Antenna or amplifier?
This material is useful for those who would like to spend the money to improve the quality of communication with maximum efficiency, it examines different ways of achieving so essential decibels and estimates of costs to obtain them.
Not all, but many hams will sooner or later face the problem of improving the quality of communication. Questions this raises a lot, but usually only two: buy powerful linear amplifier or improve the antenna system? Both can largely be classified as philosophical. Well, we will try to consider them in detail from the viewpoint of material cost and ergonomics, i.e. the improvement of consumer qualities of radio systems and, on the basis of these reflections we will try to give advice that some of you will even be able to try to exploit.
In recent years, the world has seen a steady trend towards a decrease of transmitter power, where such a possibility exists. This is due to the introduction of new directions of development of modern technology - energy saving-saving continuously depleting mineral reserves, which in turn, are used to produce electrical energy, and increasingly the rhetoric of "green" about the dangers of any radio emission. These facts, of course, are not determinative when choosing a method of improving the efficiency of communication for millions of hams worldwide. They (including us) always want more-more-more powerful, even if you have to wear lead gowns! Someone needs first DXCC, someone 9V WAZ, and so on to infinity! The accumulation of awards, praising ourselves for some is the goal of life is number 1! With age it becomes a habit, and there's no looking back.
The first thing that the radio operator comes to mind when you desire to stand out among the rest is to produce an unusually powerful amplifier. However, with a detailed consideration of the problem, the evidence indicates that the installation is too powerful linear amplifier to increase the level of emitted signal is not the best solution.. One of those facts is the ratio price/quality of the achieved results. Well, in our country, the problem of the price of pleasure remains in this matter, perhaps the main.
Before further consideration of the question let us digress for a brief introduction to some of the device: the so-called S - meter to assess the signal strength on the S-scale, respectively. This device is equipped with all industrial produced transceivers. The scale of this device is nonlinear, and the price of division of its scale corresponds to a change of signal 6 dB. Thus, a score of 1 corresponds to 6 dB. The S-meter of any of the transceiver cannot be regarded as completely accurate and, sometimes, even as a rough (we must not forget that on the LW signal level coming out of the ether do NOT compare with those who came EARLIER because of the random nature of its path from the emitter to the receiver, it's even more difficult in the SSB mode, because the signal amplitude changes due to changes in the level voice of the operator). These indications are suitable only for qualitative analysis of the degree of increase of the emitted power transmission device.
Now let's draw some practical lesson. Try to gradually increase the output power of the transmitter and observe how change the S-meter on the receiver of your correspondent and create the graph, which reflects the cost of the acquisition of the amplifier. It is known that to increase the signal strength on the receiving side 3 dB needs to increase the power amplifier of the transmitting station IN LWА TIMES! Note that 3 dB correspond to only half of one division of the scale S-meter, i.e. exactly half-points!
Accordingly, to increase the signal strength on the receiving side only one point on the scale S-meter it is necessary to increase the transmitter power is already FOUR times! Using such simple arithmetic we can calculate the magnification of an output signal of your correspondent on the basis of testimony S-meter. In Fig. 1 shows the three scale S-meter with readings corresponding to different power amplifier correspondent illustrating this rule.
Thus, the use of the amplifier 1 kW instead of 100-watt will cause an increase of the signal at the receiver of your correspondent about 10 dB (1.5 points on the S-meter), which, of course, is a very significant event for the operator, but becomes even more noticeable when you realize that to pay for this pleasure about 1500$. That is the cost of a kilowatt amplifier of low quality. Buy amplifier 1.5 kW (500 watts powerful!) would cost about $ 2500 to $ (examples below), and the S-meter you will see the readings increase by 0.5 points. We are talking here about average cost of industrial LW amplifiers for Amateur purposes, excluding crafts Patriotic Kulibin and devices of the Ministry of defence.
Interesting conclusion: in this case the difference between 5-6 and 5-8 will cost about 2500$. However, the costs of radio Amateurs who have chosen this way to improve their achievements, not limited to the cost of the amplifier. For example: in cases where the amplifier has a tunable output circuit, it is necessary to use an antenna tuner. The value produced by industry tuners, designed for 300 watts is around 500$. And, of course, do not forget about the electrical power. Amplifier, output power of 500 watts, consumes about 1000 watts from the network. Such proportion is retained in other capacities. For example, beloved by many GU-78, with 4 kW antenna powered for about 8 kW. And industrial, broadband transmitters type "BRIG" (1kW), "FLAME" (10 kW) and similar, work with an efficiency of only about 30% - then consider yourself. When calculations note also that this instrument is a source of noise other electronic devices. In the first place - of course, television. Amplifiers create a lot, to put it mildly inconvenience for fans of infinite series, which like it or not - has to be considered. With many of the problems associated with interference to the TV will help to make various kinds of filters. They also cost money. (Most recently, the release of some of them mastered the Saratov company REMO. Cheaper and better than the imported ones...)
But, if the station is in a rural location, the lack of electricity generally do not give even a long "Ah-Ah-Ah-Ah-Ah-Le, one, two, three...". In wooden rural houses and homes "new Russians" one major concern is fire safety. Fire extinguishers and the quality of the wiring will be a headache. Eventually will run across a considerable sum. This is only the basic aspects associated with the use of a power amplifier.
Now let us consider another possibility of improving the quality of communication: use effective antenna system. What you need to pay attention in this case:
First. You must understand that:
amplifiers amplify only the signal from the transmitter and, unlike antennas that do nothing to improve reception.
Second. A very important property of the antenna is the ability to reduce the level of interfering signal due to the use of its directional properties. Rotating the antenna, can achieve the optimal direction corresponding to the best quality signal reception, i.e., to improve the signal-to-noise ratio is the most important parameter in radio communications.
The cost of the antenna, providing increased signal level to the transfer, will be much less than the cost of the power amplifier. As already mentioned, increasing the power output of the amplifier 6 dB (only 1 point on the S-meter of your correspondent), i.e. FOUR times with approximately 100 watts (the power of a standard transceiver), is: QRO HF-1000 (600 W)-2690$, Ameritron AL-80 (850 watts PEP)-1350$, Ameritron 811 (600 watts PEP)-1050 $, Command Technologies HF-1250 (800 W)-3250$ (prices quoted Moscow companies). Specifically 400-watt amplifiers in the preparation of this material could not be found. Interestingly, the same increase (about 6 dB) in relation to so-popular "long wire" to 84 meters has, for example, a conventional 4-element Yagi antenna or similar squares. But a more serious antennas providing even greater amplification, respectively. The cost of such antennas domestic producers is approximately 100 to$ 400, depending on the range and complexity of the actual antenna. We provide very average pictures, but even they eloquently speak for themselves. In addition, you must keep in mind that the antenna with horizontal polarization 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 earth). This factor must be taken into account when considering the efficiency of amplifiers and antennas. The increase in power from 1 kW to 4 kW (again only 1 point on the S-meter!) will cost about 4-9 m $: (QRO 3 KDX (2.8 kW), Henry 3K ULTRA (Scvt), HF-2500 (2.5 kW)).
Visual illustration of this is shown in Fig. 2.
The horizontal axis is the gain of antennas located at a height of 22 meters above real ground expressed in dBi (for details, reinforcement see page 4 of "the BREEZE Winter 2001"). Here the plotted values of signal power emitted from the antenna is provided that the output power of the transmitter (transceiver) is 100 watts. Thus at the origin of coordinates adopted this value. The gain and power are plotted on the same axis, in order to demonstrate the difference in price signal amplification for amplifiers and antennas. On the vertical axis plotted the price you have to pay for everything that is plotted on the horizontal. In the form of graphs presents data for the antennas, ranges 7, 14, 21 and 28 MHz and a stack of two antennas of the 14 MHz band. Thus, the graphs show what is Moscow today, the average price for gain, get the or other antennas. For example, the figure shows that the antenna band 14 MHz with gain of 16 dBi (5 element YAGI), can be purchased for 750 $. Dots indicate power amplifiers that can be purchased today in the Moscow companies.
The amplifiers are in a more favorable, relative to the antenna position, since the values emitted on the air power correspond to the operation of the amplifier at half-wave dipole located at a height of 22 m. Take, for example, the amplifier ALPHA-87 A. At 100 watts input power output is 1.5 kW, which corresponds to a gain of about 12 dB (15 times) If this amplifier was connected to the isotropic radiator, we would put it on our drawing on the vertical axis corresponding to the value of 12 dB. However, in our case all amps operate on half-wave dipole, so we need to add 2.15 dB (the difference in gain between an isotropic radiator and a dipole) and an additive of about 5 dB caused by the earth's influence. A total of almost 19 dB, as shown in the figure. If the signal power of 100 W to strengthen 19 dB will be almost 8000 watts. The same gain 19 dBi (i.e., relative to an isotropic radiator) has a stack of two antennas. It is indicative that the price for the same gain varies almost 6 times! Even more revealing looks the same value of gain of gain for amplifiers and for Anen. Recall: increase power by 3 dB (for example, QRO-1000-QRO-2500) would cost almost 2000 $, while the same 3 dB rise for large antenna 7 MHz would cost 300-400$.
The figure does not show a more powerful amplifiers, manufactured, because their price exceeds the values shown on the vertical axis and for this reason only few local radio, so their appearance in Russia is an exception.
Thus do not be confused by the fact that we compare single-band antennas with amplifiers operating on all ranges, because if you have antenna only on one range, then buying an amp, you "load" will receive the opportunity to "enhance" and all the other bands, work on which will not.
The graphic shows how much money can I save by installing an appropriate antenna, while providing the same result on the S-meter of your correspondent.
In addition, you have an opportunity to gradually improve the performance of the antenna system, creating a stack of antennas. Intelligently combining a stack of only two antennas, it is possible to improve reception immediately (at best) twice, i.e. on 3 dB. In practice, everything goes much more enigmatic: mutually switching the antenna stack and phase their power in various combinations (now it is done by a tiny little machines!) you can modify the radiation pattern in the vertical plane of the entire antenna system, choosing the most suitable at the moment option. In our country such antennas for LW is extremely small, and УSW-earnest using such antennas were few, and becoming fewer and fewer. But in the world the advantages of this design of the antenna system have long been known. Take, for example, the stack OH8OS consisting of 6 antennas and 6 elements in the range of 20 meters (three floors for 2), on a mast height of 60 meters and a weight of 1.5 tons, which has increased about 25 dBi! In other words it is equivalent to connecting to a 100-watt transceiver 30 kilowatt amplifier!
Or antenna W5UN - main "honesty" of the planet. The design consists of 32 17 element antennas. The width of the lobe of the antenna in the plane E is only 3.7°, and the gain is 32 dBi (1585 times the power)! Rotates this design two trucks, and, to make a complete turn takes about 7 minutes!
Design XHH, NCOP, W3LPL, W6KPC - fabulous structures! Of course, these stunning designs of antennas of the reach of most ordinary radio, however, a more simple design, consisting of 2 floors of a modern multi-band antennas under the force of many. It is important to note that while increasing the power output of the amplifier increases in its price occurs in a geometric progression, and improvement of parameters of antennas (even considering the cost of a set of mast-gear box) is significantly less power and costs.
Thus modernization of the antenna system is the best way to increase the efficiency of the entire radio system that allows not only to significantly improve the communication quality, but also to minimize material costs. Also the improvements of the antenna parameters allows to get rid of all of the deficiencies described above related to the use of powerful linear high-frequency signal amplifier.
In our opinion you can identify the 5 broad categories of equipment Amateur station where the transition to each subsequent, while maintaining previous achievements, allows you to experience the real qualitative leap in performance.
The first primary is determined by the following set: - 100 watts and a long wire or multi-band whip antenna.
Second: the use of the amplifier with an output of about 1 kW.
Third: install a rotating directional antenna.
Fourth: increase power output up to 3-4 kW. And last,
Fifth: set the stack of antennas. At this stage you can relax, until retirement (or during it!) carefree to work in television. Success is guaranteed!
The final decision on the choice of a method of increasing the efficiency of your station is always yours.
Important information: on the territory of Russia in the licenses first (highest!) categories for LW (except 160 meters) allowed output power of 200 watts!
We recommend that the money destined for the second and fourth categories, to send at once in the fifth (Hi!).
In conclusion, we present a useful table. Having carefully studied it, it is possible to draw interesting conclusions, such as: how many times (approximately) your correspondent has increased the power output of their RA when your S-meter showed a difference of 4 points (4 points - 24 dB or 250 times power...), although he assures you that he Shgu-50. Or how many times the "skyrocket" your signal when you connect the antenna with gain 5 dBd is a "long wire" (5 dB=3.1 times the power).
Authors: A. Dubinin (RZ3GE), A. Kalashnikov (RW3AMC); Publication: krasnodar.online.ru/hamradio, www.cxem.net