> From: James Miller <[EMAIL PROTECTED]> > Subject: Re: newbie networker, old-timey networking parts query > > On Sun, 29 Jun 2003, Ben A L Jemmett wrote: > > > > I'm not sure if a balun would help; they're available with RJ45 > on one side > > and BNC the other, and I think they're suitable for Ethernet. My > first > > Wouldn't that be the cat's meow? Physically they look ideal: rj45 > jack on one end, bnc male coupling on the other. And they're small > and not too expensive (in the $5 range). But the thing that > confuses me is that there are other things advertised to convert > 10 base2 to 10 baseT for 10 to 20 times the cost. Here's an > example, snipped from the 'net:
[ example snipped ] I've never quite understood why the networking industry chose to forego the huge bandwidth advantages of coax for the twisted-pair varieties - except, of course, to boost profits from cheaper materials. The twisted-pair stuff uses "current-mode" amplifiers, which aren't well suited to either simplex signaling (where signals travel both directions in single coax or a pair) or the occasional "collision". Thus, most of the current windoze-style products use two pairs - one for output, one for input: they use duplex transmission. The balun devices just combine them (via transformer) into the single, simplex, coax connection. The network cards must then either be able to detect/correct collisions, or to setup for simplex (versus duplex) transmisions. In a windoze world, where the user isn't permitted to know anything about what their hardware is doing, it is becoming increasingly harder to change the hardware settings from the defaults which either mickeysoft or the computer manufacturer desire. (And I'm sure that in at least some cases, the cheap net cards or motherboard-based networking CAN'T be changed!) It's one way for the manufacturer to claim his equipment is "twice as fast" (duplex) as other methods (simplex). In reality, the coax often has a hundred times the possible bandwidth compared to twisted pairs - but the chips on each end are the limiting factor. Bottom line: RJ-to-coax baluns work fine, if your system can be set up to do simplex, rather than duplex data transmission. (And they are CHEAP! There's nothing in them but a core with a few turns of wire passing through the middle; profitably sold for $5 or less each. Some are even more cheaply made, laying out the "transformer coils" onto a flat PC board - but just as effective, if not as sturdy.) __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com To unsubscribe from SURVPC send a message to [EMAIL PROTECTED] with unsubscribe SURVPC in the body of the message. Also, trim this footer from any quoted replies. More info can be found at; http://www.softcon.com/archives/SURVPC.html
