Skew is a term used in
antenna engineering. It is a technique to improve the horizontal
radiation pattern
In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: “A ...
of a high power
transmitter station
A transmitter station or transmission facility is an installation used for transmitting radio frequency signals for wireless communication, broadcasting, microwave link, mobile telephone or other purposes.
Choice of location
The location may b ...
.
In a high power
VHF
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter.
Frequencies immediately below VHF ...
or
UHF
Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
station, usually the antenna system is constructed to broadcast to four directions each separated 90° from each other. So the directivity of the antenna system resembles a
four leaf clover
The four-leaf clover is a rare variation of the common three-leaf clover. According to traditional sayings, such clovers bring good luck, though it is not clear when or how this idea began. One early mention of "Fower-leafed or purple grasse" i ...
. While settlements within the
main lobe receive enough energy, the energy received by the settlements between the main lobes may be 6 dB less.
One popular method to solve the problem is to skew the antenna panels symmetrically around the central axis of the mast.
[R.Busi: ''High altitude VHF and UHF Broadcasting stations'', EBU technical center, Brussels, 1967 p 25] Usually a skew of λ/4 gives the desired almost-uniform horizontal radiation pattern. But in cases where more than one
RF signal is applied to antenna system (via
combiner
Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmiss ...
), the improvement in the horizontal radiation pattern may be inadequate for some signals.
References
{{Analogue TV transmitter topics
Antennas (radio)
Broadcast engineering