The D-layer only exists while the sun is shining on the atmosphere, and it eats low frequencies whole. At 3.5 MHz that absorption is total — in daylight, 80 meters goes nowhere.
WHY THE SUN IS UP, SO IT IS SHUT
The D-layer only exists while the sun is shining on the atmosphere, and it eats low frequencies whole. At 3.5 MHz that absorption is total — in daylight, 80 meters goes nowhere.
It dies within about an hour of sunset, and 80 comes alive fast. By full dark it will reach a thousand miles, and by midnight much further.
Winter is the season. Summer thunderstorms hundreds of miles away put a constant crackle on the band that can make it unusable on its own.
WHEN IT WORKS
BEST · Full dark, and best in winterWORST · Any daylightWATCH · Comes alive ~1 hr after sunset
WHO MAY TRANSMIT WHERE · 47 CFR §97.301
FREQUENCY (MHz)
MODE
LICENSE CLASS
3.500–3.525
CW
Extra
3.525–3.600
CW — Novice & Technician
Technician and above, General, Advanced, Extra
3.600–3.700
Voice
Extra
3.700–3.800
Voice
Advanced, Extra
3.800–4.000
Voice
General, Advanced, Extra
Is 80 meters open right now? The Ham Radio IQ app shows the MUF and LUF over your head this minute, whether this band is above or below them, and a map of real contacts being heard worldwide. See the board →