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.

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.

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.

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.

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.