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While the 20-meter band and higher frequencies are not significantly attenuated by D layer energy absorption due to their smaller wavelengths, absorption at lower frequencies is usually too severe for DX. While the 20-meter band and higher frequencies are not significantly attenuated by D layer energy absorption due to their smaller wavelengths, absorption at lower frequencies is usually too severe for DX. You can expect the 20-meter band to work to some extent both day and night. * Frequencies above 20-meter up to MUF propagate better at day.* Frequencies below 20-meter propagate better at night.