Antennas An alternative mode in HF mobile antennas

摘要

SIMPLE MOBILE. The vertical whip antenna is the most popular antenna for mobile use. The easiest way to feed such an antenna is to make it a quarter wavelength long at the frequency in use, which allows it to be fed directly with 50Q coax at the low impedance base. The resonant quarter wavelength is a function of frequency and is 1.48m (58.5in) on 50MHz, 2.5m (8ft 2in) on 28.4MHz and progressively shorter on the higher VHF bands. Quarter wave antennas on the 28MHz bands and higher are quite practical, but on the lower HF bands it is a different matter. Even on 21MHz, a quarter wavelength is 3.45m (1 lft 2in) and on 14MHz is4.99m (16ft 4in). It follows that a practical mobile antenna for the HF bands must be shorter than a quarter wave.