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Why is cable length an issue with AirLink+ router?

Posted on 2005-04-16
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Last Modified: 2013-11-29
My friend has an AirLink+ AR315W wireless 802.11g router.  He finds that whenever the cable is longer than 14 feet, the router and his computer stop communicating.  He tested the cable with a contiunity tester, and it tested fine.  He tells me he uses "category 6" cables.  He needs to make a 200 feet connection.  (The wireless capability seems to be nil, but he's not concerned about that; he primarily wants physical connections to his various computers around the house.)

Anyone knows what's going on?

Thanks.
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Question by:Niemand
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by:rindi
ID: 13800067
14 Feet is nothing and shouldn't be an issue. The link provides the techniacl max cable length:

http://www.duxcw.com/faq/network/cablng.htm

Did your friend make the cable himself? Maybe he used the wrong wires for the wrong connection (they should always be in pairs, as 2 wires are always twisted amongst each other to reduce noise).
I'd still think there's something wrong with the cable. Get a new one and try it out. Also try connecting it to a different port. On the PC which you have connected to the router make sure the NIC is set to autonegotiate the speed and the duplex mode (These settings should always correspond the other side's settings. As the router's port probably can't be set to a certain value and itself is set to auto, the nic should also be on auto.).
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by:GinEric
ID: 13800256
What modem, and did he use the phone wire supplied with the modem?  Or is he trying to use a flat telephone cord?

Check that first.
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by:neteducation
ID: 13800266
I agree that 14 feet should not be a problem at all.... however when you are saying that the wireless capability is nil, then this could be because of strong electromagnetic fields around, which could be a problem for wired communication too. As he is using Cat6 the cables themself should be fine... however if the is such a strong electromagnettic field around, you can try using shielded cables (STP) instead of unshielded (UTP) cables
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by:GinEric
ID: 13800275
You might want to read the box before buying an 802.11g

"Several new, incompatible protocols are in the process of being released, including 802.11a (54 Mbps over the 5 GHz band), 802.11g (22 Mbps over 2.4 GHz), and Texas Instruments' PBCC 22 Mbps standard."

http://www-ee.uta.edu/wirelessnetworking/OPNETwebpage.htm

802.11g doesn't work with everything.
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by:pseudocyber
ID: 13804848
Could be a bad NIC on one end - isn't generating enough power to reach the other end of the cable.  If a new cable doesn't fix it, check the NICs - in the computer and on the switch/hub.
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by:GinEric
ID: 13804965
I'm pretty sure his friend is using a flat telephone cord.  The wireless is probably disabled within the router too.

No reason for these not to work.  The electromagnetic field would have to be pretty strong, on the level of a nuclear accelerator to interfere with a twisted pair and CAT6.

J. Presper Eckert "The magnetic field varies as the inverse of the cube of the distance."
I think he got that from Maxwell or Kepler's Laws, but someone asked him about a truck with a big magnet on it, passing by their company and would it erase Univac's data; he gave the same answer, adding that the truck couldn't carry a magnet big enough.

The guy must have a pretty big house too, 200 foot connection!

:|
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by:rindi
ID: 13805002
I'd tell him to buy a network cable (not telefone cable, they aren't always connected properly, aren't shielded and might not even be twisted pair, or if he connected the connectors himself, check for errors in the connections. I'm sure this is a cable issue.
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by:neteducation
ID: 13805070
See original question... he is using a category 6 cable.. so this shouldnt be it.
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by:pseudocyber
ID: 13805084
Did he MAKE the cable or BUY the cable?  When I say cable, I mean the connectors too.  If he made them, it could be that the wiring is working, but incorrect.  For instance, if you put the colors, in "color order" on both ends, this will cause a "split pair" condition which will work, but not well.  Or there could be a bad crimp, or two.
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by:rindi
ID: 13805100
But still, do you know if he made the connections himself or if that cable is still OK? This is typical behaviour for bad cable or bad connectors, so try another cable which was bought finished (no self made cable). He can allways make his own cable later when he knows definitely that the rest is OK.
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by:GinEric
ID: 13805370
"See original question... he is using a category 6 cable.. so this shouldnt be it."

Yeah, but what is from the wall outlet to the DSL modem, if that's what he's using.  Or are you using a DSLAM or other ATM Switch?

If it's a modem, then the cord from the wall outlet to the modem has to be twisted pair, the one supplied by the ISP usually.

14 feet is just about where a flat old telephone cord fails for high bandwidth.

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by:neteducation
ID: 13805660
Gin: Come on... I don't want to word-fight here, but it looks to me as if your primary goal is to make myself prove wrong. Let's try to focus on solving the problem, not on "I know it better than you".

From original Question> the router and his computer stop communicating

If the router and the computer stop communicating then this has nothing to do with the connection from the wall-outlets to the dsl-modem.
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by:pseudocyber
ID: 13805704
>>He finds that whenever the cable is longer than 14 feet, the router and his computer stop communicating.  He tested the cable with a contiunity tester, and it tested fine.  He tells me he uses "category 6" cables.  He needs to make a 200 feet connection

If he's "making" the cables himself, I would bet it's a problem with pin out or the quality of the crimped on connectors.

If it's a factory made cable, I would lean towards an interface problem or perhaps environmental (some kind of interference).
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Author Comment

by:Niemand
ID: 13851998
Thanks for all your replies.  The cable from the wall to the DSL modem is the one provided by the DSL service provider.  The cable my friend is trying to make is for connecting the DSL modem to the computer ethernet connector.  

He says he is using the best quality crimps he can buy and crimping them as well as he can.  He says that the 14-feet cable he created works fine.  Then he created another one in the exact same way except that the cable this time is 200-feet long, and it fails.  His multimeter shows good continuity from conductor-to-conductor at the two ends and very, very low resistence.

 Please keep in mind that we are talking about the wired connection between the hosts here; he is not concerned with the wireless feature.  He doesn't see any possible source of interference in the area where he lives.

He will try to come by and show me what he's done, and perhaps I'll be able to convey more detail.
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by:GinEric
ID: 13854042
Did he try to make an interim size, like 30 feet?  This is cheaper than 200 foot runs to see if it works after 14 feet.

Crimping is an art form.

All of the wires must be correctly crimped according to a standard color configuration [the easiest way].  The pairs must remain twisted right up to the crimp, which usually means stripping the ends and trimming to somewhere between 1/8in and 3/16in.  The wires should then be "flayed" out like a flat ribbon that fits exactly into the connector, with no excess untwisted wires outside the connector, the bare copper fitting exactly into the slots with no excess outside of the crimp slots, and held firmly in place while making the crimp.

Most people get the order of the blue/white and green/white mixed up, because the colors are usually very faded looking.  The color code can be found at most UK university sites as well as the order they should be in on both ends.

See if he can get a 30 foot one to work, if not, he's doing something wrong.  He may have gotten the first on right, the fourteen foot one, but thereafter got the wires out of order.  This happens a lot, like I said, with the blue/white and green/white pairs.
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by:neteducation
ID: 13854126
I basically agree with my "pre-writers" in saying that crimping at real good quality is not that easy. And I would not dare calling a self-crimped cable category-6, because its most probably only Category-6 "on the way", but not at the ends.

To see if the cable is really at the quality needed, what he needs is a cable-tester that can test for category-5 or category-6-compatibility. Testing it with only a multimeter will show you good continuity and a low resistance even for a telephone-cable (which as far as I remember needs to be category 2 or 3 two work for telephony). The problem with big length is more that (as described by GinEric) the right cables are twisted and that cables are actually twisted.

I think the best tip we can give is to have him buy a factory-made cable at that lenght. They are not that expensive, around $30 at the first yahoo-store I found (http://www.store.yahoo.com/ktusasys/cat6cable.html), however depends of course where you live... (here in Switzerland you'd probably pay around $50... but I know everything is expensive here)

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by:pseudocyber
ID: 13857335
I bet the colors are wrong.  Continuity would be fine, but if he's got split pairs, this will cause a problem at longer lengths than shorter.
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by:GinEric
ID: 13863599
This may be somewhat of an embarassment to those who sell such cables, but I was able to get 200 foot length cables, already crimped with connectors, from a local computer store for $5.00 each.

I think the Oriental owner simply wanted to get rid of them, or, he wanted to get a new customer.

One thing to comment on:

"The cable from the wall to the DSL modem is the one provided by the DSL service provider.  The cable my friend is trying to make is for connecting the DSL modem to the computer ethernet connector."

If he is going directly from the modem to a NIC on a PC, there actually could be a problem with the DSL modem's ability to drive the signal.  You wouldn't think so, I suppose, but don't forget that a modem, even with DHCP routing, is not quite a router, like one with 5 ports and one auto-in port.  Had it been such a beefier router, I would discount the router, but the DSL modem is manufactured at the cheapest level possible and usually supplied free by the ISP simply to connect from wall to modem, and thereafter one Ethernet output connection to either a PC or router.  I would definitely suggest either get the DSL modem in the same room as the first ethernet conncection [PC or router], and thereafter run the longer length cable(s).  In fact, with a DSL modem, router, and server PC, I would place all three in the same room, and then output the router to other computers around the house.

T568A, while the preferred premisis wiring, defers to mass produced T568B; there was a reason for the difference at one time, and the standards that preceeded it from the original ethernet design topology, having to to do with an employee [telephone repairman] being able to simply look at the colors and tell what circuit it was on, but that seems to have changed.

Most store boughts may be T568B, but A was the original and you'll still see supplied with telephone equipment.  B, or the Orange pair first, meant that there were two separate networks on the premisis, while A meant that there was only one.  Making the troubleshooting and repair job faster and easier.  Besides, at least one site has the crossover listed as A/B, which may be, but seems dubious at best.  If you were to follow this site's definitions:

http://www.incentre.net/incentre/frame/ethernet.html

You would quickly find out that it fails for a lot of "Ethernet devices," particularly those that have autosensing and cascadeable routers, depending on where you put the cables.

Whichever he uses, it is a good idea to fully know and have some good pictures of the actual connectors, face on, tabs up, when crimping.

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by:pseudocyber
ID: 13865349
Tab goes down when determining color.  Pin 1 is on the left.

568A:

1 White with Green
2 Green with White
3 White w/orange
4 Blue with White
5 White with Blue
6 Orange with White
7 White with Brown
8 Brown with White

568B:
1 White w/orange
2 Orange with White
3 White with Green
4 Blue with White
5 White with Blue
6 Green with White
7 White with Brown
8 Brown with White

A 568A on one end and a 568B on the other = Crossover cable.

T568A is preferred termination in residential structured cabling because it has Blues & Oranges (first two colors in the telephone system of coloring) in the middle of the jack.  Blue is Pair 1, Orange is Pair 2 all on pins 3-6 and is compatiable with the older USOC system.


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by:GinEric
ID: 13873349
"Tab goes down when determining color.  Pin 1 is on the left."

Facing away from you, tab down.  It is also Pin 1 on the left, tabs up, facing you.

I used to have exact photographs that showed the various views, as an engineering blueprint or diagram would show.  I looked though about 1,000 sites and can't find a single picture that shows an actual RJ-45 CAT5 connector with wires in place in face view and above view.  You'd think someone would realise that all those explanations can be shown in only eight photographs.

Add four more for the crossovers.

And maybe a couple showing how the ends are properly stripped and flayed out, then trimmed to the same length in one cut across all eight wire leads.  As I said, somewhere between 1/8 inch and 3/16 inch.

Neat, precision cut, flayed out to form a flat ribbon effect for ease of insertion into the connector before crimping, and the final product should be a perfectly crimped cable end.

All the extra stuff on the pages you find is really a waste of time without an actual showing of the components, the process, and the results.

When everyone is using the document from yoda.uvi.edu [you know mon, de university of Jamaica, made by Yoda while he was using his pipe mon . . .] you can see, I guess, why no one has photographed the actuality yet, the Force, apparently, was not with Yoda on that day.

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Author Comment

by:Niemand
ID: 13892063
GinEric,

I believe his setup is as follows:

wall ---> DSL Modem ---> AirLink Router ---> AirLink Switch ---> computer

He told me that the swith was also made by AirLink, model ASW105/A3, a 5-port 10/100.
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Author Comment

by:Niemand
ID: 13907393
This is what my friend tells me (in quotes):

His set up is:
wall ---> DSL Modem ---> AirLink Router ---> 200-ft cat6 cable ---> computer (he removed the switch to ease problem-solving).

"I tried 200 ft, 100 ft, 50 ft and 25 ft.  None of them worked. The only time it worked was when it is less than 15 ft. At 15 ft, Window XP a local network connection, but Internet Explorer browser does not work until the cable was shortened to 14 ft."

"I cut the cat6 cable and clamped them just like how anyone can get them at an electronic shop.  There are four sets of color in the cat6 wires.  Each set has one wire that has a white line on it.  They are all twisted all the way to the connector with no excess outside."

"My room has two phone lines out of one wall outlet.  The phone worker put a Y-connector to the wall, and inside of the Y connector are for wires to the wall--two of those wires go to the phone, and the other two wires go to the DSL.  Everything is in the same room.  I will try to get a new DSL modem form an electronics shop.  Maybe my free DSL modem from AT&T doesn't have the power to go all 200 ft."


To pseudocyber:

"I have acat6 500mhz cable with blue PVC jacket 24awg unshielded twisted pair.  The twisted pair are blue & white with blue line, orange & white with orange line, green & white with green line, brown & white with brown line.
 
I set it up this way , am I wrong?
 
plug side a
1 orange
2 white with orange line
3 blue
4 white with blue line
5 green
6 white with green line
7 brown
8 white with brown line
 
plug side b
1 orange
2 white with orange line
3 blue
4 white with blue line
5 green
6 white with green line
7 brown
8 white with brown line"

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Accepted Solution

by:
pseudocyber earned 200 total points
ID: 13907913
Yes, it's wrong.  It should be:

1 white with orange
2 orange
3 white with green
4 blue
5 white with blue
6 green
7 white with brown
8 brown.

The way you did it called a split pair.  You've got a signal travelling over two different pairs, the blue and the green.  Blue should not be involved at all with 10/100baseT.
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by:GinEric
ID: 13910536
Pseudocyber has got it.  The two centermost pairs are used, they are basically "enclosed," that is, the blue/blue white, lies inside of the green/green white pair.  What you did was to "separate" or split them.

It's a wonder, but like any phone line with one open wire, it will work for short distances.

It's the most common mistake in wiring, so don't feel bad.  Try it the way pseudocyber stated and tell us if it now works.
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Author Comment

by:Niemand
ID: 13923922
It's working very well now at 100 ft.  My friend will try 200-ft come Sunday.  Thanks to everyone, especially GinEric and pseudocyber.
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by:pseudocyber
ID: 13925405
You're welcome. :)
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Author Comment

by:Niemand
ID: 14001350
Update:

My friend now has got a cable running from one house to the next, and he tells me it's transmitting extremely well.  He is very impressed with the transmission.  He says the shielded cat6 performs the best, and that an unshielded cat6 is practically equivalent in performance to a shielded cat5 cable.

Thanks again.

Question:
pseudocyber, why the difference in wiring colors between your post on 4/26 and what my friend's cable has (as posted on 5/2)? Aren't the colors standard on this type of cable?
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