NATONAL RADO ASTRONOMY OBSERVATORY Charlottesvlle, Vrgna January 2 2, 986 To: VLBA Electroncs Group Proms Dck Thompson Subject: Rack and Module Plan for VLBA Electroncs The VLBA electroncs subsystems that are beng constructed at NRAO wll occupy three racks, two n the Antenna Vertex Room and one n the Equpment Room of the staton buldng. Ths memorandum outlnes the plan for the arrangement of equpment n these racks. The nomenclature and numberng system for racks and modules wll use the same system as the VLA f whch s descrbed n VLBA Techncal Report No. 31, but extended as necessary to ncorporate the new equpment. Type numbers for modules wll consst of a letter desgnatng the subsystem (see p. 9-3 of VLA T. R. No. 31) and a number whch wll start at 101. Ths number wll dstngush the VLBA modules from VLA modules, for whch type numbers start at 1. The two racks n the vertex room wll be attached to the room at celng level, and wll be of the same specal desgn as the VLA B rack. The rack n the Equpment Room wll be a commercal type wth sheldng to prevent radaton of nterference. Rack A, Front-End Control Rack Rack A s the Front-End Control Rack and wll contan FrontEnd control modules (F101) and power supples. t s located n the Vertex Room. The bn and module locaton s shown n Fg. 1. The Front End control modules are of sngle-slot wdth, and two bns wll provde locatons for up to 12 modules wth alternate slots empty for ar flow. The number to be used wll depend upon the number of front ends eventually nstalled. For the purpose of ths plan we assume that the number wll be about ten, and that one module desgn can be used for all front ends. There wll be two bns of power supples whch wll contan at least one each of power supply modules P101, P102, P103, and P1Q4: see Table 1 for a l s t n g of the modules. Power supples n Rack A wll provde the DC power for all of the electroncs n the Vertex Room,. e. for the front ends and the electroncs n both racks (A and B ). Note that the poston of the bns n Fg. 1 have been chosen for convenence on the assumpton that the floor to celng dstance n the vertex room s approxmately 95 nches. These postons should be consdered to be tentatve at ths tme. 1 No.Sl
Rack B r F/LO Rack Rack B wll contan the converter modules, local oscllator modules, and the swtchng to select the requred F and LO sgnals. Snce the phase stablty of the equpment s crtcal, no power supples wll be mounted n ths rack. A schematc dagram showng the nterconnecton of the 15 modules ncluded s shown n Fg. 2. These modules wll occupy four bns, whch wll be at the top of rack B to mnmze the lengths of the cables to the front ends. The postons of the swtches and modules are shown n Fg. 3. The swtches are mounted on back panels of the bns n a manner desgned for easy replacement of swtches n case of falure. The bn slots n front of the swtch panels wll be left empty. Rack C f Master L O Rack Rack C s located n the Equpment Room of the staton buldng. t contans the modules that transmt the reference sgnals derved from the maser to the Vertex Room and measure the round-trp phase (L102 and L103), and the montor and control nterface module for the hydrogen maser L101. t also contans power supples for these modules. Two bns wll be requred, wth the power supples n the upper one. t s proposed that Rack C be procured as one of a par of shelded racks that are bolted together as a sngle unt. The other one would be the F Dstrbutor Rack (Rack D ), the contents of whch are beng fabrcated by Alan Rogers' group at Haystack. t s possble that the modules n racks C and D could use some common power supples. Please gve me any comments on the above plan. We can dscuss t n more detal at the next electroncs meetng (Feb. 6 ). 2
T?ble. Prelmnary Lst of VLB A Module Types Module Name Type Number Wdth n Bn-Slot Unts Desgners Front End Control F101 1 E. Schlecht/W. Wreman Maser nterface L101 1 E. Schlecht/W. Wreman LO Transmtter L102 2? R. Bradley Round-Trp Montor L103 2? R. Bradley 2-16 GHz Synthesser L104 3 R. Mauzy/L. Beale LO Recever L105 3? R. Bradley 9.4 GHz Oscllator L106 2? R. Mauzy/L. Beale Swtch Drver L 07 1? E. Schlecht/W. Wreman 15VrlOA Power Supply P101 4 A. R. Thompson/W. wreman 15V,5A Power Supply P102 3 A. R. Thompson/W. Wreman 5V Power Supply P103 3 A. R. Thompson/W. Wreman 28V Power Supply P104 3 A. R. Thompson/W. Wreman 330 MHz Converter T101 2 E. Schlecht 610 MHz Flter T102 2 E. Schlecht 1.5 GHz Converter T103 2 E. Schlecht 2.3 GHz Converter T104 2 E. Schlecht 4.8 GHz Converter T105 2 E. Schlecht 8.4 GHz Converter T106 2 E. Schlecht 10.7 GHz Converter T107 2 E. Schlecht 15 GHz Converter T108 2 E. Schlecht 22 GHz Converter T109 2 E. Schlecht 3
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