20 Jun 2014

Antenna for 432 MHz band with 21 dB gain

Antenna Backscatter length 4L. Antenna is shown in Figure. The antenna has a gain of 21.4 dB
with respect to increased half-wave dipole. The excitation system consists of a vibrator and a reflector nine directors. Reflector antenna configured as a disc whose diameter is equal to one wavelength. The vibrator has a length KL / 2. The first director is spaced a distance from the vibrator W-D1 = 0,2 L, each next - at a distance of 0,4 L from the previous one. The lengths of all Directors are equal (length director depends on its thickness). Full length of the excitation system is 4L. Large M reflector antenna has a diameter D, = 4L. In front of him at a distance of 0.25L. placed another ring-shaped reflector, the external diameter of which is 6L, and the internal - 4L. Studies have shown that this antenna has a gain of 8 dB greater than the antenna Uda-Yagi length 8L. Height w reflector ring is usually 0,25 L. Research has shown that an additional effect on the height of the antenna gain. The second figure shows the dependence of gain for one value of the diameter D = 2,35 L. Additional strengthening is added to strengthen that implements regular antenna is Backscatter flat reflector. An antenna with a large gain value for the 432 MHz band encounters certain difficulties, especially associated with the manufacture of a reflector of a sufficiently large diameter, since in this case it is necessary to ensure the necessary rigidity of the reflector and the carrying beam. Advantages of this antenna: high gain, power and simplicity of the relatively small size of the antenna criticality.

antenna fo 432 mhz

17 Jun 2014

Balancing and matching of the antenna and power lines using two identical segments wire line

Previously discussed the coordination and balancing of the antenna and the power line using a ferrite ring. But alignment and balancing can be done using two-wire line segments having their own impedance Z1 (in the figure) of the same length equal to a quarter wavelength (L / 4) and connected in parallel to each other at the connection point feeder BB. At the points AA intervals one pair of wires are connected with each other and another pair of wires connected to the segments of the antenna. This scheme allows not only to symmetrize but also to match the antenna. Length of the two segments should be strictly the same and should be designed with the condition of shortening of K equal to 0.66 for coaxial cables. Also keep in mind that the points BB is full of tension and convergence wire line baluns can change their input resistance.
balancing and matching of the antenna and the power supply line

8 May 2014

antenna theory

An antenna is a device for transmitting electromagnetic energy from the supply line to free space and vice versa. Antenna dares active element - the vibrator , an antenna may also contain passive components (one or more). To the active element of the antenna connected power line . When the alternating voltage supply line around the active element ( vibrator ) , a magnetic field. Passive antenna elements are needed for the formation of the magnetic field of a certain field of the structure and formation of the directional properties , impedance matching system " space - antenna power line .
The antennas can be categorized into three groups : linear antenna aperture antennas, surface-wave .
Linear antenna - is a regular cable or wiring system . Radiation is determined by the spread of linear antenna currents on its wires and their mutual orientation. This group includes the rhombic antenna vibrator . These antennas are often used in the square -wave range .
The next type of antennas is aperture antenna ( reflector antennas , parabolic ), these antennas are characterized by the presence of surface ( aperture ) , which is a transformation of energy propagating in the supply line to the radiation energy . Typically, the size of the aperture is significantly larger than the wavelength . Radiation of this antenna is determined by the structure of the electromagnetic field on the aperture .
And another group is a surface wave antenna . The emission of these antennas plays the role of a surface wave . It extends along the antenna part in the process of radiation. Antenna radiation is determined by the way of connecting to the power supply line and the condition of wave propagation along the antenna . Representative of this group is the antenna Uda - Yagi .
The antenna system is simply a collection of separate antennas. Application of the antenna system increases the possibility of the formation of the desired patterns . The antenna system provides a higher gain compared with a single antenna for enhancement (in level signal).

12 Apr 2014

Car antenna for the 144-146 MHz

In one of the amateur radio magazines Russia was published scheme homemade car radio for range 144-146 MHz antenna also for this station . Well, since my blog about the antenna I decided to show you this antenna . And so I had not considered a thief to start write in what magazine was published this scheme automotive radios and antennas respectively for her magazine is " radio ham " 1992 , № 5 . (In Russian) . As can be seen quite unpretentious dish , but its size makes it clear that it is much more effective than in the smaller antenna . This car antenna for the 144-146 MHz range includes : vibrator coil , a magnet , a pair of insulators , it all (except the vibrator ) is placed in the body. The antenna is connected to the transmitter via a coaxial cable with an impedance of 50 ohms. The coil is wound silver-plated wire , wire diameter 3 mm, 4 coils has a diameter of 30 mm and stretched to a length of 40 mm. In the upper part of the housing is an insulator that is inserted into the vibrator antenna coil connected thereto , it is also inserted into the lower outlet in the insulator and connected to the center conductor of the coaxial cable. Below is an insulator under the magnet , whereby car antenna mounted on the roof of your car . Braid is soldered to the body of the antenna. Tuned antenna with a coil , compressed or decompressed its coils antenna configured directly on the roof of the car in the place where it will be located permanently in this place need to change the antenna tuning in section 144-146 MHz . In the presence of the auto antenna tuning devices easier and more tochnoy.Vot and all descriptions . Successful if you travel far and qso.73! yet !

This car antenna for the 144-146 MHz range includes : vibrator coil , a magnet , a pair of insulators , it all (except the vibrator ) is placed in the body

15 Mar 2014

Using shortwave antenna coils and capacitors, as switching elements

Previously considered for shortwave antenna in which as of extension elements used inductors and capacitors (w3dzz), on this page on your blog suggest considering another shortwave antenna published in the Soviet journal Radio hobbyist and part-time engineer I.Adamkovskim (UA3APM) of Moscow region, the article came out in 1969.
The figure shows that the total antenna length of about 40 meters, shortwave antenna operates in the 80,40,20,14,10 meters . Input impedance of 600 ohms , depth of about 20 meters from the surface . As the supply line used ribbon cable 300 ohm. This cable is made of transformer converts the input impedance of the short-wave antenna (600 ohm) to 300 ohms resistance . Why do I need this! ? All banal just - in those years in the USSR was not ready supply line impedance 600 ohms , but there were 300 ohms. If you decide to make this dish one to one , then overcame drawing in which all dimensions are in meters and millimeters. Coil wound carcass without winding diameter of 30 millimeters , 43 millimeters winding length . These wire coils - Copper 1.2 millimeter its diameter . ( Having instrumentation I think will be easy to set up ) . Capacitors used in this shortwave antenna pifarad have a value of 300 with a working voltage of at least 1 kV . After setting up the short- circuit antenna to be sealed .

ps: capacitors and coils in the shortwave antenna play the role of automatic switches.

shortwave antenna

1 Feb 2014

Two wire antennas range of 1.9 MHz

These two simple wire antennas are designed to operate in the 1.9 MHz amateur band . They are connected to a coaxial cable with a characteristic impedance of 50 or 75 ohms. Total length of the wire antenna should be: for the first figure of 38 meters, the second slightly longer than 43 meters . Of both figures show that the wire antenna for 1.9 MHz band as it split into two sections - the antenna itself and reduced to connect the matching device and coaxial cable. Here it should be noted that the ratio of these areas antenna wires can be anything, the main thing here is the total length of the antenna wire and the length of these sections can be arbitrary. Inductance for the first wire antenna is 13 micro Henry , she performed on a frame of 50 mm diameter , has 20 turns of copper wire with a diameter of 0.8-1.0 mm. Winding length of 50 mm. In this design, the wire antenna for 1.9 MHz is much more difficult to make (or find) the variable capacitor ( in terms of its dielectric strength ) , to transmit power to 10 watts , you can use a regular capacitor . Setting a first embodiment of a wire antenna for a range of 1.9 MHz start with the settings in the resonance of the capacitor at the operating frequency , on the selection of the number of coil turns achieve minimum SWR. Antenna in the second picture has an active component of the input resistance of about 50 ohms. Please compensate capacitor C reactive component of the input resistance (it has an inductive character ) , and then pick the length of the antenna SWR , each time adjusting the capacitor C. Because of the high input impedance of this antenna is more efficient than the first wire antenna pattern but the latter is easier to setting , as it requires careful selection of the overall length of the antenna. For these two wire antennas for a range of 1.9 MHz required good " grounding system " , in the simplest case, a system of " earth " should be supplemented by at least one counterweight to the maximum possible length ( but not less than 5 m) .
wire antennas range of 1.9 MHz

wire antennas range of 1.9 MHz

18 Jan 2014

Anti noise wire antenna for MW and LW bands

On this page of their site, I want to tell you that I found this description of the Russian Internet wire antenna , which I was very interested . This wire antenna for observers (SWL). What I'm interested in this dish: the first - is its simplicity , the second - that I have the opportunity to set it up , and the third - this antenna anti noise , well, that this fourth antenna operates in the long and medium waves . About the last ( fourth ) will say that I particularly recently started exactly like the medium wave and long wave bands and radio stations operating amplitude modulation. Real romance for radio amateur observer why I ceased to please ssb I do not know , but it seems just tired of these unnatural narrowband signals. And maybe that's why I decided to turn its attention to the low-frequency ranges . Of course these bands in Russia is very much noise but may be due to its two digital radio WinRadio and SDR-IQ that will work with this wire antenna I get to grips with this problem. This summer I will try to install this antenna . And so I will not steal someone else's article and pictures here and just giving this < link > to it . And to describe briefly what there are articles and pictures I think you will understand even though they are in Russian, everything is clear . For a full translation of an article on this wire antenna , you can use < translator google>. It states that the use of an antenna that receives the magnetic component of the electromagnetic field to reduce the noise level is almost 100 times ! Wire antenna in question in the article is very close to the ground , you can even put it in general . Admission to this antenna is carried out with the direction perpendicular to the plane of the frame antenna , ie reception of the station most distant from the point of finding antenna (similar vertical emitter ) . Due to the fact that the wire antenna is very low to the ground resonance it is missing, it is obtained as a shunt to ground. Dimensions of this antenna is to be performed for the highest frequency band ( wire antenna dimensions for a range of communication and there are doors ) . There's also said that raising it too high , too, do not need , it will lead to a drop in antenna gain . The antenna connected to two coaxial cables , and there are drawings of how to connect these cables to the symmetric and symmetric receiver input . The author writes that he took the radio communication range and doors to all on a very short antenna , but with a short wire antenna becomes difficult to receive distant stations . Generally, if it is not clear that you will be from the translation please contact me by e-mail envelope is below , we will try together to understand this wire antenna for SWL.

(here the translation of the text in the picture)

11 Jan 2014

Wire loop antenna for a range of 1.9 MHz

Compared with the antenna for the transmitter antenna to the receiver is not too difficult , even for a band as 1.9 MHz . Typically, such wire antenna is a frame that consists of one or several coils . Wire loop antennas have two distinct minimum when the signal directed perpendicular to its plane . Suppression of radio signals and interference are the side of the loop antenna can reach about 30 dB ( five points on the scale S!). An embodiment of the wire loop antenna shown in Fig . The antenna has three turns ( a square with sides 1.5 meters ) , forming a frame, and one round of communication . Any wire diameter , the usual equipment wire. The frame is placed in the electrostatic shield , open at the top. The screen can be made of braided coaxial cable , fixed to the frame cross member of the dielectric. Framed wire antenna is tuned to the operating frequency of the capacitor C1 , which must be protected moisture. To frame the receiver is connected via coaxial cable with a characteristic impedance of 50 ohms.
Wire loop antenna for a range of 1.9 MHz

4 Jan 2014

wire antenna for a range of 1.9 MHz

Range of 1.9 MHz or 160 meters when it was very popular among novice hams former USSR. Today, apart from interference on it you will hear nothing . One of the problems of falling interest to a range of 1.9 MHz was of course the complexity of the antenna . To work effectively in this range, the length of the antenna wire should be 40 meters, depth of the antenna should be almost the same at a lower altitude aerial suspension ceases to work effectively in medium and long routes . The most effective range of the antennas to 1.9 MHz (160 meters) are the dipole and loop antenna , the length of which is commensurate to the wavelength. But to establish a dipole wire antenna type is also problematic , such an antenna length should be about 80 meters. In order to reduce the physical length of the antenna can be applied lengthening doghouse as in antenna w3dzz, the antenna can be used to work in a range of 1.9 MHz as shown in the figure below . Unlike in this embodiment w3dzz no capacitors and it can also perform as the " inverter V". The length of the wire antenna is reduced in two (in comparison with the dipole ) , to reduce the loss extending spools must have their own small losses and high Q (of order 150) are also protected from moisture. Connect the antenna 50 ohm coaxial cable , when the size of said inductance coils L1 and L2 should be 70 mH. Setting wire antenna produce change in the length of external conductors ( Figure they have a length of 14 meters) . Having measuring instruments MFJ or other firm I think setting this wire antenna will not cause difficulties . Antennas operate as " inverter V" on the mast height of 15 meters.
wire antenna for a range of 1.9 MHz

30 Dec 2013

Calculating vibrator logoperiodic antenna

Broadband log-periodic antenna aimed work without rebuilding ten - twenty fold and the broader range of wavelengths . Log-periodic antenna can be used as antennas connected to the HF and VHF bands , as well as for receiving TV channels . The figure shows the log-periodic antenna, it consists of a series of vibrators connected with consistent variable phase to two-wire line . Dimensions vibrators and the distance between them decreases exponentially towards the connection point of the feeder or coaxial cable. Behind the longest dipole antenna located logoperiodic jumper that improves coordination with feeder . The distance between the jumper and the vibrator is chosen experimentally in the antenna settings. Feeder (coaxial cable with an impedance of 50-75 ohms) goes inside one of the tubes of a double line (no matter through what) . Parameters and log-periodic antennas determine the size structure of the period "t", equal to the ratio of the length to the length of follow- vibrator and the previous angle "a" at the apex of the triangle , which are inscribed vibrators . The closer the structure period "t" by one and the smaller the angle "a", the higher the gain the log-periodic antenna. But this increases the size of the antenna , often choose "t" = 0.8-0.9 and the angle "a" = 30-45 degrees. At each frequency waves in the operating range of the work involved those vibrators, resonant frequencies that are closer to this frequency (3-4 vibrator ) . Strengthening logoperiodic antenna are obtained with approximately 5-7 dB. In order to calculate the size of the log-periodic antenna vibrators need to know the length of the extreme waves Lmax and Lmin operating range. To determine the length of the longest start vibrator l1 it should be 0.55Lmax, built on an isosceles triangle with an angle "a" at the top equal to 30-45 degrees, the base of the triangle will vibrator l1. Second vibrator logoperiodic antenna located at a distance d1 = (0.15-0.18) Lmax from the first. The dimensions of the vibrator are uniquely determined size of the triangle. Likewise, the following dimensions are determined antenna dipoles . Distance d2 = d1 * t, d3 = d1 * t and so on. This arrangement continues until the next length is not equal to oscillator 0.45Lmin, this vibrator will last
Calculating vibratorv logoperiodic antenna

21 Dec 2013

VHF wire antenna for field use

As a VHF antenna for field use, you can use the wire antenna for the range of 144-146 MHz. This antenna wire has a sufficiently large size of its length 16 meters 8L is the wavelength. A feature of this wire antenna designed as a radio amateur from Germany is that it is made on insulating cord. All elements of VHF antenna made ​​of wire with a diameter of 3 mm. Part of Directors of the wire are the same size equal to 915 mm (antenna DJ4OB in the figure below). The vibrator is made of a wire or tubing of different diameters, the material from which the tubes are made to be the same. The upper antenna element DJ4OB vibrator has a diameter of 8 mm and a bottom diameter of 2 mm. Input impedance of wire antennas for VHF band 144-146 MHz is about 240 ohms. The antenna gain of about 15 dB. Since the antenna is a rigid base (yoke), it can easily be rolled up and thereby transported to the place of deployment. This wire antenna can operate only in one direction for obvious reasons.
VHF wire antenna dj4ob for field use

small active antenna

This small active antenna published in the German magazine Funkamateur, 1999, № 7 is designed for receivers operating in the range from 6 to 30 MHz, provides radio stations in several radio and amateur radio bands . Active antenna has an input impedance of 50 ohms and is a frame , the frame is set to the operating frequency of a variable capacitor (C1). Frame active antenna is connected to the amplifier using bipolar transistors and field . FETs provide high input impedance and low input capacitance . This allows you to completely connect the frame to the amplifier and get a high transmission factor devices , as well as a large block without switching bandwidth. The amplifier of an active antenna used high field and bipolar transistors with a cut frequency of about 5 GHz. If the transformer T1 is made correctly you can get the bandwidth of the amplifier 1 ... 100 MHz. Transfer coefficient with its input to the load 50 ohm - about 1. Inductor L1 circuit FET drain VT1 and VT3 need to increase the input impedance of the amplifier at the high operating frequency portion of an active antenna . Chain of diodes VD1-VD6 need for voltage stabilization ( 4volta ) on the bases of bipolar transistors . Application Zener is not justified , since they generate a high-frequency noise stabilization mode can negate all the advantages of the amplifier. Current consumption of less than 3 mA , so it can be powered by compact battery 9 V . Transformer T1 is made on the annular yoke size K13h7 , 9h6 , 4 mm of ferrite with an initial permeability of 800 . I contain three winding coil and the winding II and III - 20 turns. Wire - Litz wire . Frame active antenna is formed from copper tubing with a diameter of 16 mm and has a ring shape with a slit 1m diameter , which is placed in the variable capacitor C1. Conclusions from the stator is connected to the frame and the rotor or not connected to anything . This minimizes the impact of hands when setting the operating frequency of the antenna . Frame mounted vertically on the insulating base on which you installed the capacitor C1 and the other elements of the amplifier , the battery power to the switch . The upper part of the frame is supported by a vertical bar insulation . Along it to the amplifier goes wire removal from the frame (just from its center ) . Q-factor framework for the 6 MHz - about 1000 . This provides a high transmission ratio device as a whole , and good filtering interfering radio signals . If the interfering station is receiving a strong signal and operates at a frequency close to the resonant frequency of the active antenna amplifier nonlinear effects manifest . Since the frame has a spatial selection , then these problems can be eliminated partially optimal orientation of the frame.

small active antenna

7 Dec 2013

wire antenna w3dzz

Amateur radio is very popular among the wire antenna w3dzz, description and operation of this wire antenna often occurs in amateur literature . This popular wire antenna w3dzz is that with small linear dimensions , it can work in several amateur bands . The figure shows a further embodiment of the antenna w3dzz. This version of the wire antenna is designed to work in the amateur bands 1.9 , 3.6, 7, 28 MHz . Total length of the antenna about 67 meters. To connect to the transmitter output w3dzz can use a coaxial cable with a characteristic impedance of 50 or 75 ohms. Coils are wound on a frame 25mm in diameter of a copper conductor with a dielectric diameter of 1 mm, number of revolutions 38. Capacity (c1 and c2) capacitors antenna is 470 pF (four series-connected capacitor with a total capacity of 470 pF ) , the voltage at which shall be calculated these capacitors should be at least 500 volts. These capacitors are located inside the mandrels and are filled with sealant. Frequency tuning L1C1 and L2C2 is 3580 kHz . VSWR w3dzz at frequencies from 1840 to 3580 not more than 1.5, 7.1 and 7 ... 28.2 ... 28.7 - 2.
wire antenna w3dzz

16 Nov 2013

The magnetic loop antenna wire portable CB radio

The figure below shows the magnetic loop antenna for cb band , made of copper wire with a diameter of 2 mm. The antenna has an impedance - 50 ... 75 ohms and a low reactivity. The bandwidth of the magnetic loop antenna - 600 kHz. Air condenser is mounted on a prison setting . The antenna is insensitive to the effects of human and balances. This antenna radiates in the main magnetic component of the electromagnetic wave , it can not compare in terms of field strength with a whip antenna , because the whip antenna emits electrical component of the electromagnetic wave , and measurements for the probe should be carried out on the electrical component and the frame - by the magnetic component . Were compared between the standard helical antenna cb radio and wire magnetic loop antenna was tested in the communication range . It was found that under equal distance communication using magnetic antenna was not less than 1.5 times the open area, and 2 ... 3 times larger in urban environments . In this case, a significant effect of the magnetic orientation of the antenna.
The magnetic loop antenna wire

5 Nov 2013

GP antenna for four bands 28, 21, 14, 7 MHz

The figure shows the antenna GP for four bands : 28 MHz , 14 MHz , 21 MHz and 7 MHz . The main antenna - mast has a height of 9.95 meters, it is usual GP antenna for a range of 7 and 21 MHz for the other two antennas GP she is still supporting mast. This antenna - mast is earthed at the connection point and the ground is connected to the counterweight to the 10.5 m long ( 7MHz ) , 5.20 m ( 14MHz ) , 3.5 m ( 21mgts ) , 2.45 m ( 28 MHz ) . and inclined at an angle of 135 degrees, so it turns out that the input impedance of the three bands GP antenna is 50 ohm, allowing you to connect without any problems to connect the coaxial cable of the same resistance. This is most effectively four band antenna operates GP is in the range of 21 MHz , as in this range for the longest antenna - 3/4L mast contains a wavelength range of the counterweights to improve alignment with the cable. In the range of 7 MHz antenna GP consistent color across a transformer in the rest of the condensers . The disadvantage of this antenna GP - is that its base should be at a height of about 7 meters (to allow the angle of 135 degrees). Advantages that the antenna can be grounded.
antenna GP