Long cable runs, multi-core or single cables?

[Arpangel]

I think it's a hobby he gets paid for but not sure. He's a nice guy, (only met him once mind you) I can try to get his number or email if you like, I'm sure he'd be happy to chat.

That would be great Sam.

Thanks!

[ef37a]

I live in the 'home' of model railway and as a young man would marvel at the engines in Basset-Lowkes windows.

I did my day release electronics at Npton Technical College St Georges avenue. On the lower levels were some stunning, working scale models. One that really impressed was a marine engine, huge thing in reality.
I wonder if they are still there? Built by a chap called Watts.

Dave.

[Sam Spoons]

Andy pointed me at Chris' web site.

http://www.timpdon.co.uk/timpdon/timpdonmodels.htm

Chris probably won't remember me (and certainly won't know me as SS) but if he does it'll be as Andy's mate Chas

[Arpangel]

Andy pointed me at Chris' web site.

http://www.timpdon.co.uk/timpdon/timpdonmodels.htm

Chris probably won't remember me (and certainly won't know me as SS) but if he does it'll be as Andy's mate Chas

Thanks a lot Sam, much appreciated, looks like he does 45mm scale too!

[wireman]

There will definitely be crosstalk between pairs using CATx cable though not a serious amount depending on what you do.

Some crude tests I did a few years ago on cabling around my house showed that a 0dBu signal would produce about -50dB in another pair. Audible in some situations but prbably not a problem in most? Not mixing line levels and mic levels would avoid virtually any crosstalk anyway.

Dave.

Perhaps SOS could do some testing of this. It seems that some of these cables are supposed to have varying twist rates to combat crosstalk but of course their focus is high-speed digial signals and not audio.

[Sam Spoons]

IIRTC the spec for Cat5/6 requires specific twist pitches which, as you say, are different for each pair so, in theory, they all should.

[ef37a]

There will definitely be crosstalk between pairs using CATx cable though not a serious amount depending on what you do.

Some crude tests I did a few years ago on cabling around my house showed that a 0dBu signal would produce about -50dB in another pair. Audible in some situations but prbably not a problem in most? Not mixing line levels and mic levels would avoid virtually any crosstalk anyway.

Dave.

Perhaps SOS could do some testing of this. It seems that some of these cables are supposed to have varying twist rates to combat crosstalk but of course their focus is high-speed digial signals and not audio.

Yes, the twists are staggered, one consequence of which is you need to be careful what you send down them as signals arrive at very tiny different times which can be a problem with say video sources?

One way to greatly reduce cross talk is to use a very low driving resistance. Op amps can easily be configured as 'zero impedance' sources.

I am not sure SoS would consider it part of their brief to test CAT cables? Maybe as a bi product of a review of the XLR boxes if they ever came up for review?

Dave.

[ef37a]

IIRTC the spec for Cat5/6 requires specific twist pitches which, as you say, are different for each pair so, in theory, they all should.

Absolutely! When the network firm I worked for started a new product some poor sod had the job of cutting out a precise length of the new cable and counting the twists!

Not I tho'but.

Dave.

[Sam Spoons]

Not too bad if it was a few inches but less fun if it was a few metres

Poor Sod "Three hundred and 11, three hundred and 12"

Doris (the tea lady) "Do you want a cuppa dear?"

Poor Sod "Bugger....... One, two, three"

[wireman]

IIRTC the spec for Cat5/6 requires specific twist pitches which, as you say, are different for each pair so, in theory, they all should.

Do you have a reference for this, the reason I ask is the following blog which I looked at before posting earlier...

https://community.cedia.net/blogs/david-meyer/2019/09/16/category-cable-twist-rate

[Sam Spoons]

Sorry no, it's just one of those things that we "know" to be true*...... Reading your link it appears that twist rates are not specified but are the choice of the designer. What your link does say is that the minimum performance is in the specification.

Interesting read, I got my info from an old mate who worked in the field so it's entirely possible that it got slightly scrambled in translation.

* i.e. 'think we know'

[shufflebeat]

This isn't the Dave Rat vid I referred to earlier but it's relevant to the topic:

https://youtu.be/gGgPDEz5sNU

Looks like DR's been hitting the eye-liner. Boredom does strange things to all of us.

This looks pretty convincing to me but I don't really have the Latin to critique it properly. If anyone fancies casting an edjicated eye over it I'd be interested to hear opinions.