Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!umich!umeecs!msi.umn.edu!cs.umn.edu!dmshq!com50!kksys!jhereg!imp From: imp@jhereg.osa.com (Charles T. Lukaszewski) Newsgroups: comp.dcom.lans Subject: Re: Thin Ethernet signal loss @ connectors Keywords: Data leaking out all over the place Message-ID: <1990Oct25.010241.7741@jhereg.osa.com> Date: 25 Oct 90 01:02:41 GMT References: <6464@bgsuvax.UUCP> Sender: Chuck Lukaszewski Followup-To: imp@osa.com Organization: Open Systems Architects, Inc. Lines: 49 In article <6464@bgsuvax.UUCP> jyoull@bgsuvax.UUCP (Jim Youll) writes: >I hope this doesn't sound too dumb, but here goes... >On a Thin Ethernet segment, is there significant signal loss at >each "T" connector? There is loss and attenuation, which is why the 10-Base2 specification limits thin ethernet segments to 30 "breaks" which include either barrel connectors or T connectors. However, it makes no difference whether the T is connected or not. You should give careful thought to how you plan to run your thinnet if it is to move between rooms. One implementation we frequently find at client sites is the use of a double-bulkhead on the wall, with one connector being used for 'in' and one used for 'out'. Remember, each barrel counts as a cable break, so a room with such a contraption and one station would have used 1/10 of your available breaks. >We are looking at options for prewiring a building. 10base-T is >preferred, but cost is a big problem and Thinnet is fast and cheap. >I've been asked to find out about leaving ready-to-go connections in the >walls with barrel connectors or T-connectors at each workstation, I urge you to really work out the costs of twisted pair versus thinnet. On every building-size install we have done, the costs ended up being comparable at worst, and twisted-pair far cheaper at best. As Kent Englund and others have pointed out here, there are a lot of hidden costs with thin net, and even if the up-front cost is somewhat less, I guarantee you that the medium and long-term investment in new cable, new connectors, move/add/change management and aspirin will be *substantially* more. You may want to seek out a qualified LAN consultant in your area that understands the types of systems you want to connect that can lay out the issues and costs more clearly for you. One final thought - be *extremely* careful about what kind of cable you install and make certain that the craftsmanship of the installation team is excellent. Virtually every thinnet system we've troubleshooted has had at the root of its problems poorly-installed, damaged or wrong cabling. Make sure you are using 50-ohm RG58/U, rather than 53-ohm RG58. We have had excellent luck with Belden 8240 (solid core) and Belden 8219 (stranded core) cabling. Carol also makes a good cable (model C1178 or C1155). There are others, but be careful. -- _______________________________________________________________________________ Charles T. Lukaszewski imp@osa.com 612 525-0000 Managing Partner & Chairman Open Systems Architects, Inc. "Who needs a disclaimer? I liked the opinions so much, I bought the company!"