Friday, November 15, 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

Monday, November 4, 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