An article by two well-known radio amateurs, “Tuning Electrically Short Antennas for Field Operation,” appeared in Microwave Journal. Authored by QEX Editor Kai Siwiak, KE4PT, and award-winning researcher Ulrich Rohde, N1UL, the article points out that both Amateur Radio and military applications exist for 20-W battery-powered radios equipped with whip antennas. “In general, the whip antenna which makes the radio portable is not optimized for signal propagation: A whip antenna has no ground return or proper counterpoise,” the article notes. “While some users drag a wire of up to 8 meters behind, this is not an ideal solution.”
As the article explains, electrically short antennas — typically 0.1 λ or shorter — look like a capacitor, with a typical capacitance of 25 pF per meter of length. “At 2 MHz, where the wavelength is 150 meters, an inductor of 84 μH is required for resonance,” the article says. But just getting a good VSWR is not all there is to it.