If you are going to describe propagation for SBE certification questions (RWEE, April 15), at least do it correctly. Your description on page 6 for the power question states: “During the daylight hours the ionosphere layer of the earth’s atmosphere is ionized by the sun and medium-wave signals pass through into outer space. At night, without solar heating, the atmosphere ‘hardens up’…”
Quite the opposite occurs: During the daytime the D layer thickens and absorbs LF radio waves so they can’t reach the E and F layers to be reflected. At night without the presence of as many solar particles (not so much heat), the D layer thins or goes away altogether to allow the low-frequency waves to reach the E and F layers to be reflected.
I realize the question was about FCC rules, but nonetheless, if we are helping future CEs learn, let’s not feed them misinformation.
Paul A. Litwinovich
Director of Engineering
Technical Editor Michael LeClair replies: Your description of ionospheric reflection is much better than ours so we are reprinting it in full.