From 30 meter down in frequency are the nighttime bands of 30, 40, 60, 80, and 160 meters, known as the Low Bands. These bands are throttled during the daytime hours by absorption in the lower layers of the ionosphere. After the sun begins to set, these bands start to come alive. First, 30, 40, and 60 meters may open in late afternoon and stay open somewhat after sunrise. 80 and 160 meters, however, make fairly rapid transitions around dawn and dusk. Signals between stations operating on 80 and 160 meters often exhibit a short ( 15 to 30 minute ) peak signal strength when the easternmost stations are close to sunrise. This is known as the dawn enhancement. This time is good for stations with modest equipment to be on the air and take advantage of the stronger signals on these more difficult DX bands.
160 meters is known as Top Band because it has the longest wavelength of any current amateur band. This long wavelength requires larger antennas. Add in more atmosphere noise than at higher frequencies and you have a challenging situation. That is why some of the most experienced Dxers love Top Band Dxing. Imagine trying to receive a 1 kilowatt broadcast station halfway around the world. That is what the Top Band Dxer is after! As difficult as this task sounds, many of the top Dxers have managed it.
by Ward Silver, N0AX
Good Luck For Your Dxing!!!