Question 22B3

Adding a series capacitance to an antenna electrically shortens it. Here's why: 1. **Resonant Frequency and Electrical Length:** An antenna's resonant frequency is inversely proportional to its electrical length. A shorter electrical length corresponds to a higher resonant frequency, and vice-versa. 2. **Effect of Series Components:** * Adding a series *inductor* (loading coil) makes an antenna resonate at a *lower* frequency, effectively *electrically lengthening* it. * Adding a series *capacitor* makes an antenna resonate at a *higher* frequency, effectively *electrically shortening* it. 3. **Explanation for Capacitance:** By introducing series capacitive reactance, you shift the antenna's natural resonant frequency upwards. This upward shift in resonant frequency means that, for any given operating frequency, the antenna now behaves as if it's *electrically shorter* than it was before the capacitor was added. Therefore, option B is correct because series capacitance raises the resonant frequency, which is equivalent to electrically shortening the antenna. * **A) It electrically lengthens a physically fixed length antenna.** This is incorrect; series *inductance* lengthens an antenna. * **C) It lowers the resonant frequency of a physically fixed length antenna.** This is incorrect; electrically shortening an antenna *raises* its resonant frequency. * **D) It increases the bandwidth of a physically fixed length antenna.** This is incorrect; adding reactive loading (either inductive or capacitive) generally *reduces* the bandwidth of an antenna compared to a full-size resonant antenna.