sargon wrote:

On Friday, 4-November-2005 12:36, pelibali wrote:

...

Hi,

I found several unofficial values, how long can be the longest RJ45 network cable. Few sites listed about 12 meters, but I saw 20 meters and also 300ft as well; later being in fact around 90 meters

End-to-end distance from an Ethernet transmitter to an Ethernet receiver cannot exceed 100 meters (328 feet). This is due to the timing of the electrical signal on the cables.

The cable lenth has never been limited by timing. It is limited by signal degradation, which is why 10base5, 10base2 and 10baseT all have different maximum cable lengths. If timing were the issue, they'd all have similar maximum lengths, as they have similar velocity factors. If you examine the details and the reason for the timing issues, you'll realize that the maximum network distance is much greater. The timing issue is for collision detection. The ethernet standard required collision detection within 512 bit times. At 10 Mb, that equals 51.2 uS (round to 50, for convenience). So, in that 50 uS, a signal has to be able to make a round trip to the furthest point on the network, which means that the furthes point can only be 25 uS away. At the speed of light 300,000 KM/s or 300M/uS, that point is 7.5 KM away. In cables, the velocity factor is in the vicinity of 70% (light in a vacuum has a velocity factor of 100%), so the maximum distance would be around 5 KM.. That distance is far greater than can be reached with any copper cable used for ethernet. It can be reached with fibre. Also, with switched hubs and full duplex NICs, where there is no possibility of a collision, there is no maximum (realistic) network distance, though you still have to worry about signal degradation, which limits you to 100 M in twisted pair cable.

On 05/11/05, James Knott wrote:

pelibali wrote:

...

Hi,

I found several unofficial values, how long can be the longest RJ45 network cable. Few sites listed about 12 meters, but I saw 20 meters and also 300ft as well; later being in fact around 90 meters (!).

Could someone pass me please to the correct direction, where some exact (~official) theoretical/practical details are listed?!

The maximum copper cable distance is 100M. Fibre can go much further.

--

Ypu also need to make sure any bends are just that and not acute kinks. If you have to go round a corner make sure the cable takes the longest possible route to do so. i.e make it a long sweeping curve rather than a 90 degree angle. cat5(e) cable can be very easily damaged yet you wouldn't know it by looking at it. -- ============================================== I am only human, please forgive me if I make a mistake it is not deliberate. ============================================== Take care. Kevan Farmer 34 Hill Street Cheslyn Hay Staffordshire WS6 7HR

On 06/11/05, James Knott wrote:

Kevanf1 wrote:

...

On 05/11/05, James Knott wrote:

...

pelibali wrote:

...

Hi,

I found several unofficial values, how long can be the longest RJ45 network cable. Few sites listed about 12 meters, but I saw 20 meters and also 300ft as well; later being in fact around 90 meters (!).

Could someone pass me please to the correct direction, where some exact (~official) theoretical/practical details are listed?! The maximum copper cable distance is 100M. Fibre can go much further.

--

Ypu also need to make sure any bends are just that and not acute kinks. If you have to go round a corner make sure the cable takes the longest possible route to do so. i.e make it a long sweeping curve rather than a 90 degree angle. cat5(e) cable can be very easily damaged yet you wouldn't know it by looking at it.

While the above is true, it's not relevant to the question.

--

Why not? We don't know the full in's and out's of the question. We have been asked the maximum length of a network cable. Ok, but how many network cables actually run from point A to point B without any turns? Not many. So any bends really do need to be taken into account as they will cause a degradation of signal if they are not taken into account properly. It may seem silly but I have actually experienced a cable near to its theoretical maximum length that failed sending a signal. We took some rather sharp bends (not kinks or we would have changed the cable entirely) out and hey presto, full signal to a workstation. -- ============================================== I am only human, please forgive me if I make a mistake it is not deliberate. ============================================== Take care. Kevan Farmer 34 Hill Street Cheslyn Hay Staffordshire WS6 7HR

On Sunday 06 November 2005 01:56 pm, James Knott wrote:

...

...

...

Ypu also need to make sure any bends are just that and not acute kinks. If you have to go round a corner make sure the cable takes the longest possible route to do so. i.e make it a long sweeping curve rather than a 90 degree angle. cat5(e) cable can be very easily damaged yet you wouldn't know it by looking at it.

While the above is true, it's not relevant to the question.

I would consider the need to provide extra cabling around corners (an increase in length) relevant to the question regarding length.

...

Why not? We don't know the full in's and out's of the question. We have been asked the maximum length of a network cable. Ok, but how many network cables actually run from point A to point B without any turns? Not many. So any bends really do need to be taken into account as they will cause a degradation of signal if they are not taken into account properly. It may seem silly but I have actually experienced a cable near to its theoretical maximum length that failed sending a signal. We took some rather sharp bends (not kinks or we would have changed the cable entirely) out and hey presto, full signal to a workstation.

He asked distance in a general sense. Tight turns and such are installation details not maximum lengths. A properly installed cable should not affect the maximum distance.

If the OP needed the answer for a test, he now has that information and some additional information that will be of little use (and no harm) to him. If the OP is going to do something in the real world, the additional information may help. It is the additional information that makes this forum so useful. -- Louis Richards

On 07/11/05, Louis Richards wrote:

On Sunday 06 November 2005 01:56 pm, James Knott wrote:

...

...

...

...

Ypu also need to make sure any bends are just that and not acute kinks. If you have to go round a corner make sure the cable takes the longest possible route to do so. i.e make it a long sweeping curve rather than a 90 degree angle. cat5(e) cable can be very easily damaged yet you wouldn't know it by looking at it.

While the above is true, it's not relevant to the question.

I would consider the need to provide extra cabling around corners (an increase in length) relevant to the question regarding length.

...

...

Why not? We don't know the full in's and out's of the question. We have been asked the maximum length of a network cable. Ok, but how many network cables actually run from point A to point B without any turns? Not many. So any bends really do need to be taken into account as they will cause a degradation of signal if they are not taken into account properly. It may seem silly but I have actually experienced a cable near to its theoretical maximum length that failed sending a signal. We took some rather sharp bends (not kinks or we would have changed the cable entirely) out and hey presto, full signal to a workstation.

He asked distance in a general sense. Tight turns and such are installation details not maximum lengths. A properly installed cable should not affect the maximum distance.

If the OP needed the answer for a test, he now has that information and some additional information that will be of little use (and no harm) to him. If the OP is going to do something in the real world, the additional information may help.

It is the additional information that makes this forum so useful.

-- Louis Richards

--

Thank you Louis, that is the very reason I offered the 'extra' information. No offence meant to James but this thread could well crop up in a search with the searcher looking for that 'extra' bit of information. Hopefully it will be of some use to somebody :-) -- ============================================== I am only human, please forgive me if I make a mistake it is not deliberate. ============================================== Take care. Kevan Farmer 34 Hill Street Cheslyn Hay Staffordshire WS6 7HR

Hi,

On Sun, 6 Nov 2005 12:39:37 +0000 Kevanf1 <.> wrote:

...

Ypu also need to make sure any bends are just that and not acute kinks. If you have to go round a corner make sure the cable takes the longest possible route to do so. i.e make it a long sweeping curve rather than a 90 degree angle. cat5(e) cable can be very easily damaged yet you wouldn't know it by looking at it.

I don't really agree; modern cat 5 cable, if it is stranded type, is pretty durable and can stand up to a fair amount of abuse. Don't roll your chair over it too many times though. Bend radius of 10 times the cable diameter is more than sufficient. Stranded cable is used for horizontal runs, meaning outside of the wall, on the floor, behind the desk, etc. Vertical cable, the stuff that is installed in the walls and ceilings, is usually solid conductor, and is a little more fragile and vulnerable to repeated bending. So it is generally installed into place and left there, tied with tie-wraps or velcro, so it is not subject to repeated flexing.