[AusNOG] 700Mbps over copper pair...over 400 metres

[Tim McCullagh]

----- Original Message ----- 
From: "Kai" <vk6ksj at westnet.com.au>

>
> I'm guessing that was tested on "perfect copper" at 400 metres,
> and not the stuff that's sitting in the pits and up the columns around 
> Aus,

I would hazard a guess that it would have been tested on a test bed similar 
to what is installed in Australia.  Much of the copper in AU is in good 
condition.  It is some of the design, install and maintenance practices that 
cause the problems.  I have tested cable at new, 15 years of age and 25 
years of age and the cable generally doesn't deteriorate.  It is the ingress 
of water into joints, and where external factors have damaged the cable at 
the time of installation or some time after which are not repaired 
correctly, that causes most of the problems.  The same install issues that 
affect Cat5 /6 installs also affect cat 3 cables and it is such issues that 
generally cause the faults in later years.  In fact in aerial cable 
installations, we found that the replacement of joints on cable at 25 years 
of age took the fault performance of the cable back to new cable rates, 
except where the cable had either fire, bird or mechanical damage pre 
existing.  This put the perfect copper rubbish to bed many years ago.

The idea of new cable being different to old cable because of age is 
misguided, and shows a lack of technical understanding.

> dealing with constant temperature and humidity variations,

Again this shows a lack of technical understanding, buried cables have a 
reasonably narrow temperature range.  The ground is an insulator and narrows 
the temperature range variation.

Humidity unless the cable is aerial cable and is install in the old aerial 
cable boxes, then humidity should have no influence what so ever.  The 
copper is insulated inside an external sheath.  What happens is the joints 
either by design or poor maintenance practices may fill with water or 
condensation.  You need to either fix the seal or replace the joint not all 
the copper to fix this.  Or it may be due to third part damage that wasn't 
repaired correctly. We have all seen the plastic bags on temporary joints. 
The question is, "is it the copper or the bloody idiot that damaged it that 
we should be blaming?"

> at various stages of decay

Only if it is not maintained properly

>and after being repatched and respliced a few hundred times.

Copper is not patched and spliced.  Copper is jumpered and soldered or uses 
insulation displacement methods in climatically controlled environements 
like exchanges, pillars and cabinets.

As for resplicing, copper is jointed using connectors which displace the 
insulation that also have a sealing grease. They are never reused, they are 
replaced.

My apologise in advance for any offence caused, but lists such as this one 
would be of more useful if posters either took the time to research what 
they say or limited their posts to things they do know about.  The first 2 
paragraphs of this post were good and of interest, it is a pity the last 
paragragh was written.  We all need to remember that some people who read 
the posts may not be able to distinguish between the good stuff and the 
crap. Then we hear people repeat the rubbish time and time again because 
they saw it on a technical list and thought it to be fact, until it becomes 
accepted as fact.  Once it becomes accepted as fact then it is difficult to 
undo.

regards

Tim