antenna impedance การใช้

• The antenna coupling transformer also functioned as an impedance matching transformer, that allowed a better match of the antenna impedance to the rest of the circuit.
• Unbalanced currents that may otherwise flow on the cable will make the measured antenna impedance sensitive to the configuration of the feed cable, and the radiation pattern of small antennas may be distorted by radiation from the cable.
• Therefore, in improved receiver circuits, in order to match the antenna impedance to the receiver's impedance, the antenna was connected across only a portion of the tuning coil's turns . adjustment of both the resonant frequency and the turns ratio.
• In one simple example, " Balanis " performs this computation to find the antenna impedance with different " N " using Pocklington's method and finds that with " N " > 60 solutions have approached their limiting values to within a few percent.
• Instead of altering thickness or spacing, one can add a third parallel wire to increase the antenna impedance 9 times over a single-wire dipole, raising the impedance to 450 Ohms, making a good match for window line feed cable, and further broadening the resonant frequency band of the antenna.
• :: : You can " approximately " convert electric field strength ( volts / meter ) to radiant intensity ( watts per square meter ) by squaring and dividing by the antenna impedance; in practice, you need to account for the antenna matching properties, impedance of free air, antenna directivity, and so on.
• Also, in the part of the near field closest to the antenna ( called the " reactive near field ", see below ), absorption of electromagnetic power in the region by a second device has effects that feed back to the transmitter, increasing the load on the transmitter that feeds the antenna by decreasing the antenna impedance that the transmitter " sees ".
• Along with transceivers and separates, the 4-Line included a set of matching accessories including the L-4 linear amplifier, C-4 control console, W-4 and WV-4 power meters, transmit and receive converters for the 50 MHz ( 6 meter ) and 144 MHz ( 2 meter ) bands, and antenna impedance matching networks ( tuners ), the MN-4 and MN-2000.