送信者: Junichi Nakajima 宛先: ; ; 件名 : Re: VSI-H questionnaire (MDR connector) 日時 : 2001年3月5日 22:46 Dear Whitney-san, TDC coordinator, Hi,again. Another VSI-H unsatisfactory issue turned up. 1-c: Frame Ground missing. In the VSI-H pin out there is no Flame Ground (FG) description. This is faulty situation as an electric interface specification. A manufacture engineer claimed us to write. Without the FG, floating voltage between the units will damage LVDS devices when they are connected in worst case. I remember we discussed the issue in early stage and we agreed to allocate the FG to cable connector chassis/shell. the chassis are connected shielded wire each end. Since most of the pin are already occupied by optional purpose this is the favorite way to do. These kind of technical issues will appear continuously. I do not want to bother you each time by these case to promote next VSI-S. Any VSI-H self consultation process are welcome. 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 > 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 >