Antenna cans with their own hands

Introduced readers into the course of the question of designing half-wave vibrators, the topic is so extensive, at times new aspects will appear. The show, so beloved by the audience, which discusses how the antenna is assembled from cans with its own hands, is a new variation that excites the old theme. The structure formed by two tins arranged in a row on a stick forms a dipole - the first active antenna made by mankind. We will discuss the aspects of design, it will be useful for readers to learn: not only beer cans are good for the house, coffee and other tins will help. Readers who have seized the idea, can immediately go to study the graphs below, the rest will be interested in reading the theory.

Antenna Shortening Ratio

The shortening coefficient is commonly understood as a number indicating how many times the line wavelength is shorter than in free space. However, today we touch on another area. It has long been noted: the half-wave vibrator is equipped with ideal characteristics only with a minimum wire thickness( we drop the antenna suspension height).In reality, the wire is provided with finite dimensions that change characteristics. Concerns the frequency. Remember, the dimensions of a half-wave vibrator are determined by the wavelength.

When deviating from resonance, the reception will begin to fall, in practice they try to avoid the effect. With increasing diameter of the vibrator rod, the frequency goes up. Means: should be slightly shortened shoulders for accurate contact with the channel. To give the process a kind of scientific, introduced the term coefficient of shortening. The antenna shortening factor shows how much a percentage of the half-wave vibrator will need to be shortened to impart optimal properties to the system.

The graphic shows: the antenna shortening factor depends on the ratio of the wavelength to the doubled diameter of the wire from which the half-wave vibrator is made. Invented a different form of graphics, the meaning remains the same. For calculation it is more convenient from the point of view of minimization of calculations. Given the frequency of 100 MHz, the diameter of the copper tube, which served as the material, is 25 mm. We find the desired length of the half-wave vibrator using the formula.

Determine the wavelength: 299792458/100000000 = 2.998 m. We find the shortening coefficient using the graph, dividing 2.998 by 0.025( wire thickness), it turns out 120. The figure shows: K = 0.482.We conclude: the total length of a half-wave vibrator will be 1.445 meters. Immediately make a reservation, the calculated schedule strongly differs from the one below( theoretically assumed to be identical).In the second case, the length is smaller, the antenna is shorter than shortened to shorten. The fact speaks in favor of the last schedule: recommends a forum of radio amateurs, people gathered with a practical aim, therefore, you can trust. In any case, it is worth trying both.

How to determine the antenna shortening factor for beer cans

We hope, of course: we will assemble a half-wave vibrator from the cans only for that wavelength, which is approximately equal to the four can lengths. The design of the vibrator implies: both shoulders are equal, you should not try to take a tin of different drinks. High jars with low can not be the shoulders of one antenna. The distance at the break is typically 10–20 mm. Now you need to get a ruler, you can say which frequency is suitable for a regular beer can.

The necessary was found in an official document called GOST R 51756-2001 - Deep-drawn aluminum cans with easily opened lids. Technical conditions. Sizes are normalized, preliminary calculations will spend at home. The standard introduces four sizes of beer cans, indicated by the table. For the convenience of readers, the information given above( first figure).Anyone will find the standard text on the Internet.

We offer readers to do. .. There is a graph of the coefficients of the relative shortening of the half-wave vibrator, in the presence of the sizes of cans. Known distance between the shoulders, amounting to 10 - 20 mm. With information in hand, let's calculate the wavelength taken by the future homemade half-wave vibrator. The 0.5 liter can is provided with dimensions:

  1. Height 168 mm.
  2. Outer diameter 66.4 mm.

The dependence on the graph resembles a parabola, the logarithmic scale horizontally. Since there is no exact formula on the hands, it is proposed to determine the range, then, if possible, find the resonant frequency.

Double the height of the can, the gap between the shoulders is totally 350 mm. Half wave, not counting the shortening factor. It turns out a wavelength of 70 cm, the frequency of digital television. Let's find more precisely: 299792458 / 0.7 = 428.3 MHz. Now it becomes clear why some clever people use beer cans to catch television channels.

Calculate the shortening factor for the first( top) graphic, it turns out: λ / d = 0.7 / 0.0664 = 10.54.At the left of the scale, K = 0.4625.We find the frequency under which the half-wave vibrator is suitable by multiplying by a factor, only doubled.396 MHz. For comparison, the first multiplex of Moscow is broadcasting at 560 MHz. Banks take shorter. Approximately 560/396 = 1.41 times, gives the height of the tank 118 mm. Length according to the standard beer can 0.33 liters. According to our own calculations, it turns out: if you make an antenna out of cans with your own hands, the first multiplex of Moscow catches. Unknown involved in the selection of frequencies, but the figure( 560 MHz) makes you wonder.

Adjusting the antenna of beer cans to the desired channelThe main thing is that the two shoulders remain parallel, they should be horizontal. Attach - each in his own way much. Shovel handle, clothes hanger, curtain, any suitable item.

The question arises how to tune the antenna collected from beer cans. We see two factors that need to be agreed:

  1. Line impedances and antennas.
  2. Question balancing.

Digital television channels have chosen the UHF range, balancing has no decisive role, as on longer waves. As for the wave resistance, for a perfect half-wave vibrator, the figure oscillates in the range of 72-76 Ohm, it is consistent with a television cable. Allowed freedom in dealing with numbers, readers noticed: you can not multiply the length of the antenna by the selected factor, the figure will be less than that obtained graphically. Aspects mentioned, the error of engineering calculations( 30% is laid), makes it necessary to adjust the self-made antenna.

Easier to do, changing the distance between banks. Varies widely, it is logical to use. With an increase in the diameter of the wire( banks), the antenna bandwidth increases. For ratios of wavelength and wire diameter of 10,000, the range where the CWS can be adjusted within the required limits is 6.5%.With a ratio of 100, the parameter increases 2.5 times. Useful property for antennas. By the way, for this reason, literature considers half-wave vibrators, in which a plurality of shoulders form cylindrical surfaces on either side. By similar principles, fractal bicone antennas are implemented, discussed briefly in previous reviews.

Canned antenna mount with sealants. Silicone plumbing costs a penny, you will find in the hardware store. To prevent the antenna from breaking by the wind, firmly fasten the structure. Silicone fearlessly meet the rain, passes radio waves. Use modern technology, combining with proven designs. By the way, not only beer cans are suitable for the manufacture of the antenna. Metal cylinders come off.

From what we have said, remember, it’s really possible to make an antenna out of cans by yourself. And any capacity suits. It is possible to make pipes from cardboard, to glue over with aluminum foil, obtaining an acceptable result. Difference from traditional design in broadband, a number of difficulties with coordination. A wide field opens for experimenters: it is much easier to handle cardboard and foil. Homemade antenna from the cans will be an unusual interior decoration, if the colors are chosen correctly. To top it off, let's say: the YouTube clip is deprived of the simplest calculations, it is hard to get a good result by discarding the theory. Attempts to catch the First Channel lacked the bandwidth of the device. That is why the antenna from the cans assembled on the table worked poorly. Although. .. during the Olympic Games it turned out that the reception was unsure, perhaps this is the case.

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