I've been studying the U.S. license examination question pools. For the most part, it is reasonably obvious what the questions and answers mean even when I am not yet able to come up with the answers on my own. However, the correct answer to this question in the Extra class pool is confusing me:
How can conducted and radiated noise caused by an automobile alternator be suppressed?
A. By installing filter capacitors in series with the DC power lead and by installing a blocking capacitor in the field lead
B. By installing a noise suppression resistor and a blocking capacitor in both leads
C. By installing a high-pass filter in series with the radio's power lead and a low-pass filter in parallel with the field lead
D. By connecting the radio's power leads directly to the battery and by installing coaxial capacitors in line with the alternator leads
What is the purpose of specifying “coaxial” capacitors? Why does it say “in line”, which in the absence of further information I would interpret as “in series”? I would think that low-pass rather than high-pass filtering would be desirable.
Is this just a sloppily phrased answer, or is there something subtle here?