Each transmitter should have which three protections?

• A. Isolator, Low Pass Filter, Band Pass Cavity
• B. Isolator, High Pass Filter, Band Pass Cavity
• C. Isolator, Low Pass Filter, Notch Filter
• D. Isolator, Low Pass Filter, Band Pass Filter

Answer: (A)

Protecting a transmitter involves keeping reflected power from reaching the transmitter, and shaping the output spectrum to stay within the licensed band. An isolator is used to block and absorb any reverse power from the antenna, shielding the transmitter from damage due to VSWR. A low‑pass filter then attenuates harmonics and other out‑of‑band energy before it can be radiated. The band‑pass cavity provides sharp, high‑power filtering around the desired band, ensuring the transmitted signal stays within its allocated spectrum and minimizes spurious emissions. Cavities are particularly robust for high‑power applications and offer strong out‑of‑band rejection, which is why they’re chosen over a simple band‑pass filter in this protection trio. High‑pass filters would not adequately suppress low‑frequency or wide‑band harmonics, and a notch filter only removes a single frequency, leaving other out‑of‑band energy unchecked.