POLARIZATION OF ELECTROMAGNETIC WAVES
Electromagnetic waves travel away from the wire in horizontal, vertical, slanted, or circular waves.
If the antenna wire runs horizontal or parallel to the earth, the radiation will be horizontally polarized.
A wire or conductor that runs at right angles to the earth produces vertical radiation.
A slanted wire has components of both horizontal and vertical radiation.
Crossed wires connected by proper phasing lines that shift the phase from one wire to the other wire by 90 degrees will produce circular polarization.
Amateurs working orbiting satellites at VHF, UHF, and microwave frequencies use circular polarization.
When your high frequency signals are reflecting off the ionosphere, it isnt important if the other stations antenna has the opposite polarization from yours (the polarization does matter for line of sight communication).
The reflected polarized waves passing through the ionosphere are slowly rotated causing fading signals (QSB).
The reason the polarization of antennas is most important is that it determines the angle of radiation.
Horizontally polarized antennas at ordinary heights used by hams produce mostly high angle radiation and weaker low angle radiation, but this doesn’t mean there is no
low angle radiation. It is there but is weaker than high angle radiation.
However, you must put a horizontally polarized antenna up more than one-wavelength high to get a strong low angle radiation.
One wavelength is 280 feet on 80 meters, 140 feet on 40 meters, and 70 feet on 20 meters.
High angle radiation works nearby stations best and low angle radiation works distant stations (DX) best.
A vertically polarized antenna produces mostly low angle radiation, with its high angle radiation being weak.
For this reason, vertical antennas do not work as well as horizontal antennas do at ordinary heights for working stations less than about 500 miles away.