CESTRON HR

GENERAL DESCRIPTION

DIRECTIONAL CURTAIN ANTENNAS ARRAYS

When sectional coverage is desired, directional antennas are the proper choice. Curtain antennas provide not only high antenna efficiency, but also highest tolerances when faced with unfavourable environmental conditions. As per ITU publication from May 11th 2001 «Transmitting Antennas for HF Broadcasting» a special code is used to describe curtain antenna arrays with a periodic screen reflector. In its general form, the antenna is designated by AHRS m/n/h, whereby:

A Aperiodic
H Horizontal polarisation of the antenna
R Existence of a reflector screen
S The possibility of beam slewing
m Number of half-wave elements in each horizontal row [typical ranges are 2 or 4]
n Number of rows spaced half a wavelength above each other [typical ranges are 2,4 or 6]
h Height above the ground [bottom dipole row in wave lengths; typical range is 0.25 - 1.0]

State of the art design allows curtains to be operated over the frequency range of one octave, covering up to six adjacent frequency bands out of the shortwave broadcasting spectrum as defined by WARC.


CLASSICAL DESIGNED CURTAIN ANTENNAS ARRAYS

Fixed curtains consist of half-wave folded or full-wave open and multiple wire cage dipoles. The dipole feeding system is based on broadband design, which means dipoles are switched in parallel to subgroups. These subgroups are switched in parallel to subsystems, until the common feed point is reached.

Dipoles and their feeding system as well as the reflector screen are suspended to towers or masts in a way that they can be lowered separately for maintenance. A counterweight system is fixed directly to ground at one end, and at the other end, fixed to ground by a follow up mechanism. This counter-weight system makes sure that strong winds cannot damage the dipoles, the feeding system or the reflector screen. Curtains may be arranged back-to-back or side-by-side and may be suspended individually or collectively between suitably dimensioned guyed or self-supported towers. Slewing of the main beam direction can be realized by switching delay lines in and out. If a large number of different azimuth angles needs to be covered with radio signals, the antenna arrays may be installed in either a star or a polygon shape layout.

Technical Highlights: RIGID CURTAIN ANTENNAS ARRAYS

The rigid dipole technology combines the advantages of curtain antennas with the design principles as implemented in rotatable shortwave antennas. The resulting integrated system consists of rigid dipoles and a self-supporting structure with a central shaft. The components of the rigid dipole antenna are easily accessible. The system maintainability is greatly simplified due to the fact that there are no moving parts like halyards, steel ropes, counterweights etc.

Technical Highlights:
KEY FEATURES
  • Optimized gain in accordance with specific broadcaster needs
  • Highest radiated energy to target area for best antenna efficiency
  • Maximum performance
  • Highest Efficiency
  • DRM capability (full frequency range)
  • Fast installation, best reliability and maintainability
  • Low cost of ownership (entire life cycle)
  • Robust and rugged design suitable for extreme environmental conditions
  • Rigid antennas: dipoles for increased mechanical stability
  • Rotatable curtain antennas: highest flexibility to cover the whole short wave range. Adaptation of transmission parameters by remote control