Here are my understandings:
BALUN is a bi-directional balanced to unbalanced converter that can be used for non-balanced output of sound-boosting or semi-professional audio equipment, converted to professional and homogeneous input, and can be used in turn.
Balanced connector with XLRF-3 calorie head and connected XLRM-3 Canon head, can be used for balanced input and output, built-in first-class quality of the European plant audio transformer, the signal isolation to unbalanced lotus socket and connected Of the 6.3mm socket.
The unbalanced part is equipped with a ground connection switch to help solve the noise generated by the ground loop. When the switch is pushed to the left, the ground is set to a high impedance state: when the switch is pushed to the right, the ground is set to connect.
BALUN balanced to non-balanced converter, is the highest quality audio specifications to design, suitable for high quality requirements are used.
In addition, BALUN in the antenna design (such as dual dipole antenna) is responsible for the unbalanced transmission line into a balanced load! This makes the antenna pattern to achieve symmetry!
Balanced converters are devices that connect balanced transmission lines and unbalanced transmission lines. Balanced converter is a transformer: it can be unbalanced signal into a balanced signal, and vice versa. The balanced converter isolates the transmission line and provides a balanced output. A typical application of a balanced converter is the antenna of the television set. Its professional terms come from balance and non-equilibrium.
In the balance converter there is a pair of balanced terminal devices, the current is numerically equal, but the phase is reversed. There is also a pair of unbalanced terminal equipment, one end of the ground, the other end of the transmission signal. Balanced converters are widely used in wireless communications and cable communications.
The ways to make the balun come true:
Balun (Balun) is the English "balance - unbalanced converter" abbreviation transliteration. Its role in addition to the balance - unbalanced transformation, but also depending on the form of the balun, the structure can be carried out 1: 1,4: 1,6: 1,9: 1,25: 1 ratio of the impedance conversion. Principle is according to the antenna theory, the dipole antenna is a balanced antenna, and coaxial cable is an unbalanced transmission line, if the direct connection, the coaxial cable has a high-frequency current flow (according to coaxial cable transmission principle, High-frequency current should flow inside the cable, the skin is shield, there is no current), this way, it will affect the antenna radiation (you can imagine the cable shield is also involved in the radiation). Therefore, it is necessary to add a balanced balun between the antenna and the cable, the flow into the cable shield outside the current control out, that is, from the oscillator through the cable shield skin high-frequency current cut off. There are many ways to achieve this purpose:
One is the high-frequency open-circuit method, at the quarter of the cable shield edge of the wavelength of a quarter of the wavelength of the sleeve (equal to one quarter of the wavelength of the open line), because the quarter-wave open line The frequency as the open circuit, to cut off the role of high-frequency current, this approach, the work of narrow bandwidth, low frequency when the quarter-wave sleeve is very long, suitable for high-power high-frequency use.
The other is to offset the law, think of ways to make the flow of the same size in the opposite direction and cancel each other, the application of more magnetic ring three-wire balance between the balun is the case, this band is wide, Power is limited by magnetic saturation of the magnetic ring, suitable for low frequency low power use.
Another kind of transformer method, through the high-frequency transformer to achieve balanced unbalanced conversion, the principle is like a push-pull output transformer, the two-way balance current into a unidirectional unbalanced current. Transformers can be used around the core or hollow, suitable for high power use.
There is a way to suppress the law, the oscillator through a high-frequency choke connected to the cable shielding layer to prevent high-frequency current flow to the cable shield skin, this method is relatively simple, that is, about 10 turns around the magnetic ring Well, hollow also does not matter, generally low frequency around a few laps, the frequency of small round a few laps. But the suppression effect is not the above-mentioned several good, so the first few used for professional applications, this amateur application more.
Remember that we only cut off the high-frequency current of the shield's skin, not to cut off all the high-frequency current flowing to the shield (so that the oscillator and the cable will be broken), the high-frequency current is in the shield Inside the flow. The image can be a cable can be imagined as a water pipe, should be the water in the water in the stream, such as without barron, the water is not only in the water pipe flow, and some also flow to the tube of the skin. Barron's role is to prevent the run, run, drop, drain, forcing the water in the water pipe in the flow, unspeakable, one of the!
Common radio output is often unbalanced, common vertical antenna is also unbalanced, such as R7000 (vertical polarization of the dipole antenna is balanced input) generally do not have balun, impedance matching mainly through the matching circuit to adjust, And the angle of the antenna oscillator can also affect the input impedance. For the common inverted V antenna with the balun, it only plays the role of imbalance -> balance transformation, its impedance ratio is 1: 1. A certain height of the resonance at the target frequency of the inverted V antenna impedance adjustment, generally by changing the angle of the antenna to achieve. Eliminating the common inverted V antenna of the balun, directly on the antenna feed, although sometimes may not cause significant deterioration of the standing wave ratio, but the feeder outer cable will have the current, the feeder outer cable is also involved in radiation, forming a real Radiation of three radiators. This will cause the antenna radiation pattern to change, changing the length of the feeder will change the antenna standing wave ratio. As the presence of feeder radiation, close to the radio feeder TV, telephone, etc., often have TVI, TEL-I and other RFI.
Those are just my understandings. What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.
May someone would like to help ?
thanks in advance.