Particular grovehorns are used as receiving components in radio telescopes. The horn mentioned above is the secondary focuses’ energizing antenna of the radio telescope of Effelsberg.
With a diameter of 100 meters this telescope is the largest totally adjustable antenna of the planet earth.
The radiations intercepted from space by the parabolic reflector is reflected at 23 GHz from a second, elliptic reflector (on of its combustion points coincides with the Parabols’s combustion point) to the second combustion point of the elliptic reflector. On the second point of combustion a hornantenna is installed to collect energy, which means that the horn is the actual antenna that leads the caught energy to the downstream delicate receiving system.
Those groovehorns are elaborate or even impossible to produce by cutting because of their geometry.
Galvano-forming offers a cost-efficient alternative for this process. A procedure was developed in colaboration with the MPI for radiostronomy in Bonn to fabricate complicated groovehorns with an extremely high relation of grooveheight to groovewidth of 6:1.
The horn is produced through a thick copper or nickel plating on meachanically easy to handle mainshape made of a AI-alloy (e.g AlMgSi0,5) on which the later crosspieces as grooves are lathed in.
A particular procedural step prevents pieces od electrolyte to stay in the grooves because this could lead to corrosions after a while.
Accoding to how big the horn is and which geometry it has the galvanic procedure is interrupted at a layerthickness of 2,5 mm to start treating the piece outside. Flanges or enhancements made of brass, bronze or other metals are applied it and – after another step – galvanised to the horn.
When the piece is done the aluminium mainshape is etched out again with a 15-20% sodium hydroxide solution at 60-95°C.