Steep beam antenna
A high-beam antenna is a transmission antenna in the medium wave and short wave range, which mainly radiates vertically upwards.
The aim is to supply an area around the antenna with radio broadcasting without shrinking, by reflecting the emitted waves on the ionosphere. The reflection is angle-dependent and only works at characteristic, time-of-day and sun activity-dependent frequencies below a few megahertz. Therefore, such antennas are also used to study the ionosphere.
construction
A steep beam antenna consists of a dipole antenna stretched between two towers or masts . Cross dipoles are also occasionally used. These are usually fed with a phase shift of 90 degrees ( circular polarization ).
Examples
A steep-beam antenna for studying the ionosphere is located in Juliusruh on the island of Rügen . The antenna sends frequencies between 1 and 30 MHz to the ionosphere and evaluates the reflected signals. This ion probe monitors the ionosphere as part of a worldwide network of such probes.
For radio coverage, the RIAS (later Deutschlandradio ) broadcast between 1978 and 1995 with a steeply radiating crossed dipole antenna on the frequency 990 kHz from the Berlin-Britz transmitter at night with circular polarization and a transmission power of 300 kW. This antenna enabled better coverage of the GDR area . Broadcasting ceased in 1995 due to lack of electromagnetic environmental compatibility .
In the GDR, for its part, the program Radio DDR I was broadcast with a steep-beam antenna from the Burg transmitter on the frequency 1575 kHz. Megaradio also used this antenna between 2002 and 2003 to broadcast its program on this frequency.
Another steep beam antenna was located at the transmitter in Mainflingen until the mid-1980s .
The Swiss radio operated a steep beam antenna for the frequency of 1566 kHz near the Sarnen national broadcaster, which has since been decommissioned.
See also
- Shrinkage-reducing antenna (flat distribution)