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Coaxial  Networking Question

Posted on 2006-05-27
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Ok guys, simple question - Do i have to use a terminal resistor on each end of my 2 computer coax network, or can it loop (2 cables)?  If i boot up with only 1 cable connected and not looped i get limited or no connectivity, but with it looped i get it up fine?

I am not using terminal resistors yet
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Question by:tleighton999
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by:jhance
jhance earned 100 total points
ID: 16775000
Not exactly sure what you mean by "loop" or what exactly you mean by "coax" here but if you mean the old 10Base-2 Ethernet using 50 Ohm coax, you must have one 50 Ohm termination at each end of the cable.  It doesn't matter if the ends of the cable are at the workstation or not, the terminator must be at the end of the cable.  You connect each workstation by using a "T".  There is no termination at the "T" even though a terminator can be placed on the "outgoing" leg of the "T".

If, on the other hand, you are using some networking scheme other than 10Base-2, like perhaps TOKEN RING, then you must have a ring (is that what you mean by loop?) where the cable must go "through" each workstation on the ring, each of which have TWO connectors for the coax.
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by:tleighton999
ID: 16775088
Ok, i see - can i just buy 2 50ohm bog standard resistors and glue/solder them to the T? Would make it easier since i dont actually have much money to buy some proper ones...
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Rob Williams earned 100 total points
ID: 16775145
Use the right cable, connectors, and terminators !!
If we are talking about the most recent coax it was RG-59, used BNC connectors, and the terminators were 75 ohms. Earlier systems used other cable. You cannot solder, or even forbid glue, a resistor and expect to terminate the cable properly. You can usually get the terminators for $1 or find someone with a handful for free. As stated earlier both open ends must have a terminator to work.
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by:tleighton999
ID: 16775155
I would say hot glue is an exception :P it is brilliant for everything electrical - saves my fingers when im soldering stuff... Also comes off easily if i need it to...

The length between the two computers is less than 25cm, i am just going to bridge two netwrok connections to get internet to my other server - my school was out of cat5 to give me, so i had to make do with coax...

Rob, ill accept your answers anyway, helpful

Thank you

Tom
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by:tleighton999
ID: 16775158
Woops, Rob and  jhance, :-P thought only one person was helping me

Thank You

Tom
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by:tleighton999
ID: 16775159
Also, You can usually get the terminators for $1 or find someone with a handful for free., that might be true in the USA, but over here in the UK, all the computer shops in my city are charging over £5 for one... ripoff
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by:Rob Williams
ID: 16775214
tleighton999, please do not use a hot melt glue gun, there is a thing called connectivity <G >Hot melt glue is not a conductor, or perhaps you have different products in the UK. Also very hard to cleanly solder coax.
Coax has been dead since before the turn of the century so I know some shops are charging a lot for the connectors, here too in Canada, just because of the lack of turn-over, but I throw out a dozen I find on jobs every, couple of months. If you talk to a cable installer they may have some they have hung onto and offer them for free. Then again you never seem to find the free "stuff" when you need it.

Thanks for the points.
Cheers !
--Rob
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by:jhance
ID: 16775277
Just a note.  

I've soldered 50 Ohm resistors to the stripped end of a coax cable many times in a pinch and it works perfectly.  The lengths of the wires to the resistor are so short it doesn't have much adverse impact.  I wouldn't recommend this for long-term or commercial use since the exposed resistor is vulnerable but for home/hobby or temporary use, it's quite acceptable.

Note also: Ethernet of the 10Base2 variety is 50 Ohm usually RG-58 or similar.  The IBM Token Ring as well as the token ring scheme used by many other vendors used 75 Ohm cable.  Use RG-59 but in a pinch standard TV-type coax can be used.
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by:tleighton999
ID: 16775294
Rob, i know its not a conductor, thats why i use it for electrical stuff...

I was not planning to glue a resistor directly to the cable - the coax is already crimped with a connector on the end... I was thinking maybe put the resistor leg into the end of the T adaptor and tehn glue it in and glue the outerleg to the metal T. There would be no problems with connectivity.

And there would be no cable installers round here either :P No cable in some places over here, just Satellite TV, and ADSL over copper wires :P
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by:jhance
ID: 16775306
Just be careful soldering to the "T".  This is a fairly large piece of metal and the inside stuff contains plastic.  If you heat it too hot the internal insulator will melt rendering it useless.  I usually get a BNC connector, which is fairly low priced and solder one leg of the resistor to its inner pin and then solder the other end to the outside of its body.
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by:Rob Williams
ID: 16775309
tleighton999,
As a fellow member of the commonwealth, send a mailing address to my e-mail (click on RobWill) and I'll mail you a couple. Seriously. I'm sure they will take a while to get there, but you will have it properly installed in the end. In the mean time you can make do with glue & solder. <G>
--Rob
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by:tleighton999
ID: 16775331
Hehe, more glue than solder i think - and im trying to make do with a soldering iron to melt the glue as someone, *not mentioning my dog* decided to chew up the cable into the gun and the trigger. So its completely useless :D

Tom

Rob, sent you an email - if you get a message back from AOL Postmaster, tell me and ill give you another email address, AOL servers are so picky sometimes
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by:Rob Williams
ID: 16775356
Hot melt glue and a soldering iron, now there is a mess  <G>
Sent a reply to your e-mail. Let me know if you don't get it, or if you do reply with address. (don't post address here)
--Rob
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by:tleighton999
ID: 16775434
Yuppy, and as soon as you try sticking a Heatsink and Fan to a mobo with it when you have broken the processor socket clip to clip it on with - and then go play a game of Americas Army on it, it gets real messy :P
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