|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Antenna or amplifier? Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas This material is useful for those who would like to spend money to improve the quality of communication with maximum efficiency. It looks at various ways to achieve the decibels everyone needs and provides an estimate of the costs of obtaining them. Not all, but many radio amateurs, sooner or later face the problem of improving the quality of communication. In this case, many questions arise, but the main ones, as a rule, are only two: buy a powerful linear amplifier or improve the antenna system? Both of them can be classified as philosophical in many respects. Well, we will try to consider them in detail from the point of view of material costs and ergonomics, i.e. - improving the consumer qualities of the radio system and, based on these reflections, we will try to give advice that some of you may even try to use. In recent years, there has been a steady trend in the world to reduce the power of transmitters where such a possibility exists. This is due to the introduction of a new direction in the development of modern technology - energy saving, which allows saving constantly depleting mineral reserves, which, in turn, are used to produce electrical energy, and the increasingly loud statements of the "green" about the dangers of any radio emission. These facts, of course, are not decisive when choosing a way to improve communication efficiency for millions of radio amateurs around the world. They (including us) always want to go further, more, more powerful, even if they have to dress in lead bathrobes! Someone needs the first DXCC, someone needs 9V WAZ, and so on ad infinitum! The accumulation of awards that glorify ourselves, for some, becomes the goal of life # 1! With age, this becomes a habit, and it is no longer possible to stop. When a radio operator wants to stand out from the rest, the first thing that comes to mind is to make an unusually powerful amplifier. However, upon detailed consideration of the problem, the facts indicate that installing an overly powerful linear amplifier to increase the level of the emitted signal is far from the optimal solution. One of these facts is the price / quality ratio of the result achieved. Well, in our country, the problem of the price of pleasure remains, perhaps, the main one in this matter. Before further consideration of the issue, let's make a small digression for a brief acquaintance with a certain device: the so-called S-meter, designed to assess the signal strength on the S-scale, respectively. All industrially produced transceivers are equipped with such a device. The scale of this device is non-linear, and the division value of its scale corresponds to a signal change of 6 dB. Thus, 1 point corresponds to 6 dB. The readings of the S-meter of any transceiver cannot be considered as absolutely accurate and, sometimes, even as approximate (we must not forget that on KB the level of the signal coming from the air CANNOT be compared at all with the one that came EARLIER due to the random nature of its path from the emitter to the receiver, even more difficult do this in SSB mode, since the signal amplitude changes due to changes in the voice level of the operator). These indications are suitable only for qualitative analysis of the degree of increase in the radiated power of the transmitting device. Now let's do some practice. Let's try to gradually increase the output power of the transmitter and observe how the S-meter readings change on the receiver of your correspondent and build a graph that reflects the cost of purchasing the appropriate amplifier. It is known that to increase the signal strength on the receiving side by 3 dB, it is necessary to increase the power of the amplifier of the transmitting station TWICE! Note that 3 dB corresponds to only half of one division of the S-meter scale, i.e. exactly half a point! Accordingly, to increase the signal strength on the receiving side by only one point on the S-meter scale, it is necessary to increase the transmitter power by FOUR times! Using such simple arithmetic, you can calculate the degree of increase in the output signal power of your correspondent based on the S-meter readings. On fig. Figure 1 shows three scales of an S-meter with readings corresponding to different powers of the correspondent's amplifier, illustrating this rule.
Thus, using a 1 kW amplifier instead of a 100 watt amplifier will cause an increase in the signal at your correspondent's receiver by about 10 dB (1.5 S-meter points), which is certainly a very noticeable event for the operator, but becomes even more noticeable when you understand that you have to pay about $ 1500 for this pleasure. That is how much a kilowatt amplifier of low quality costs. Buying an amplifier with a power of 1,5 kW (only 500 watts more powerful!) will already cost about $ 2500 (examples are given below), and on the S-meter you will see an increase in readings of 0.5 points. Here we are talking about the average cost of industrial KB amplifiers for amateur purposes, excluding crafts of domestic Kulibins and devices of the Ministry of Defense. An interesting conclusion: in this case, the difference between 5-6 and 5-8 will cost about $2500. However, the costs of radio amateurs who have chosen this particular path to improve their achievements are not limited to the costs of an amplifier. For example: in cases where the amplifier does not have an output tunable circuit, it is necessary to use an antenna tuner. The cost of commercially available tuners designed for 300 watts of power averages $500. And, of course, do not forget about the payment for electricity. An amplifier with an output power of 500 watts draws approximately 1000 watts from the mains. This proportion is also maintained at other capacities. For example, the beloved by many GU-78 at 4 kW in the antenna consumes about 8 kW from the network. And industrial broadband transmitters such as "BRIG" (1 kW), "FLAME" (10 kW) and the like, operate with an efficiency of only about 30% - then consider for yourself. When calculating, also take into account the fact that this equipment is a source of interference to other operating electronic devices. First of all - of course, television. Power amplifiers create a lot, to put it mildly, of inconvenience for fans of endless television series, which, like it or not, has to be reckoned with. With many problems associated with TV interference, various kinds of filters will help to cope. They cost money too. (Most recently, the Saratov company REMO mastered the production of some of them. Cheaper and better than imported ones ...) But, if the station is located in a rural area, then the lack of electricity will generally not allow even a long "a-a-a-a-a-le, one, two, three ..." to be made. In wooden rural houses and houses of "new Russians" one of the most important problems is fire safety. Fire extinguishers and the quality of wiring will be a constant headache. As a result, a considerable amount will run up. These are just the main aspects associated with using a powerful amplifier. And now let's take a closer look at another opportunity to improve the quality of communication: the use of an efficient antenna system. What you need to pay attention to in this case: first. It must be understood that: amplifiers only amplify the transmitter signal and, unlike antennas, do nothing to improve reception. Second. An extremely important property of an antenna is the ability to reduce the level of an interfering signal by exploiting its directional properties. By rotating the antenna, it is possible to achieve its optimal direction, corresponding to the highest quality signal reception, i.e. to improve the signal-to-noise ratio is the most important parameter in radio communication. The cost of an antenna providing a similar increase in the transmission signal level will be an order of magnitude less than the cost of a powerful amplifier. As already mentioned, increasing the power of the output amplifier by 6 dB (only 1 point on your correspondent's S-meter), i.e. FOUR times from about 100 W (standard transceiver power), costs: QRO HF-1000 (600 W) - $2690, Ameritron AL-80 V (850 W PEP) - $1350, Ameritron 811 V (600 W PEP) - $1050, Command Technologies HF-1250 (800 W) -$3250 (prices of Moscow companies are given). Specifically, 400-watt amplifiers were not found during the preparation of this material. It is interesting that the same increase (about 6 dB) in relation to the "long wire" of 84 meters, which is so popular among the people, has, for example, a conventional 4-element Yagi antenna or similar squares. And the use of more serious antennas provides even more gain, respectively. The cost of such antennas of domestic manufacturers is approximately from $ 100 to $ 400, depending on the range and degree of complexity of the antenna itself. We give very average prices, but even they speak eloquently for themselves. In addition, it must be borne in mind that a horizontally polarized antenna located above the ground has a gain of about 5-6 dB more than in free space (the exact value depends on the parameters of the ground). This factor must be taken into account when considering the efficiency of amplifiers and antennas. An increase in power from 1 kW to 4 kW (only 1 point on the S-meter again!) Will cost you $ 4-9 thousand: (QRO 3 KDX (2.8 kW), Henry 3 k ULTRA (ZkW), HF-2500E (2.5 kW)). A visual illustration of this is shown in fig. 2.
On the horizontal axis are the gain values of antennas located at a height of 22 meters above the real earth, expressed in dBi (for details on the gain, see page 4 of the catalog "BREEZE Winter 2001"). The values of the signal power that the antenna radiates are also plotted here, provided that the output power of the transmitter (transceiver) is 100 watts. In this case, this value is taken as the origin of coordinates. Gain and power are plotted on the same axis so that you can visualize the difference in signal amplification costs between amplifiers and antennas. The vertical axis is marked with the price that you have to pay for everything that is plotted on the horizontal. The graphs show data for 7, 14, 21, and 28 MHz antennas and a stack of two 14 MHz antennas. Thus, the graphs show what is the average Moscow price for the amplification received by certain antennas today. For example, the figure shows that a 14 MHz antenna with a gain of 16 dBi (5 YAGI elements) can be purchased for $750. Dots mark power amplifiers, which can be purchased today in Moscow companies. At the same time, the amplifiers are in a more favorable position with respect to the antennas, since the values of the power radiated into the air correspond to the operation of the amplifier on a half-wave dipole located at a height of 22 m. Take, for example, the ALPHA-87 A amplifier. At 100 watts at the input its output power is 1.5 kW, which corresponds to a gain of about 12 dB (15 times). If this amplifier were connected to an isotropic radiator, then we would plot it on our drawing on the vertical axis corresponding to a value of 12 dB. However, in our case, all amplifiers are driven by a half-wave dipole, so we need to add 2.15 dB (the difference in gain between the isotropic radiator and the dipole) and about 5 dB of ground effect. Total - almost 19 dB, which is shown in the figure. If a signal with a power of 100 watts is amplified by 19 dB, almost 8000 watts will be obtained. The same gain of 19 dBi (i.e. relative to an isotropic radiator) has a stack of only two antennas. It is significant that the price for the same amplification differs by almost 6 times! Even more revealing is the cost of the same gain gain for both amplifiers and antennas. Recall that a 3 dB increase in power (for example, from QRO-1000 to QRO-2500) will cost almost $ 2000, while the same 3 dB increase for large 7 MHz antennas will cost only $ 300-400. The figure does not show more powerful industrially produced amplifiers, since their price exceeds the values shown on the vertical axis and for this reason are available to units of domestic radio amateurs, so their appearance in Russia can be considered an exception. At the same time, do not be embarrassed by the fact that we are comparing single-band antennas with amplifiers operating on all bands, because if you have an antenna for only one band, then when buying an amplifier, you will be able to "amplify" all the rest bands you can't work on. The graph shows how much you can save by installing the appropriate antenna, while providing the same result on your correspondent's S-meter. Among other things, you have the opportunity to smoothly improve the performance of the antenna system by creating antenna stacks. Properly combining only two antennas into a stack, you can immediately improve reception (at best) twice, i.e. by 3 dB. In practice, everything turns out to be much more mysterious: by switching mutually the stack antennas and their power phases in various combinations (tiny devices do it now!) You can change the directivity pattern in the vertical plane of the entire antenna system, choosing the most suitable option at the moment. In our country, there are very few such antennas on HF, and there were few VHF players using such antennas, and it is becoming less and less. But in the world, the advantages of such an antenna system design have been known for a long time. What, for example, is the OH8OS stack, consisting of 6 antennas of 6 elements for a range of 20 meters (three floors of 2), on a mast 60 meters high and weighing 1.5 tons, which has a gain of about 25 dBi! In other words, this is equivalent to connecting a 100 kilowatt amplifier to a 30-watt transceiver! Or the W5UN antenna - the main "lunar" of the planet. Its design consists of 32 17-element antennas. The beam width in the E-plane is only 3.7°, and the gain is 32 dBi (1585 times the power)! Such a design rotates with two trucks, and it takes about 7 minutes to complete a full turn! Structures KS1XX, NCOP, W3LPL, W6KPC are fantastic structures! Of course, these mind-blowing antenna designs are inaccessible to most ordinary radio amateurs, however, simpler designs, consisting of 2 floors of modern multi-band antennas, are within the power of many. It is important to take into account that with an increase in the power of the output amplifier, its price increases exponentially, and the improvement of the antenna parameters (even taking into account the cost of the mast-reducer set) is given by much less effort and cost. Thus, the modernization of the antenna system is the most optimal way to increase the efficiency of the entire radio system, which allows not only to significantly improve the quality of radio communication, but also to minimize material costs. Also, improving the parameters of the antenna allows you to get rid of all the shortcomings described above, associated with the use of a powerful linear high-frequency signal amplifier. In our opinion, it is possible to designate 5 conditional categories of equipping amateur stations, where the transition to each subsequent, while maintaining previous achievements, allows you to feel a real qualitative leap in the results of work. First the initial is determined by the following set: - 100 watts and a long wire or multi-band whip antenna. The second: Use an amplifier with an output power of about 1 kW. The third: Install a rotatable directional antenna. The fourth: increase output power up to 3-4 kW. And the last one Fifth: Install antenna stacks. At this stage, you can relax, and until retirement (or during it!) Carelessly work on the air. Your success is guaranteed! The final decision on how to improve the efficiency of your plant is always yours. Important information: on the territory of Russia, in licenses of the first (highest!) category for KB (excluding 160 m), an output power of 200 watts is allowed! We recommend that the money earmarked for the second and fourth categories be directed directly to the fifth (Hi!). At the end of the article, we provide a useful table. After carefully studying it, one can draw interesting conclusions, such as: how many times (approximately) did your correspondent increase the output power of his RA when your S-meter showed a difference of 4 points (4 points is 24 dB or 250 times in power .. .), although he assures you that he has a ZhGU-50. Or how many times your signal will be "amplified" when you connect an antenna with a gain of 5 dBd instead of a "long wire" (5 dB = 3.1 times in power).
Authors: A. Dubinin (RZ3GE), A. Kalashnikov (RW3AMC); Publication: krasnodar.online.ru/hamradio
A New Way to Control and Manipulate Optical Signals
05.05.2024 Primium Seneca keyboard
05.05.2024 The world's tallest astronomical observatory opened
04.05.2024
▪ Summer fruits all year round ▪ Looking at the sick makes us healthier
▪ section of the site Power supply. Article selection ▪ article by Lope de Vega. Famous aphorisms ▪ blue article. Legends, cultivation, methods of application
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page