The 5⁄8-wavelength antenna (Fig. 18-9) is popular on 2 m for mobile operation because it is easy to construct, and it provides a small amount of gain relative to a dipole. The radiator element is 5⁄8-wavelength, so its physical length is found from:
The 5⁄8-wavelength antenna is not a good match to any of the common forms of coaxial cables. Either a matching section of cable, or an inductor match, is normally used. In Fig. 18-9 an inductor match is used. The matching coil consists of 2 to 3 turns of no. 12 wire, wound over a 1⁄2-in OD form, 1⁄2-in long. The radiator element can be tubing, brazing rod, or a length of heavy “piano wire.” Alternatively, for low-power systems, it can be a telescoping antenna that is bought as a replacement for portable radios or televisions. These antennas have the advantage of being adjustable to resonance without the need for cutting.
(source : Practical Antenna Handbook by Joseph J. Carr)
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