送信者: Alan R. Whitney 宛先: Wayne Cannon ; Brent Carlson ; Dick Ferris ; Dave Graham ; Nori Kawaguchi ; Tetsuro Kondo ; Sergei Pogrebenko ; Misha Popov ; Jon Romney ; Ralph Spencer ; Alan Whitney 件名 : Fwd: Re: VSI-H questionnaire (MDR connector) 日時 : 2001年3月10日 7:34 Gentlemen, I apologize for being a little slow to forward to you this note from Nakajima-san regarding the lack of a frame ground in the VSI-H specification and difficulties with MDR-80 jackscrews. Comments and suggestions are welcome. A timely response would be appreciated. Regards, Alan >To: nakaji@crl.go.jp, awhitney@haystack.mit.edu, kondo@crl.go.jp >Subject: Re: VSI-H questionnaire (MDR connector) >From: Junichi Nakajima >X-Mailer: Winbiff [Version 2.11 PL1] >Date: Mon, 5 Mar 2001 22:49:53 +0900 > > >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$B!!(Bnakaji@crl.go.jp >CRL,KSRC, Radio Astronomy Applications >34m Radio Telescope VLBI Group$B!!(B >+81-299-84-7145$B!!(B+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$B!!(Bnakaji@crl.go.jp > > CRL,KSRC, Radio Astronomy Applications > > 34m Radio Telescope VLBI Group$B!!(B > > +81-299-84-7145$B!!(B+81-299-84-7159 > >