Frequency tunable inverted-V HF dipole antenna using channel extension technique

The aim of this paper is to provide efficient technique for optimum performance of HF dipole antenna with minimum height variation. HF Frequencies are generally lower at the night and higher during the day due to ionospheric variations. Large range HF communication experiences limitation due to use of either multiple antennas or changing the antenna height at regular interval due to variation in HF frequencies. Various past research work w.r.t. HF frequency tuning focuses on either electrically small antennas or narrow band, dual band frequency tuning. However long range wide band HF antenna frequency tuning needed to be addressed. In present paper a channel length extension technique is used to vary the long range inverted V HF Dipole antenna resonance frequency while maintaining the actual Dipole length. With the employment of channel length extension technique most of day/night frequencies can be covered in a particular time slot resulting in very effective and accurate HF contact with least variation of antenna height. Resonance Frequency shifting (-3 M Hz) from 9.5 MHz to 6.5 MHz has been demonstrated by varying channel length for 10 M Hz inverted-'V' HF dipole antenna. Extensive trials were conducted to validate the performance results and same found as desired. The research work carried out in this paper will definitely enhance the efficiency of HF communication for various time slots and provide novel platform for optimum operational performance of HF antenna specially in the field of Defence and national security.