Frequency in MHz Wavelength in meters: a.m. broadcast 1.8 3.5 7.0 14.0 21 28 50 . . . 600-200 160 80 40 20 15 10 6 . . . ---------------------------------------------------------------------- | . | . | . . . very heavily attenuated | . | . | . . . | less | . | . . . attenuated . | . . . | . | low | . . . | . attenuation . . . | . | . | little to no | . | . | . attenuation . . . | | . | . . . ------------------------------+-------+-------+----------------------- | . | . . . | . | . . . heavily propagated . . . | . | . rapidly (ground wave) (skip) | . | . decreasing . . . | . | . . . ------------------------------+-------+-------+----------------------- | . | . . . these frequencies this one . . . work mostly in the will go . . . evenings . . . . . . . . . . . . during . these may . . . the day . . . | . | . . . ------------------------------+-------+-------+-----------------------
ASCII Description: The above table is in ASCII art — just happened to be lying around like that for about 16 years now (did it in Wordstar!). It is a tabular depiction of the relationship among frequency (wavelength), attenuation, and propagation: lower frequencies propagate (ground wave or skip) but are attenuated; higher frequencies are not attenuated but do not propagate, either; best choices are in the middle range of about 20 meters. [return to reference]