Comparison of mechanical and electrical downtilt
Engineering is often about balance and that includes weighing whether to use mechanical or electrical downtilt in an antenna.
“There are advantages on both sides,” notes ATDI managing director Peter Paul. “One particularly practical consideration is that electrical downtilt has to be built-in by the manufacturer whereas mechanical downtilt can be adjusted by the installer which gives the end user a lot more scope to create the antenna that best suits their needs.”
Some engineers consider electrical downtilt better for use on omnidirectional antennae as it reduces interference in 360 degrees. “You can point the main gain of the antenna below the horizon and limit interference all round,” Peter comments. “In other circumstances, you can use mechanical downtilt so that the antenna’s back lobe is pointing in the air and reduce the potential for interference that way.
“But this is an area where end users get choices so it’s always wise to look at the advantages of each option in any given situation.”
● The downtilt angle varies over the horizontal beam width. Patterns
measured ±90° from the centre of the beam have decreasing
tilt angle until there is no tilt 90° from the main beam
● The horizontal half-power beam width increases with greater
● The resulting gain reduction depends on azimuth direction.
● There’s a uniform downtilt over the whole azimuth range
● The horizontal half-power beam width is independent of the
● There is an identical gain reduction in all azimuth directions.