Saturday, August 17, 2013

aperiodic ferrite baluns for harmonization antennas

For balancing and harmonizing Ham antennas can be used aperiodic ferrite baluns. These devices can operate in the Amateur Radio HF and VHF bands. These aperiodic balun on their wires occur with the same high-frequency currents in the opposite direction, resulting in a ferrite core simmeriruyuschego devices resulting magnetic field is zero. If the load (antenna) that there is an asymmetry in the ferrite appears not compensated magnetic flux. Depending on the size of the ferrite core and the wire cross-section aperiodic balun can be used on the transmitter power is a few milliwatts to several kilowatts. To match the antenna can be used by various schemes aperiodic ferrite baluns. The following figures show these schemes.
This figure shows a diagram of a balun with crown windings, it does not produce the transformation of input and output impedance. One of the windings is needed to improve the characteristics of the ferrite balun in the range of 28 MHz amateur radio. The two windings are wound bifilar and one separately.

For balancing and alignment of antennas with a high input impedance can be used a second-figure, in this scheme, the transformation of the input and output resistance by a factor of 1:4. In order to be symmetry was in all the bands to perform the winding so that would be between the wires was a small and constant distance along the winding. This scheme provides a good agreement with a coaxial cable with an impedance of 50 ohms ... 75.

For balancing and alignment of antennas with low resistance can apply an apparatus as shown in the figure. The input impedance of the antenna may be approximately 20 ohms. The transformation ratio 4:1 zeal.

To change the transformation ratio of the ferrite aperiodic balun can apply this scheme. The transformation ratio can be varied from 1:4 to 1:10

If you need to agree on an asymmetrical antenna and asymmetric power line that is now such a scheme, with a ratio of 4:1.

This scheme is applied on a ferrite ring if necessary to carry out a phase shift of 180 degrees in an unbalanced line.

Ferrite matching devices do not make a large attenuation in the antenna gain and is resistant to momentary overloads.