Safeguarding radius when installing cables

[Anthony-C]

Hi All

I'd like some practical tips for routing cables in ways that preserve bend radius when installing data (Cat5e) and aerial cables.

I've a feeling this isn't the way to do it! -
http://www.pcstats.com/articleview.cfm?articleid=153&page=3

Thanks in advance.

 

[timbim]

Well they've clearly never heard of IDC punchdowns...

But what a genuinely naff job they ended up doing!

 

[Alarm]

Rough as Fluck.

 

[Anthony-C]

That's agreed then... but I'm glad they posted their pics as I've yet to find any better examples.

Should cables enter walls at 45 degrees instead of 90? Can you get minimum radius cable guide brackets?

I figure you could cross a sharp corner between walls by curving a cable to run along the corner and out onto the other wall in an S shape but that takes a lot of space... What do the pros do?

 

[Alarm]

In what situations?>
Domestic, commercial?

Commercial you should be able to access points and use trays ( should).
Domestic is common sence.
Run conduit where possible and send thru that. Some copex helps on messy bends.

 

[ban-all-sheds]

http://www.pcstats.com/articleview.cfm?articleid=153&page=3[/QUOTE]
Care in the community just isn't working, is it....

 

[holmslaw]

..

 

[JohnW2]

I've a feeling this isn't the way to do it! -
http://www.pcstats.com/articleview.cfm?articleid=153&page=3[/QUOTE]
Indeed - and my attention was captured by:

The best way I've found to attach a bare copper wire to a screw-in connector is either to wrap the wire around the screw in a counterclockwise direction .... will ensure that as the screw is tightened it pulls the wire in tightly

It seems that either they have a very confusing way of expressing themselves (i.e. are talking about taking the screw right out and looking at it from the thread end) or else they must have found accessories with left-handed screw threads!

Kind Regards, John

 

[JohnW2]

...and I forgot to add. Whilst I can see that it may be of at least theoretical importance with some aerial cables, I find it rather hard to believe that bending radius is a significant issue in relation to cat5e cable.

Kind Regards, John.

 

[DetlefSchmitz]

Apparently it's easy to change the characteristic impedance at the bend, and, by introducing reflections, completely wreck the transmission characteristics. Result, slow throughput.

 

[JohnW2]

Apparently it's easy to change the characteristic impedance at the bend, and, by introducing reflections, completely wreck the transmission characteristics. Result, slow throughput.

That would obviously be the theoretical risk, particularly with 'transmission lines' like coax, where the geometry is important to the characteristic impedance. I was just expressing my surprise/doubts that it would prove to be a significant issue in practice for cat5e cable. However, perhaps I'm wrong, particularly as we push the transmission speeds we're trying to achieve.

Kind Regards, John.

 

[Anthony-C]

It does depend what the Cat5e cable is used for but bends matter for gigabit. The usual reason given is that tight bends straigten out the twist in the pairs and reduce noise rejection, but at those speeds the cable is also very much a transmission line. If your Cat5e isn't quite up to gigabit the interfaces will helpfully negotiate one tenth the speed instead.

At home I need to run both Cat5e and WF100 aerial cable out through a cavity wall at ground floor level. Presumably that's best drilled from the inside at a downward angle to reduce water bridging.

Where the cables emerge they'll need some sort of protection against kinking when the cycles are leant against them (sigh). The minimum radius for WF100 is 65mm, like wrapping it around a jug kettle - that curve will just fit in flat angled trunking ~27mm wide, but emerging from a hole in a brick wouldn't it need steel trunking 70 x 70? Think I'm suffering common sense fatigue 'coz I haven't noticed many houses fitted with that...

 

[ban-all-sheds]

http://www.pcstats.com/articleview.cfm?articleid=153&page=3[/QUOTE]
Against stupidity the Gods themselves contend in vain.

 

[bernardgreen]

The minimum bend radius I have for WF100 is 40mm but it does vary depending on the manufacturer ( Belden type H125 is 40mm )

Drilling the hole with a steep slope will reduce the amount of bend required at the ends of the holes and by cutting a slot below the hole much of the bend can be in the brick. Don't forget to take the cable down wards from the hole for an inch or so and then do a 180 degree bend to go up the wall to allow water to driop from the cable and not into the hole in the brick.

 

[JohnW2]

It does depend what the Cat5e cable is used for but bends matter for gigabit. The usual reason given is that tight bends straigten out the twist in the pairs and reduce noise rejection, but at those speeds the cable is also very much a transmission line. If your Cat5e isn't quite up to gigabit the interfaces will helpfully negotiate one tenth the speed instead.

That makes sense; although (pretty long) cat5e cables in my house have been installed without any consideration of such niceties, and work fine, I am not trying to get gigabit speeds.

I've been trying to interrogate my 'intuition' which led me to suggest that bending radius might not, in practice, be much of an issue with cat5e cables, and I think my subconscious considerations probably included at least three things. Firstly,as above, I have no experience of attempting to use these cables at very high speed. Secondly, I was probably thinking that any problems (of reflection or reduced common-mode rejection) due to tight bends would probably fade into insignificance in comparison with what happened when the cable hit terminsals (such as we have seen) and connectors etc. Thirdly, I was probably also thinking that what was a pretty tight bend (in relation to the radius) of the cable as a whole would represent a much less severe bend (again, in relation to radius) for the relatrively tiny conductors contained within the cable. However, I accept that all of those thought processes may well be flawed, and that there may be a need to install carefully if one wants very high speeds.

In terms of the discussions about installation, the steeper the angle you go through the wall, the less of a bend would there need to be on each side of the wall, hence the easier would it be to loose some (maybe even all) of the bend within brickwork (or whatever).

Kind Regards, John.