Indigenous development of a RFI shielded cabinet for electronic assemblies

Summary form only given. A low-cost RFI-shielded all-aluminium cabinet has been indigenously designed and developed to house the electronic sub-assemblies of the Giant Metrewave length Radio Telescope (GMRT) receiver. The cabinet is about 600 mm wide, 750 mm deep and 2100 mm high. The frame uses specially developed extrusions and incorporates the facility to plug in and mount standard 482.6 mm (19") wide sub-racks with a total height of 42U (1866.9 mm) from both the front and rear. The side walls of the cabinet use full size aluminium sheets which are inserted into grooves provided in the frame. To improve the shielding effectiveness, additional L-members are rivetted to the side wall with a pitch of 50 mm around the periphery. The L-members are then screwed to inserts provided in the frame with a pitch of 50 mm. The top and bottom walls of the cabinet have a double-layer honeycomb mesh to ensure ventilation without sacrificing the shielding effectiveness. The front and rear doors incorporate full height hinges along one of the heights, screwed to inserts provided in the frame, with a pitch of 50 mm and provide an opening angle of around 130 degrees. Knitted wire mesh gaskets around compressible neoprene former are fixed to a flat face provided in the other three sides of the frame. The extrusion has necessary stops to avoid over-compression of the gasket. The door has a simple three-point locking system. Preliminary testing of the cabinet indicates a shielding effectiveness of around 60 dB at 300 MHz, dropping down to around 45 dB at 1000 MHz. Detailed testing is planned in the near future