There are two common methods for matching antennas in a coaxial system: one uses a variable capacitor (like the one in your picture), and the other uses a more common 49:1 ferrite-core auto-transformer. The auto-transformer type uses a capacitor in series with the primary winding to compensate for losses at high frequencies, typically using a fixed 100pF value. Your example requires a variable capacitor to tune the LC circuit to resonate at the current operating frequency. While the variable capacitor approach is generally more efficient, it can be cumbersome to adjust each time you change frequencies. The 49:1 ferrite auto-transformer is much easier to use, so people don't worry too much about those losses.
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