennas, in practice this difference is not very noticeable, and side feed of the antenna complicates its installation. The side feed of the round antenna is shown in fig. 27.

Figure 25. Continuous round vertical half-wave VHF antenna

Figure 26. Continuous round vertical wave VHF antenna

Figure 27. Side feed of round VHF antennas

The round VHF antenna can be placed indoors, for example, between window frames, or outdoors, on a balcony or rooftop. When placing a round antenna in a horizontal plane, we get a circular radiation pattern in the horizontal plane and the operation of the antenna with horizontal polarization. This may be necessary in some cases when conducting amateur radio communications.

Passive "amplifier" portable station

When testing portable radios or working with them, sometimes there is not enough more “slightly” power for reliable communication. I made a passive "amplifier" for portable VHF stations. A passive "amplifier" can add up to 2-3 dB to the signal of a radio station on the air. This is often enough to securely open the squelch of the correspondent's station and ensure reliable operation. The design of the passive "amplifier" is shown in fig. 28.

Figure 28. Passive "amplifier"

The passive "amplifier" is a tinned coffee tin of a fairly large size (the bigger the better). A connector similar to the antenna connector of a radio station is inserted into the bottom of the can, and a connector for connecting to the antenna socket is soldered into the can's lid. 4 counterweights 48 cm long are soldered to the bank. When working with a radio station, this “amplifier” is switched on between the standard antenna and the radio station. Due to the more efficient "ground" and there is an increase in the place of reception of the strength of the emitted signal. Other antennas can be used with this "amplifier", for example, an L / 4 pin made of copper wire, simply inserted into the antenna socket.

Broadband survey antenna

Many imported portable radio stations provide reception not only in the 145 MHz amateur band, but also in the 130-150 MHz or 140-160 MHz survey bands. In this case, for successful reception in survey bands on which a twisted antenna tuned to 145 MHz does not work effectively, you can use a broadband VHF antenna. The antenna circuit is shown in fig. 29 and the dimensions for different operating ranges are given in Table. one.

Figure 29. Broadband VHF vibrator

Table 1. Dimensions of a wideband VHF antenna

To work with the antenna, you can use a coaxial cable with a characteristic impedance of 50 ohms. The antenna sheet can be made of foil and glued to the window. You can make the antenna fabric from an aluminum sheet, or by printing it on a piece of foil-coated fiberglass of suitable sizes. This antenna can receive and transmit in the specified frequency ranges with high efficiency.

Zigzag Antenna

Some long-distance VHF service radios use antenna arrays consisting of zigzag antennas. Radio amateurs can also try to use elements of such an antenna system for their work. A view of an elementary zigzag antenna included in the design of a complex VHF antenna is shown in fig. thirty.

Figure 30. Elementary zigzag antenna

The Zigzag Elementary Antenna consists of a half-wave dipole antenna that energizes the half-wave vibrators. Real antennas use up to five of these half-wave vibrators. Such an antenna has a narrow radiation pattern pressed to the horizon. The type of polarization emitted by the antenna is combined - vertical and horizontal. For the operation of the antenna, it is desirable to use a balancing device.

In antennas used in office communication stations, a reflector made of a metal mesh is usually placed behind elementary zigzag antennas. The reflector provides a one-way directivity of the antenna. Depending on the number of vibrators included in the antenna and the number of zigzag antennas included together, the required antenna gain can be obtained.

Radio amateurs practically do not use such antennas, although they are easy to perform for amateur VHF bands 145 and 430 MHz. For the manufacture of the antenna web, you can use an aluminum wire with a diameter of 4-12 mm from a power electric cable. In the domestic literature, a description of such an antenna, for the fabric of which a rigid coaxial cable was used, was given in the literature.

Antenna Kharchenko in the range of 145 MHz

The Kharchenko antenna is widely used in Russia for receiving television and in service radio communications. But radio amateurs use it to operate on the 145 MHz band. This antenna is one of the few that works very efficiently and requires little to no tuning. The diagram of the Kharchenko antenna is shown in fig. 31.

Figure 31. Antenna Kharchenko

Both 50 and 75 ohm coaxial cable can be used to operate the antenna. The antenna is broadband, operates in a frequency band of at least 10 MHz on the 145 MHz band. To create a one-way radiation pattern, a metal mesh is used behind the antenna, located at a distance of (0.17-0.22) L.

The Kharchenko antenna provides a beam width in the vertical and horizontal plane close to 60 degrees. To further narrow the radiation pattern, passive elements are used in the form of vibrators 0.45L long, located at a distance of 0.2L from the diagonal of the frame square. To create a narrow radiation pattern and increase the gain of the antenna system, several combined antennas are used.

145 MHz loop directional antennas

Loop antennas are one of the most popular directional antennas for 145 MHz operation. The most common on the 145 MHz band are two-element loop antennas. In this case, the optimal cost / quality ratio is obtained. The diagram of a two-element loop antenna as well as the dimensions of the perimeter of the reflector and the active element are shown in fig. 32.

Figure 32. VHF loop antenna

Antenna elements can be made not only in the form of a square, but also in the form of a circle, a delta. To increase the radiation of the vertical component, the antenna can be powered from the side. The input impedance of a two-element antenna is close to 60 ohms, and both 50 ohm and 75 ohm coaxial cable are suitable for working with it. The gain of a two-element VHF loop antenna is at least 5 dB (above the dipole) and the ratio of radiation in the forward and backward directions can reach 20 dB. When working with this antenna, it is useful to use a balancing device.

Circular polarized loop antenna

An interesting design for a circularly polarized loop antenna has been proposed in the literature. Antennas with circular polarization are used for communication via satellites. Dual power loop antenna with a phase shift of 90 degrees allows you to synthesize a radio wave with circular polarization. The power supply circuit of the loop antenna is shown in fig. 33. When designing an antenna, it must be taken into account that the length L can be any reasonable, and the length L / 4 must correspond to the wavelength in the cable.

Figure 33. Circular polarized loop antenna

To increase the gain, this antenna can be used in conjunction with a loop reflector and a director. The frame must be powered only through a balancing device. The simplest balancing device is shown in fig. 34.

Figure 34. The simplest balancing device

145 MHz Industrial Antennas

Currently on sale you can find a large selection of branded antennas for the 145 MHz band. If you have money, of course, you can buy any of these antennas. It should be noted that it is desirable to purchase one-piece antennas already tuned to the 145 MHz band. The antenna must have a protective coating that protects it from corrosion by acid rain, which can fall in a modern city. Telescopic antennas are unreliable in urban environments and may fail over time.

When assembling antennas, you must strictly follow all the instructions in the assembly instructions, and do not spare silicone grease for waterproofing connectors, telescopic connections and screw connections in matching devices.

Literature

1. I. Grigorov (RK3ZK). Matching devices in the 144 MHz range // Radio amateur. HF and VHF.-1997.-No. 12.-P.29.
2. Barry Bootle. (W9YCW) Hairpin Match for the Collinear – Coaxial Arrau//QST.-1984.-October.-P.39.
3. Doug DeMaw (W1FB) Build Your Own 5/8-Wave Antenna for 146 MHz//QST.-1979.-June.-P.15-16.
4. S. Bunin. Antenna for communication via satellite // Radio.- 1985.- No. 12.-S. twenty.
5. D.S.Robertson ,VK5RN The “Quadraquad” – Circular Polarization the Easy Way //QST.-April.-1984.-pages16-18.

So far, my experience with amateur radio has been limited exclusively to the shortwave bands (3-30 MHz). However, VHF bands of 2 meters are also available to radio amateurs. (aka "two", 144-146 MHz) and 70 centimeters (430-440 MHz). Working in these ranges has some nuances. If you just buy a VHF radio and yell CQ on the calling frequency from the balcony, then most likely you will not get the best experience. Here's what there is an underwater rake on VHF and how to avoid them, then we'll talk about it.

A bit of theory

It is required to say a few words about the terminology, as it is a bit confusing.

Ultrashort waves (VHF) is a huge frequency range from 30 MHz to 3000 GHz. It includes the ranges of meter waves (MV, wavelength 1-10 meters, or in frequencies from 30 to 300 MHz) and decimeter waves (UHF, wavelength 10-100 cm, frequency from 300 MHz to 3 GHz). MV is also known as VHF, very high frequencies (VHF, very high frequency). Similarly, another name for UHF is UHF, ultra-high frequencies (UHF, ultra high frequency). In English, the terms VHF and UHF are often used. For some reason, the abbreviations VHF and UHF have not really taken root in Russian, and they often say VHF, meaning both ranges. Further in the text, VHF will refer exclusively to the amateur radio VHF and UFH bands.

As you may know, SWs are refracted in the ionized layers of the atmosphere and return to Earth. Thanks to this, radio communications over thousands and even tens of thousands of kilometers are possible on HF. VHF doesn't work that way. For them, tropospheric passage is possible, but this phenomenon is relatively rare. Therefore, communication on VHF is usually possible over short distances, typically on the order of 100 km. When using "exotic" modes of communication (for example, via satellites), it is possible to make QSOs over much longer distances. But these types of connections deserve their own separate articles, so let's forget about them for now.

VHF may not be suitable for long-distance communications, but in terms of stability they have no equal. If there is a connection on VHF, then it is 24/7, regardless of the passage, and without any fading, lightning discharges, and so on. In addition, on VHF there are no problems with high noise levels on the air and pileups.

The presence of obstacles between correspondents (tall buildings, mountains, and so on) prevents radio communications on VHF. However, in urban areas, radio communications are possible by reflecting the radio signal from buildings. Let's say your balcony faces east and there is a tall building nearby. This building can play the role of a reflector, with the help of which it will be possible to contact a correspondent located in the west. Also, obstacles can be bypassed with the help of repeaters, which we will discuss below.

The wavelengths in the VHF bands are significantly shorter than in the HF bands. Due to this, VHF antennas are more compact. As a result, wearable and car radios are very popular. In addition, on VHF it is possible to build directional antennas with a high gain of a quite sane size.

To all that has been said, it should be added that VHF usually works in FM. This is not something that is very important, but is another difference from HF, where SSB is used.

Choosing a transceiver

For VHF, there are quite cheap walkie-talkies made in China, for example, from Baofeng. But with such walkie-talkies, a number of inconveniences await you - poor quality of the microphone and speaker, truncated functionality and an interface that is inconvenient for amateur radio purposes, short battery life, low case strength, and so on. But the worst thing is that such walkie-talkies are often not designed to work with an external antenna installed on the roof or balcony, but the antenna on the walkie-talkie itself extremely ineffective.

The problem is that Baofeng's are not full-fledged analog transceivers, but are built on the basis of the RDA1846 integrated circuit (datasheet). This scheme has a relatively small blocking dynamic range. This means that if you connect an external antenna to the walkie-talkie, the receiver will most likely be blocked by strong signals from local TV and radio stations. Theoretically, this is solved with the help of additional filters. But from a practical point of view, it is much easier to use a walkie-talkie from another manufacturer, for example, Yaesu, ICOM or Kenwood.

Important! With a good probability, you will not conduct any radio communications using any Baofeng UV-5R. Checked on personal bitter experience.

When choosing a transceiver, it will not be superfluous to look for reviews on the models you are interested in. Many radio amateurs post such reviews on YouTube. I previously provided a list of recommended YouTube channels in the note Let's go through the quest to get a call sign and register a RES. If a new transceiver does not fit into your budget, it makes sense to read the ads for the sale of used transceivers, for example, on the qrz.ru bulletin board.

That's how I got my radio, Kenwood TH-D72A (manual):

This is not new, but a very high quality device. It is especially interesting because it is almost the only real full duplex walkie-talkie. That is, as long as you are transmitting on the 2m band, the radio can continue to receive and play the signal on the second channel on the 70cm band (with DUP enabled). This is especially convenient when working with those "exotic" types of communication.

The radio also has GPS, APRS support, and probably some other useful features that I haven’t figured out yet. Like most portable radios, the Kenwood TH-D72A operates at no more than 5 watts. As we will soon see, this is quite enough for work on VHF.

fun facts! Although the walkie-talkie is no longer in production, Kenwood continues to release firmware updates for it.

Given the uniqueness of the walkie-talkie, the fact that the owner sold it with a KSC-32 charger, SMC-34 PTT, spare battery and carrying case, as well as extremely attractive price, the purchase was made without any hesitation. The transaction went smoothly - the device arrived quickly and in full working order.

Making an antenna

The default antennas of most portable radios are no good. The Kenwood TH-D72A antenna is no exception. The EU1KY Antenna Analyzer displays the following SWR graphs:

When constructing such graphs, it is necessary to hold on to the body of the antenna analyzer. The fact is that for normal operation, the antenna needs a human body that acts as a counterweight. If you do not hold on to the case, the graphics will turn out even worse. As you can see, the resonance missed a little on a deuce, only by “some” 15 MHz, and at 70 cm, the SWR does not fall below 2.4. In general, the antenna is pretty bad.

It was decided to make a full-size antenna for a range of 2 meters and place it on the balcony. Firstly, there will be no questions about its effectiveness for such an antenna. Secondly, it will be possible to work quietly on a deuce in winter, being warm and comfortable. Thirdly, for safety reasons, there should not be people near the antenna during transmission. Now this is not so critical, since I work on 5 watts. But in the future I can get a transceiver and more powerful.

A diagram of a suitable RG58 cable antenna was found in the blogs of Australian radio amateurs John, VK2ZOI and Andrew, VK1NAM:

The antenna is an ordinary dipole, only located vertically. Unlike HF, VHF requires polarization to be monitored. Usually radio amateurs use vertical polarization on VHF, which is why a vertical dipole is required. The cable core plays the role of the upper arm of the antenna, and the outer side of the cable screen plays the role of the lower arm. The cut-off choke consists of nine turns of cable on a 25 mm frame.

fun facts! Sometimes they work on VHF in the telegraph and SSB, while it is customary to use horizontal polarization. However, most modern VHF transceivers only support FM. CW and SSB are mostly supported in transceivers capable of both HF and VHF. Examples of such transceivers include the Yaesu FT-991A and the ICOM IC-7100. Digital modes of communication also work, with the difference that they are used for long-distance communications, and therefore polarization is not important.

First, a marching version was made:

The antenna was made a little longer than indicated in the diagram, and then cut to the minimum SWR on the range:

As you can see, the antenna has a relatively good resonance even at 70 cm. In this range, it operates on the third harmonic. This is not the best antenna for 70 cm, if only for the reason that the cut-off choke is completely not designed for this frequency. In particular, when the antenna is fed through a couple of meters of coaxial cable, the SWR graph changes significantly. But if necessary, the antenna allows you to make radio communications in this range (checked!).

After tuning, the antenna was completely placed in a PVC pipe. Both ends of the pipe were closed with pieces of sponge, and on top - covered with a lid. I printed the lid on a 3D printer, but a kefir lid or a piece of fiberglass would just as well fit. All holes, except the bottom one, were sealed with epoxy. I did not seal the bottom hole in case moisture somehow gets into the antenna. In this situation, she will have somewhere to drain.

The antenna was fixed on the balcony in the same way as I previously fixed the OPEK HVT-400B HF antenna:

Unlike HF, the RG58 cable is not suitable for feeding antennas on VHF. Instead, use RG213 or even lower loss cable. When using 10 meters of RG58, the signal attenuation at 144 MHz is 1.82 dB, and at 450 MHz it is 3.65 dB. For RG213, it is 0.86 dB and 1.73 dB, respectively. However, if the cable is short, just a couple of meters, then RG58 will do.

Let's go on air

The calling frequency in the range of 2 meters is 145.500 MHz. Just come in and make a general call, like on HF. They don't always answer. But if so, without much fanaticism, call in the morning before work and in the evening after, then people regularly answer. Of course, provided that you use a normal transceiver, an efficient antenna, and the correct cables as described above.

At 70 cm, everything is a little more interesting. The official general call frequency is 433.500 MHz. However, this frequency falls into the LPD range of 433.05-434.79 MHz and in Moscow there is a strong interference on it. The alternative frequency is 432.500 MHz. But this frequency falls within the range of 430-433 MHz, which is forbidden to be used within a radius of 350 km from the center of Moscow. As far as I could find out, there is an agreement among Moscow radio amateurs to use 436.500 MHz as a calling frequency. You can also try the so-called "pharmacy" frequency, 436.600 MHz.

fun facts! As on HF, on VHF there are radio hooligans, many of whom behave on the air, let's say, incorrectly. My life philosophy is that if you meet such a person on the air, don’t talk to him about anything and make sure that you stand as far as possible in frequency :)

Experiments show that in urban conditions the 2-meter range works noticeably better than the 70 cm range. Although radio communications can be carried out both there and there. I also do not rule out that the matter is in my antenna, which is not particularly designed to work at 70 cm.

We work through repeaters

Often radio communications on VHF are carried out through repeaters. A repeater is a device that receives your signal on one frequency and repeats it on another. Usually the repeater antenna is mounted somewhere high up where it can receive a signal from many hams, and the repeater transmits at high power. This is one of the reasons why it was said above that 5 watts is enough for VHF operation. The task is to reach the repeater. And it will already provide you with good power and coverage.

Often, repeaters are "opened" with a specific tone. A tone is a low frequency signal that is mixed into your voice when you transmit. The main tone transmission standards are CTCSS and DCS.

Tone is not a repeater password. It's more of a foolproof thing. Suppose a radio amateur is at an equal distance between two repeaters using the same frequencies. With the help of a tone, one of the repeaters can understand that a radio amateur is talking to him, and receive a signal. The second repeater, using a different tone, will understand that the message is not addressed to him, and will ignore the signal. Without a tone, a radio amateur would work simultaneously on two repeaters, and, unwittingly, would interfere with the work of colleagues.

The easiest way to find out about existing local repeaters is to ask local radio amateurs about them. You can also search the catalogs of repeaters, at least on the same qrz.ru. But the information in the catalogs is often either outdated or simply incorrect.

It is clear that in order to work through the repeater, the radio must be configured accordingly. Consider this setting on a specific example. A familiar radio amateur says that a repeater operates in your city with an input at a frequency of 145.050 MHz and a transmission at 145.650 MHz (channel R2), a tone of 88.5 Hz. You are using a Kenwood TH-D72A radio. The question is, how to get to the repeater?

Press VFO and set the frequency to 145.650 MHz. Go to MENU → Radio → Repeater → Offset Freq, enter here 0.6 MHz, that is, the difference between the frequent transmission and reception of the repeater. Press the green button F, and then SHIFT (located on the asterisk symbol, to the left of zero). The plus sign lights up on the screen. It means that when transmitting, the previously specified offset frequency will be added to the current frequency. But we need the frequency to be subtracted. Press F again, then SHIFT. The plus sign has changed to minus. You can check that everything is working as it should by quickly pressing and releasing PTT. During transmission, the frequency should automatically change to 145.050.

Setting the tone. To do this, press TONE (located on the number 8). The letter T lights up. It means that the radio will transmit the CTCSS tone, but will not require it to open the squelch. If you want the radio to check the tone when receiving, you can change it from T mode to CT mode by pressing TONE again. In the same way, you can switch to using DCS instead of CTCSS. Next, press the F button. Go to the choice of Tone Freq. Specify 88.5 Hz, save.

Now, in order not to lose the settings, press F, and then M.IN. Save to a memory cell. Now you can switch from VFO mode to MR mode and switch between saved channels. This is much more convenient than constantly adjusting frequencies and tones manually. If desired, the cell can be given a name in MENU → Memory → Name (only works in MR mode). By long pressing MR, you can switch to the continuous scanning mode of the stored channels.

If everything was done correctly, the people on the repeater should now be able to hear you. You can check the connection to the repeater by short pressing PTT. After you release PTT, the repeater will continue to transmit the carrier for some time, which you will hear. If there is no carrier, then either the repeater is not receiving your signal, or the tone has been set incorrectly, or the repeater is not working. If there is a carrier, then everything is fine.

fun facts! With some luck, it is possible to reach the repeater with 5 watts to an antenna located inside the house.

It is clear that when using a different walkie-talkie, the settings will be different. But the principle will be the same, and I think you can easily figure it out.

Conclusion

So, you went to VHF. Now what? You can stop there and just talk for life with radio amateurs living nearby. Or you can learn how to use APRS, conduct radio communications via satellites or EchoLink, receive SSTV from the ISS, install your own repeater, experiment with antennas, filters, amplifiers, digital voice modes (D-STAR, C4FM, DMR), transceivers from different manufacturers, or maybe and homemade. You might even want to try EME, that is, making radio communications by bouncing radio waves off the moon. In general, you have a range of frequencies. What you will do on it is limited mainly by your imagination.

73 and see you on VHF!

Addition: Replacing the stock antenna Kenwood TH-D72A is discussed in the post

Radio ranges and frequencies

In this article, we will briefly consider which frequencies are allocated for radio communications and which radio stations and which range should be considered when choosing equipment in a particular case. The article is presented in a free form, using simplifications in some concepts and details. It does not claim to be encyclopedic accuracy, but it will give a general idea of ​​the frequencies used in Russia and the radio communication equipment used.

Consider, What bands do radios work on? and why, in one case or another, different radio frequency ranges.

Shortwave range - 1-30 MHz

HF radio It is mainly used by the military, the Ministry of Emergency Situations, the Navy, forestry and environmental organizations for professional communication over long distances - from 150 to 8000 km.

The main disadvantages of the HF band are low noise immunity and the need to use overall antennas up to several tens of meters long. Pluses - absolute autonomy, long communication range and low cost compared to satellite communications.

Main equipment used: Icom, IC-M802., Vertex VX-1700, VX-1400, VX-1200/1210., Kenwood TK-90, Cordon R-12, Q-Mac HF 90M, Barrett PRC-2090, PRC- 2091, Karat, Angara.

Also, within 1-30 MHz, there are 9 sections of frequencies allocated for communication to radio amateurs. The main used HF amateur radio equipment is Kenwood, Icom, Yaesu, Elecraft transceivers. If for professional stable radio communications, the range is usually limited to 8000 km, then radio amateurs often conduct transcontinental radio sessions with their colleagues located on the other side of the globe.

Currently, the market for software-implemented radio - SDR equipment is gaining momentum. Software-based radio is beginning to be widely used in amateur radio, military and commercial applications. To date, Harris and Alcatel Lucent have already implemented several successful projects that use equipment based on SDR technology and cognitive radio (a radio system that can receive information about the features of its own operation and, based on this data, adjust its operating parameters). In the future, SDR technology has every chance of becoming a new standard in the telecommunications market.

Civil band - 27MHz

Conditionally called "range 27 MHz". Frequency range 25.6-30.1 MHz (officially allowed section - 26.965-27.860 MHz). Another name is CB range from the English abbreviation CB - Citizen Band.

Range of truckers on walkie-talkie this is the 15th channel, at 27.135 MHz, in amplitude modulation (AM) mode. The channel is actively used by truckers for communication on the highways. in big cities, walkie-talkie cb range 27 MHz, used by motorists to exchange traffic information. In different cities, different channels are used for urban communication. For example, in Krasnoyarsk it is channel 40, with a frequency of 27.405 MHz, in Kemerovo it is channel 27, with a frequency of 27.275 MHz. At the frequencies of urban auto channels, frequency modulation (FM) is used.

Also, radio stations of this range are used by small taxi firms and cargo carriers, rapid response teams of security companies and utilities. Despite the affordability of the equipment, and the fact that, according to the Decree of the Government of the Russian Federation of October 13, 2011 No. 837, 27 MHz radios are not subject to registration, it is necessary to take into account the fact that the civil band is subject to large atmospheric and industrial interference and the use walkie-talkieCB band for commercial purposes is not suitable for enterprises where high-quality radio communications are needed. Portable CB radios, due to the small radius of action and relatively large dimensions, they have not received much distribution and are used mainly in loading and unloading operations or in truck parking lots.

Most of the CB radio stations available in Russia are presented in our online store.

CB radio to buy which you can in our online store are presented in .

Low-Band range - 33-57.5 MHz

This is the lower section of the VHF mobile radio band.

Due to the large influence of industrial interference in cities and interference from TV broadcast transmitters, this range is used mainly in rural areas. The main users, since the times of the USSR, are ambulance stations and agricultural enterprises. To date, most of the world's manufacturers have stopped producing radio stations for these frequencies. Equipment for the Low-Band range, at the moment, is offered by domestic manufacturers - the Granit and Vebr companies. In warehouses, you can still find radio stations from famous brands: Motorola GP340, GM360., Vertex Standard VX-3000L. Alinco, Inc. remains the only available foreign manufacturer of equipment in the 33-57.5 MHz range. The company offers the DJ-V17L portable radio and DR-135LH and DR-M06R car (base) radios.

Air range - 118-137 MHz

Aircraft carry out radio exchange between themselves and with ground services in this frequency range. Unlike most other types of VHF communications, amplitude modulation is used. Popular equipment for the air range -

wearable aviation range radios:

156.8375-174 MHz - mobile and fixed terrestrial communications.

In accordance with the basic law "On Communications" dated July 07, 2003 No. 126-FZ, in order to organize radio communications in this range, it is necessary to obtain permission from the Federal State Unitary Enterprise "GRCHTs". If it is necessary to obtain frequencies, we can provide consulting and accompanying support in obtaining permits.

High noise immunity and good signal transmission have made the 136-174 MHz band the most popular among users and equipment manufacturers. Most of the popular models of VHF radios and antennas are presented in our store. walkie-talkiesVHF band in our shop are presented in .

River range - 300 MHz

Used for communication on inland waterways.

Operating frequencies of walkie-talkies are in the range of 300.0125-300.5125 MHz and 336.0125-336.5125 MHz.

River Range Walkie Talkie comes with pre-installed channels dedicated to communication with ships and shore services, for one purpose or another.

Channel radio frequencies- their numbers and purpose are established by the "Instructions on the organization of ship radio communications in the basin (region)", approved by the River Fleet Service of the Ministry of Transport of the Russian Federation and agreed with local authorities of the State Supervision of Radio Communications. So, the main channels are:

Channel 2 (300.05 MHz) - for communication between ships;

Channel 3 (300.1 MHz) - for communication with gateway controllers;

Channel 4 (300.15 MHz) - for communication with other river fleet services;

Channel 5 (300.2 MHz) - for calling ships, coordinating the order of divergence and overtaking when maneuvering and transmitting distress signals.

Channel 25 and 43 (336.2 MHz and 300.125 MHz) are commonly used for communication between yachts.

All radio stations installed on ships, on inland waterways, must necessarily have the Permission of the River Register of Russia (RRR) and the Certificate of the Ministry of Communications, regardless of their ownership and whether these radio stations are the main or additional equipment.

According to the frequency allocation approved by the International Telecommunication Union (ITU), all over the world for communication between ships (rivers and seas) frequencies in the range of 156-162 MHz are used. The 300 MHz river band is used only in Russia and the choice of equipment offered for this band is small. Popular river radio stations: Radioma-300, Vertex Standard VX-451/VX-454,.

VHF range - 400-470 MHz

In foreign sources, the range is referred to as UHF, the name of which is derived from capital letters Ultra High Frequency.

The distribution features of UHF frequencies make it possible to recommend this range for use in dense urban areas, in the mountains. In the conditions of a forest area, radio stations at 400 MHz are inferior to radio stations in the 136-174 MHz range.

In the range, frequency bands are allocated for professional use, for radio amateurs and for unlicensed use by everyone.

Radio frequencies, whose operation, in accordance with the basic law "On Communications" dated July 7, 2003 No. 126-FZ, is possible only if there are permits:

420-430 MHz - mobile and fixed terrestrial communications;

430-440 MHz - amateur radio band;

440-470 MHz - mobile and fixed terrestrial communications.

If it is necessary to obtain frequency ratings, we can provide consulting and accompanying support in obtaining permits.

Sections of the range, which, according to Decree of the Government of the Russian Federation of December 31, 2004 No. 896, do not require permits - allowed radio range(unlicensed frequencies):

433.075-434.775 MHz - LPD ("Low Power Device") range. Standard frequency grid of 69 denominations, with a step of 25 kHz;

Often in the characteristics of radio stations it is indicated as operating ranges VHF and UHF Consider what it is and what is the difference between them.

These abbreviations denote the two most common VHF communication bands.
the VHF range corresponds to the section from 136 to 174 MHz
the UHF range corresponds to the section from 400 to 512 MHz

In everyday life, radio amateurs also call these ranges "two" (VHF) and "seventies" (UHF), such names are given to these bands in accordance with the wavelength, which for VHF is about 2 meters and for UHF about 70 centimeters.

VHF- a range in which there are sections reserved for many government agencies, space communications and radio amateurs.

The main advantage of this range in comparison with UHF is a large communication range, especially outside the city. Walkie-talkies of this range work perfectly both in rural areas, in the forest, and in multi-storey buildings. The disadvantages of working in this frequency range include the absence of license-free areas, a relatively small area allocated for radio amateurs - from 144 to 146 MHz on a primary basis.

Due to the fact that these are quite low frequencies, effective antennas for this band are larger than for UHF, and in the case of walkie-talkies this is a significant problem that limits the use of VHF when working with portable radios. And of course, you can’t work on it without having a radio amateur category!

Below is a table with the frequency grid allocated for amateur radio communications. According to the decision of the SCRF dated July 22, 2014 No. 14-26-04, the range from 144 to 146 MHz is allocated to the amateur radio service on a primary basis. Radio amateurs of the 4th category have the right to operate at these frequencies with a power of not more than 5 W, the 2nd and 3rd by 10 W, and the 1st category by 50 W (for EME and MC communications of the first category it is allowed to use up to 500 W ). For voice communication with frequency modulation, frequencies from 145.206 MHz to 145.594 MHz are allocated.

UHF- is considered a range "for the city" and allows you to get a reliable connection in high-rise buildings. Ideal for establishing communication over relatively short distances, due to the high frequency of the antennas of portable radios in this range, they are compact in size without sacrificing efficiency. But at the same time, this range is not suitable for open spaces and forests due to greater attenuation in the forest and poor ability to bend around the terrain compared to VHF.

According to the decision of the SCRF dated July 22, 2014 No. 14-26-04, the range from 430 to 440 MHz is allocated to the amateur radio service on a secondary basis. Radio amateurs of the 4th category have the right to operate at these frequencies with a power of not more than 5 W, 1st, 2nd and 3rd no more than 10 W (at frequencies from 433 MHz to 440 MHz), Also radio amateurs with 1st category is allowed to operate at 500 watts in a limited range (for EME and MC communications). At frequencies of 430.000-433.000 MHz, you can only work with a power of not more than 5 W for all categories without exception.

As can be seen from the frequency table below, there is much more free space on UHF allocated for amateur communications than on VHF, which also indirectly affects the predominant use of this range in large cities.

Also, do not forget that there are two unlicensed bands on the UHF frequency section

Information has surfaced on an agenda item for the 2023 World Radiocommunication Conference (WRC-23) that proposes consideration of the 144-146 MHz frequency band, including a possible redesignation as an application as a core band for the aeronautical mobile service, and few people objected at a meeting of the European Conference of Postal and Telecommunications Administrations (CEPT). The Team A project group where this issue was considered is responsible for some aspects of the CEPT WRC positions and the meeting was held June 17-21 in Prague, Czech Republic. The proposal submitted by France aimed at reassigning the 144-146 MHz amateur radio band will be part of a broader consideration of the aeronautical mobile bands. Another issue raised at the meeting was the sharing of the 1240-1300 MHz amateur radio band with the European Galileo GPS system.

“We have heard that only one administration (Germany) opposed the proposal to put the 144 MHz amateur band on a secondary basis – and no other,” said a spokesman for the UK Microwave Group after the meeting. Otherwise, this agenda item would have been rescheduled for the CEPT Conference Preparatory Group (CPG) meeting in August.

The International Amateur Radio Union (IARU), which was represented at the Prague meeting, expressed "serious concern" about any proposal that would include consideration of the 144-146 MHz band from an aeronautical mobile aspect in the proposed agenda item. Moreover, at the conference they intend to consider the issue of reassigning the entire 2-meter band in the 1st ITU Region. IARU is committed to making every effort to fully protect the interests of amateur radio stations and to enlist the support of the necessary regulators for their representation.

IARU Region 1 President Don Beattie, G3BJ, stated ahead of the meeting that the IARU will "vigorously promote its opposition within the Regional Telecommunications Organizations (RTOs) and the International Telecommunication Union (ITU) to ensure that that this band will remain the main one for radio amateurs.

The 144-146 MHz band in the worldwide frequency allocation is the only VHF band assigned to the amateur and amateur-satellite services on a primary basis. This widely used segment of the amateur radio bands is used by a large number of users, repeaters and satellite stations, including the ISS.

According to the minutes of the meeting, the proposal does not justify the redefinition of 144-146 MHz and the IARU considers that sharing with airborne systems is likely to be difficult and will limit the development of the amateur and amateur-satellite services in this band. The IARU recommended that alternative proposals be developed that could provide additional radio spectrum for aeronautical applications, without having to hang the “sword of Damocles” over “two” radio amateurs.

The IARU is expected to inform community members to discuss the French proposal with their governments before the August CEPT-CPG meeting. And France could try to introduce the same proposal to explore 144-146 MHz for aeronautical use in other RTOs.

In the meantime, further discussions by the preparatory group on the 23cm study proposal are expected before the meeting in August. This proposal was made following reports of interference with the Galileo navigation system, but the IARU stated that it was aware of only "a few cases" of interference with the E6 Galileo signal at 1278.750 MHz. In the meantime, work on this issue will continue in other specialized CEPT forums.