Design and analysis of Slimjim dual band VHF and UHF antenna with crossarm variation

摘要

Most wireless communications need more than one band frequency to operate due to many reasons. Amateur radio, military operators and commercial mostly use either multiple antennas for different bands, that operates on any number of frequency bands. This situation also occurs in very high- frequency (VHF) and ultra high-frequency (UHF) bands. In this research, Slimjim antenna has been implemented on the VHF and UHF bands. Slimjim antenna was designed to work at 146 MHz for VHF band and at 443 MHz for UHF band, by adding a crossarm compensating element. This element was made by aluminum with 5 mm diameter. The antenna was measured in order to obtain some parameters such as resonant frequency, S11, bandwith, gain and radiation pattern. The measured results show that Slimjim-cross antenna resonates at frequency 154 MHz with S11 -32.65 on the VHF band, and at the frequency 457 MHz with S11 -36.82 on the UHF band. The qualitative test by implementing Slimjim-cross antenna with handy-transceiver radio shows that Slimjim-cross antennas can be used for communication as far as 390 meters on VHF band and 1100 meters on UHF band. By comparison, the original Slimjim antenna has 350 meters range for communication and -11.74 for S11 on the VHF band.