How can ignition noise in radio receivers be suppressed using ferrite beads?

Using ferrite beads to suppress ignition noise in radio receivers is most effectively done by installing them in the primary and secondary ignition leads. This technique works because ferrite beads are made of magnetic materials that suppress high-frequency noise by presenting a high impedance to those frequencies. When placed around the ignition leads, they can absorb and dissipate unwanted electromagnetic interference generated by the vehicle's ignition system, which can otherwise interfere with the radio signals.

The other options do not target the source of the noise as effectively. For instance, placing ferrite beads on the antenna may not be effective in suppressing noise originating from the ignition system, as the antenna is primarily responsible for receiving signals, not mitigating interference from other components. Similarly, using ferrite beads within the speaker wire or in the power lead could help with some noise issues but would not directly address the ignition noise generated externally. Therefore, the best approach is to focus on the ignition leads themselves, where the interference is directly produced.