Baron: The Structure Of The Antenna.

Balun is balun, English, principle is according to the antenna theory, dipole antenna is balance type antenna, and the coaxial cable is not balanced transmission now, if it is directly connected to the casing of the coaxial cable with high frequency (according to the current flowing through the coaxial cable transmission principle, high frequency current should flow in internal cables skin is a shield, there is no current), as a result, it will affect the antenna (radiation shielding layer can be imagined as the cable is also involved in the wave radiation). KS|

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Therefore, we should join the balun between the antenna and cable, the cable shielding layer into the current external control off, that is from the oscillator through the cable shielding sheath high-frequency current interruption. There are many ways to achieve this purpose, one is the high frequency open circuit method, in the cable shielding layer of the outer layer of the four points of a wave of strengths to connect a 1/4 wavelength sleeve GH

(equal to the effect of 1/4 wavelength, wavelength 1/4 open line) for open line on the frequency as open, reached the truncation of high frequency current, this way, bandwidth, low frequency when the 1/4 wavelength sleeve becomes very long, suitable for high power and high frequency to use. The other is the offset method, which can be used to offset the current magnitude of the current flowing in the same direction, using HeF5>mn!

More with three magnetic rings winding balun is this, the frequency band is wide, but the use of high power by magnetic saturation limit, suitable for low frequency low power use. A transformer balun realization method, through the high frequency transformer, a push-pull output transformer as principle, the bidirectional balance current is converted to current but to balance. Transformer can be xc`

The core or wound into a hollow, suitable for large power use. There is a suppression method, a high frequency oscillator through the choke cable shielding layer of skin, prevent high frequency current flow to the outer layer shielded cable, this method is relatively simple, is to put the cable around the ten laps around the wound on the magnetic ring hollow better, also never mind, is generally low frequency around a few laps, high frequency around a few times. But the inhibitory effect is not slqd*jQc/A

There are several good, so in front of a few more for professional applications, this amateur applications more.