Delta antennas. Electrical diagrams for free


Delta type antennas have long been used by radio amateurs. It is convenient to place it in any way and vertically if there is sufficient height and when there is no space on the roof, but it happens that it is not possible to place the antenna even at an angle of 45 degrees. Therefore it is proposed different variants implementation of the “Delta” antenna and its placement and fastening.

Figure 1 shows the classic placement of the antenna with a sufficient suspension height.

You cannot position the antenna at an angle to the ground; you can position it horizontally relative to the surface of the earth (Fig.2). To match the input impedance of the antenna and the supply feeder, a transformer is used, which is made of RK 75 cable, 13.94 m long.

If you have enough space to position the Delta at an angle of 45 degrees and get the maximum benefit from this antenna, then Figure 3 shows a diagram of the antenna placement with dimensions. Coordinating the antenna with the RK 75 power cable does not cause any particular difficulties. Antenna tuning is reduced by setting it to the middle frequency of the range by changing the perimeter of the “Delta” frame, and tuning by SWR by changing the angle of inclination relative to the ground.

If the height of the suspension is insufficient, an option is offered with the location of the “Delta” antenna in the horizontal and vertical planes in Fig. 4, while the radiation of the antenna will be directed towards the open arms of the antenna.

If there is a good difference in heights, if you live in a 9 or 12 storey building, in the yard or nearby there are 4 or 5 storey buildings, you can make a directional antenna from 2 “Delta” antennas, its diagram is shown in Fig. 5. This antenna has all the properties of a directional antenna and has a gain in the radiation direction of up to 8 dB. The antenna is structurally located on guy wires broken by insulators. Powered coaxial cable RK 75.

If there are nearby buildings of the same height, you can make an antenna from 3 “Delta” antennas, Fig. 6. The gain of this antenna up to 9.5 dB is also powered without any matching devices since the input impedance of this antenna is 75 ohms. The perimeter of “Delta” is R = 85.8 meters, Z = 83.3 meters, D = 80.8 meters. The distance between R and Z = 25 meters, and between D and Z = 25 meters. Structurally, the antenna is stretched with guy ropes made of nylon cable with a diameter of 8 - 10 mm with turnbuckles.

The antenna shown in Fig. 7 is one of a series of compromises: – low antenna height of 11 meters and the desire to use it in a wide frequency band. To match the input impedance of the antenna, an open line with a resistance of 300 ohms is used, so you can work through such an antenna only through a tuner, this will not only allow you to match correctly, but also makes it possible to use it in a multi-band version.

Seal

The topic of this article is inspired by the Delta N311-01A antenna (active with amplifier) ​​that came in for repair. The design of the antenna is such that if the vibrators for receiving the meter range are removed (which will significantly reduce its dimensions), then it can only be used as an antenna for the decimeter range.

Delta N311-01A is a version of the Delta 311-01 antenna without an amplifier. An all-wave television antenna with a broadband amplifier is used in conditions of unsatisfactory reception in the VHF and UHF ranges. Receives analog and digital television broadcasting, in the frequency range 48.5-890 MHz and consisting of decimeter antenna and a meter range vibrator. The antenna has uniform gain over the entire frequency range.

The design of the antenna is quite simple and therefore it is quite accessible for repetition. The main elements that make up the antenna are: decimeter part; vibrator MV; matching board and signal amplifier. Complex elements include: a matching board and an amplifier, but you can do without them by installing an SWA type amplifier.

The decimeter part is a log-periodic antenna with 20 vibrators.

A log-periodic antenna (LPA) consists of two pipes located one above the other, to which the vibrator arms are attached alternately.

The cable is connected to the LPA without a special matching device as follows. A cable with a characteristic impedance of 75 Ohms is inserted into the down tube at one end and exits at the other. The cable braid is soldered to the end of the lower pipe, and the central core is soldered to the end of the upper pipe.

Depending on the wavelength of the received signal, several vibrators are excited in the antenna structure, the dimensions of which are closest to half the wavelength of the signal. At a given signal wavelength, only one trio of vibrators is excited, while the rest are detuned and do not affect the operation of the antenna. The antenna gain drops somewhat, but the bandwidth is much wider.

It is useful to know that the smoother the surface of the conductors from which the antenna is made, the higher its quality indicators (higher the quality factor).

The MV antenna is designed extremely simply - these are two vibrators 110 cm long, attached to protective housing amplifier

The matching board and amplifier are hidden in a sealed housing.

The balancing device is used to match meter and decimeter range antennas with an amplifier.

Dimensions

For those who want to make a copy, I provide the dimensions of the UHF and HF antennas.

All antenna dimensions are given in millimeters. The diameter of the tubes is 12 mm, the diameter of the vibrators is 4 mm, the gap between the tubes is 6 mm. At the beginning of the antenna, the tubes are secured with plastic; at the point of attachment to the mast, the tubes are soldered.

The antenna gain can be increased somewhat further by adding a reflector behind the antenna mounting device.

Among radio amateurs, the loop antenna with a perimeter of 84M is very popular. It is mainly tuned to the 80M band and with a little compromise it can be used on all amateur radio bands. This compromise can be accepted if we are working with a tube power amplifier, but if we have a more modern transceiver, things will no longer work there. We need a matching device that sets the SWR on each band, corresponding normal operation transceiver. HA5AG told me about a simple matching device and sent me a short description of it (see picture). The device is designed for loop antennas of almost any shape (delta, square, trapezoid, etc.)

Matching device HA5AG
To enlarge, click on the diagram

Short description:
The author tested the matching device on an antenna, the shape of which is almost square, installed at a height of 13M in horizontal position. The input impedance of this QUAD antenna on the 80M band is 85 Ohms, and on harmonics it is 150 - 180 Ohms. The characteristic impedance of the supply cable is 50 Ohm. The task was to match this cable with the input impedance of the antenna 85 - 180 Ohm. For matching, transformer Tr1 and coil L1 were used.

In the 80M range, using relay P1, we short-circuit coil n3. In the cable circuit, coil n2 remains switched on, which, with its inductance, sets the input impedance of the antenna to 50 Ohms. On other bands P1 is disabled. The cable circuit includes coils n2+n3 (6 turns) and the antenna matches 180 Ohm to 50 Ohm.

L1 – extension coil. It will find its application on the 30M band. The fact is that the third harmonic of the 80M band does not coincide with the permitted frequency range of the 30M band. (3 x 3600KHz = 10800KHz). Transformer T1 matches the antenna at 10500 KHz, but this is not enough, you also need to turn on the L1 coil and with this connection the antenna will already resonate at a frequency of 10100 KHz. To do this, using K1, we turn on relay P2, which at the same time opens its normally closed contacts. L1 can also serve in the 80M range, when we want to work in the telegraph section. On the 80M band, the antenna resonance band is about 120 KHz. To shift the resonance frequency, you can turn on L1. The included coil L1 significantly reduces the SWR at the 24 MHz frequency, as well as at the 10 M range.

The matching device performs three functions:
1. Provides symmetrical power to the antenna, since the antenna web is isolated at HF ​​from the ground through transformer coils Tr1 and L1.

2. Matches the impedance described higher way.

3. Using coils n2 and n3 of transformer Tr1, the antenna resonance is placed in the corresponding, permitted frequency bands by range. A little more about this: If the antenna is initially tuned to a frequency of 3600 kHz (without turning on the matching device), then on the 40M ohm band it will resonate at 7200 KHz, on the 20M ohm band at 14400 KHz, and on the 10M ohm band it will resonate at 28800 KHz. This means that the antenna needs to be extended in each range, and at the same time higher frequency range, the more extension it requires. Just such a coincidence is used to match the antenna. Transformer coils n2 and n3, T1 with a certain inductance, the more the antenna extends, the higher the frequency of the range. In this way, on the 40M band the coils are extended to a very small extent, but on the 10M band they are extended to a significant extent. A correctly tuned antenna is placed in resonance by the matching device on each band in the region of the first 100 kHz frequency.
The positions of switches K1 and K2 by range are indicated in the table:

If the input impedance of the antenna on the 80M band is set not within 80 - 90 Ohms but within 100 - 120 Ohms, then the number of turns of coil n2 of transformer T1 must be increased by 3, and if the resistance is even higher, then by 4. The parameters of the remaining coils remain unchanged .

Photo: HA5AG matching device
Click on the photo to enlarge

73! de HA5AG

Translation: UT1DA
source - (http://ut1da.narod.ru)
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V. DAVYDOV (UW9WR), UfaThe disadvantage of the previously described electronic switches antennas is a significant attenuation in the receiving mode, reaching 45-50% (especially in the ranges of 21 and 28 MHz). Switch, scheme which is shown in the figure, provides an attenuation of no more than 10%. When manufacturing the switch, it is necessary to isolate the body of the output capacitor of the P-circuit (in the diagram - C4) from the chassis with a fluoroplastic or polystyrene gasket 5 mm thick. The antenna is connected to the Gn1 socket, the receiver input - to nest GN2.RADIO No. 7, 1975 p.15...

For the scheme "MINIATURE DIRECTIONAL ANTENNA FOR 144-146 MHz RANGE"

For the "ALL METAL DELTA ANTENNA" circuit

For the diagram "Double square antenna design"

For the "DUAL BAND UHF ANTENNA" circuit

For the "144 MHz VERTICAL ANTENNA" circuit

For the circuit "Antenna amplifier for a radio transmitter"

RF power amplifiersAntenna amplifier for radio transmitter Scheme antenna amplifier does not require any special explanation. The amplifier is mounted in a casing made of galvanized metal 1 mm thick, dimensions 120x60x30 mm. An aluminum plate of the same size, 10 mm thick, is screwed to the bottom of the body. Design printed circuit board the same as in [Z]. The drawing is not shown here, because The board configuration is highly dependent on the type of parts used. It is only important that all connections are as short as possible and reliable thermal contact of transistor VT1 with the heatsink plate is ensured. Details. Relay K1, K2 - RES-15(002). Connectors XW1, XW2 - SR-50-73F. Resistors - MLT. Capacitors - CT, KM; S16.S17-KPK-MP. Inductors: LI - inductor DPMZ-3 10 μH; L2 - 14 turns on a resistor MLT-0.5 150 Ohm PEV-2 0.35 turn to turn. L9, L11 -DPM1-0.1 56 µH. The remaining coils are frameless, wound with PEV-2 0.8 wire on a 5.5 mm mandrel. The number of turns depending on the range is given in the table. The same table shows the capacitances SZ...S15 (pF). RangeL3L4L516L718L1C3С4С5С7С8С9С10С11С12С14С1527. ..29 MHz346999856047011068470200...27027027011Q682750 Hz23577763302706839270120...150150150683915The configuration of the antenna unit is contained in the configuration using C16, C17 of the input circuit of the antenna amplifier for the maximum sensitivity of the receiver radio stations. By connecting an HF generator to input A5...

For confident reception television programs An antenna is required. Since the start television broadcasting were constantly being developed Various types receiving antennas. Thanks to the accumulated experience in the theory of radio signal reception and the improvement of antenna design methods, several types are currently widespread receiving devices, which differ in gain, directivity, and frequency range.

Antenna requirements

All TV antennas must meet certain requirements, which are often contradictory, but failure to comply with them leads to the antenna turning into a useless structure:

  • frequency range;
  • directional pattern;
  • gain;
  • dimensions.

The most problematic parameters are gain and directivity. In most cases, increasing the gain narrows the directivity. On the one hand, this is good, since it eliminates the possibility of receiving an interfering signal from another direction, a reflected signal or interference. On the other hand, a narrowly directional antenna requires precise tuning to the transmitting station, and the slightest deviation from the given direction, for example, in strong winds and a high mast, sharply reduces the quality of reception.

No less important parameter- frequency range. The vast majority of antennas have the highest gain within a narrow frequency band, corresponding in a particular case to one television channel. The operating range is expanded by reducing the gain. And since television broadcasting is carried out over a wide range of frequencies, designing a universal antenna becomes a very difficult task.

The television broadcast frequency range is divided into two subranges:

  • from 1st to 6th channel – meter range (49-250 MHz);
  • from the 21st to the 69th channel - decimeter range (474-858 MHz).

The difference in wavelengths in the meter and decimeter ranges has led to the fact that devices for receiving meter and decimeter programs have different design features, mainly related to dimensions.

Digital television operates in the decimeter range. Stable reception of decimeter waves is possible only in direct visibility from the transmitting antenna. On long distances it is necessary to either increase the height of the antenna or increase the gain.

Meter range signals can bend around the surface of the earth, so the area of ​​reliable reception is much larger.

Antenna types

The most widely used antennas are the “Wave Channel” type. They have a narrow radiation pattern and high gain, which are directly related to the number of elements and, accordingly, to the length of the structure. But, as the length increases, the weight increases and the mechanical strength of the structure decreases. The frequency range is also narrowed.

The log-periodic antenna is smaller in size. It has a somewhat similar design, but differs in a different operating principle.

Both types of antennas require high precision during manufacture, which increases with the number of elements. The wave channel and log-periodic antenna are most widely used for operation in the decimeter range. They are unsuitable for the meter range because they will have unacceptable dimensions.

For meter waves, the half-wave dipole is most often used. Its main advantage is ease of manufacture and low requirements for manufacturing accuracy. Such antennas have a radiation pattern in the form of a figure eight. That is, they can receive a signal from two opposite directions. By bending the elements in one direction, you can weaken one of the lobes of the diagram and increase the gain in the direction of bending the elements.

Universal Delta

Many enterprises have launched the production of the universal Delta antenna, which is designed to receive signals in almost the entire range, from meter to decimeter.

This antenna, both external and indoor, has several design options and, accordingly, some differences in parameters. The main difference for indoor and outdoor versions is overall dimensions and the number of work items. Of course, an internal indoor antenna will have worse parameters than an external one, but, due to its compactness, it is quite acceptable when located near the transmitting center.

Delta antenna design

This device is a combination of a half-wave dipole for receiving meter and wave channels and log periodic antenna for the high-frequency range of decimeter waves.

Both components are coordinated with each other in such a way as to minimize mutual influence and improve the quality of reception. It is important that only one cable is used for both bands.

The Delta outdoor antenna has the following average characteristics:

  • frequency range – MV, UHF;
  • gain – 3-14 dB;
  • protective factor – 12 dB;
  • characteristic impedance of the cable is 75 Ohms.

The protective coefficient shows the amount of attenuation of the signal coming from the rear side opposite to the main direction of reception. This value applies only to the decimeter part of the antenna. Gain spread shows the difference in gain for different channels, since it is impossible to create universal device with linear characteristic. The minimum gain here falls on MV channels, broadcasting on which tends to decrease.

The best values ​​of protective action in the UHF range have devices equipped with a reflector located between the meter and decimeter parts. The reflector is a grating that attenuates the signal from the rear lobe of the radiation pattern, while slightly increasing the gain.

The given parameters refer to passive antennas that do not have a signal amplifier. Thus, their scope of application is limited to those areas where there is a direct line of sight to the transmitting station.

The use of an amplifier structurally located in close proximity to the antenna makes it possible to increase the overall gain in the UHF range to 20-27 dB. Outdoor antenna with such amplification it makes it possible to receive television programs in almost any area.

The narrow directivity range and high gain make Delta antennas attractive for digital TV, which is broadcast primarily in the UHF range.

How to connect the antenna correctly

Connecting the Delta antenna to a TV or tuner is done in the same way as other antennas. A regular plug must be connected to the split end of the cable if the antenna is passive, or a power supply adapter if used active antenna with reception amplifier. When connecting the cable and plug, it is important to avoid shorting the screen and the central core.

The cable is connected according to the antenna manufacturer's instructions. The connection documentation must include a connection diagram. The design must provide for sealing of the cable entry and connection points. Otherwise, you should perform sealing yourself, based on the capabilities of the design. If moisture gets on the amplifier, it will almost instantly damage it, and the cable screen, thanks to the capillary effect, sucks water along almost the entire length of the cable. It is impossible to dry a wet cable, and in the very near future it will fail due to corrosion of the shielding braid.

Important! The main reason for the failure of the receiving device or Bad quality signal lies in improper cutting and fastening of the cable, when the central core has contact with the conductors of the shielding braid.

Antennas usually do not come with a cable, so you will have to purchase it separately. When choosing a cable, you need to pay attention to the characteristic impedance. Pluggable tv cable has a resistance of 75 ohms. Any other type of cable for connecting the antenna is not suitable. The shielding braid must be dense and uniform, otherwise interference may occur. When choosing between cables of different thicknesses, preference should be given to the thicker one, since it introduces less attenuation, which can be critical when the distance to the antenna is large (for example, installed on a high mast).

Important! The cable to the TV is not just an electrical wire. It must be solid, so it is better to purchase it with a reserve, since you can always trim or hide the excess, and when building a short one, signal losses greatly increase, since the absence of inhomogeneities in the conductors and insulation is important. The biggest nuisance when using a spliced ​​cable is the appearance of a reflected signal in it, which leads to ghosting and blurriness of the image on an analog TV or loss of the digital signal.

How to save on your purchase

More precisely, we are not talking about how to reduce costs when buying an antenna, but how not to pay more. Many manufacturers offer modified wave channel elements in the Delta antenna. There are various variations of zigzag conductors, even cut lengthwise and spread apart.

We can safely say that these tricks are nothing more than a marketing ploy designed to attract buyers by appearance. It is doubtful that the manufacturer who redesigned the design would have taken rigorous measurements. No actions with the shape of the elements lead to an increase in the gain. On the contrary, the calculation even conventional antenna extremely complex, what can we say about the openwork designs that can be found in stores or on the market. Such antenna designs have greater weight and lower mechanical strength. When manufacturing them, it is more difficult to accurately maintain all dimensions, so their characteristics will most likely have little in common with those declared.

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