HF Helical Antennas: Theory and Practice

Measurement of the Input Impedance of Helical Antenna with an RF Bridge

Input impedance of the helical antenna was measured directly at antenna terminals. Figure 4 shows the method of measuring the impedance of a dipole helical antenna.

Figure 5 shows the method of measuring the impedance of a vertical helical antenna.

RF -bridge was connected to the antenna by short thick wires with length of not more than 10 centimeters.

RF generator was connected to the RF -bridge through a short length of a coaxial cable near 30 cm (1 foot) long. Several ferrite rings were installed on the both ends of the coaxial cable. RF generator was powered up by internal batteries. At the time I have not my lovely MFJ- 259. RF -bridge and RF generator were homemade ones. Reference 5 shows schematic of the RF -bridge. Reference 6 shows schematic of the RF generator.

Figure 4 Method of Measuring the Impedance of a Dipole Helical Antenna

Figure 5 Method of Measuring the Impedance of a Vertical Helical Antenna

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