送信者: Junichi Nakajima 宛先: ; 件名 : VSI-H questionnaire (MDR connector) 日時 : 2001年3月1日 0:43 Dear Whitney-san, TDC coordinator, Thank you about VSI-S and I think you are busy with them but now I have to tell you a problem arised with VSI-H. We have found several difficulties under implementation of VSI-H to the real existing hardwares. 1. MDR connectors 1-a: The VSI-H direct MDR-80 with 4-40 jackscrews. The 4-40jackscrew is not metric and they are impossible to find here. Only the 3M in U.S. supplying the connector mating inch screw. In addition, even they are in metric, the MDR shell with metric jackscrew is not popular at all. I remember that I stressed jackscrews lock for the DAS and DIM which mounted in tilting telescopes. Now I firmly believe the jack screw should be optional for these special situation. Latch lock is normal usage for the MDR users. Otherwise many VSI-H engineers will troubled with the inch/metric, connector and cable configuration as I had been confused recently. Fortunately, the VSI-H refer 3-M receptacle N102XX series has studs for latch. We will use similar one with metric screw hole in Japan and we will use the latch to lock a connector. The jackscrew shell will be used in special case. I propose you to change the VSI-H to exclude the word 'jack screw' or change them to 'optional: jack screw lock'. Please understand that, provisionally Japanese group will use latch lock receptacle and connectors. We have no other choice. (BTW, The 3M changed their Web and VSI-H refer URL does not work.) 1-b. The VSI-H direct a 3M foil pleated MDR cable assembly as an example. Although they expecting 100 ohm impedance, it seems the specified differential pinout will not locate neighboring location in the flat cable. Our local cable vendor does not used pleated foil type. Cables which bring into IVS-TOW by Koyama-san will be a round shielded cable. Best Regards Junichi Nakajima　nakaji@crl.go.jp CRL,KSRC, Radio Astronomy Applications 34m Radio Telescope VLBI Group　 +81-299-84-7145　+81-299-84-7159