The Mountain Trail
HF signals reach long distances by bouncing off the , layers of charged gas 50-400 km up. The absorbs lower HF signals during the day and fades at night, which is why 40 and 80 meters open up after dark. The does most long-distance reflection. The maximum usable frequency () is the highest frequency that will bounce between two points. Sunspots charge the ionosphere and follow a cycle of about 11 years, so the high bands are best near solar maximum.
Level 3 · Lesson 3.1
Propagation: how signals travel far
“Some nights 40 meters opens up and you are talking to Ireland from a cabin in Pocahontas County. That is the sky doing you a favor.”
You'll be able to
explain ground wave, sky wave, and the ionosphere, and predict band conditions by time of day.
Tap an underlined word for its meaning.