125M : Exposed VM coax cable in junction box

[Coffeeguy]

When I had a repull done, the old cable was left exposed in the junction box out front and I've connected back to this to confirm it is still live (albeit an increase of 5~ dBmV increase on downstream power level). What are the ramifications on the network of the live and exposed coax cable in the junction box if any at all and should I report this to VM?

[RB2004]

It will introduce noise onto the network and create a signal leak.

If its still connected put one of these F couplers on it

http://www.worldvu.net/au/products_images/F_Connector_Joint.jpg

Which can be purchased here,

http://www.ebay.co.uk/sch/i.html?_nkw=F+coupler&_sacat=293&_odkw=F+connector &_osacat=293

Then cap it off with one of these F terminators

http://www.ebay.co.uk/sch/Sound-Vision-/293/i.html?_nkw=F+terminator

Can try reporting to vm but the chances of them actually doing something themselves might
Not be too great as their general attitude is your services are working, there is no fault so it doesn't justify a service tech visit.. It's more networks who are concerned about this kind of thing but I understand that networks can only be called to visit by a tech, not the support staff.

Make sure everything is tight just a little more than hand tight using a spanner when you carry out the termination then everything will be good

[babis3g]

same here, may get a small pack from ebay
When they done cable repull they left the old cable live and with out terminator
Still the same condition till now

[Coffeeguy]

Thanks RB2004. I'll probably do that and terminate the live cable properly. Would it make any difference if the live cable was indoors at room temperature or would it need terminating the same way?

[ferretuk]

Originally Posted by Coffeeguy

When I had a repull done, the old cable was left exposed in the junction box out front and I've connected back to this to confirm it is still live (albeit an increase of 5~ dBmV increase on downstream power level). What are the ramifications on the network of the live and exposed coax cable in the junction box if any at all and should I report this to VM?

Don't touch and report it to VM - It's their network and you shouldn't be playing with it! What made you 'look' to see if the old cable was live?

If the network is affected it's up to them to fix it, at their cost, and you sticking a termination on it may actually make things worse depending on if the term is truly 75R or not...

[RB2004]

How can it make things worse.. For one thing you are shielding the centre core which will if nothing else get rid of any noise introduction.

I've had to sort out my cabling at home loads of times because of the incompetence of some engineers.. Stress the word "some"

If done properly using proper equipment it will not adversely effect the network... But I'm not completely defending DIY modifications as I've posted several times about people using dual shielded cable and twist on connectors instead of triple shielded cable with VM approved PPC EX6 connectors. It's about how you do it.

Best thing to do is phone it in, if they don't do anything then do yourself if you are worried. But I wouldnt hold any hope as its more of a networks thing, and if your services arent actually broke they might not want to know.

But it only needs a coupler and a terminator.

Don't mess with connectors as if done incorrectly that will make things worse only use the coupler and terminator if an F connector is already present and make sure that all connections are tight

Doesn't matter if indoors or outdoors no coax end should be left unterminated.. Same strictly speaking applied to tv aerial points as well especially with freeview.

But sometimes unfortunately you have to undertake things yourself to improve your own services.. I'm not saying its right or encouraging improper methods but I had to have 6 engineers out over 6 years.. Eventually enough was enough and I purchased my own equipment which i must stress was identical to what vm use and not 3rd party equipment..and did it myself.. I noticed improved services and the standard of my install was also higher.

When I had a cable repul done I even had to dig and bury the cable myself just to ensure it was done to a proper depth.. Much to the annoyance of the team who turned up few days later to bury the cable.. But they as much admitted to my face they was only going to bury it a few inches.. Which is stupid, so I turned them away, but if I have a cable buried on my lawn i want a cable that is buried to the same regulations as any other cable so it does not get accidentally damaged, which in turn will adversely effect my services.

With these couplers and terminators it's only a few £.

It cost me well over £50 to sort out my services.

Afterwards i got an apology and agreement of vm that I should not of had to sort out my services myself and that how it is now should of been how it was in the first place and they refunded my 1st TiVo box activation.

But as with anything you get people who care about their work and do best job possible and another who does the bare minimum just to get to next job.. And some engineers take view even if not perfect they will rather leave as is to save time than spend time putting it right.

As realistically if they was doing their job properly it should never of been left connected.. If you take it even further ideally the old cable shouldnt even really be left in the ground either.. But truth is though, they put the new cable in and probably didn't know which cable was the old one.. So to save disconnecting wrong person left it connected. But it takes up a useable port on the tap that another new customer might need in future and space in the ducts which in some places is already limited. Which is probably how in some areas some tap ports end up with splitters put on them.

Do stress that in all cases it is "some"

Not all.

[ferretuk]

Originally Posted by RB2004

How can it make things worse.. For one thing you are shielding the centre core which will if nothing else get rid of any noise introduction.

Suggest some research on transmission lines, impedance matching and reflections...

[RB2004]

Originally Posted by ferretuk

Suggest some research on transmission lines, impedance matching and reflections...

Good idea, here's the feedback page for vm.

http://www.virginmedia.com/information/homepage-2011-feedback.php?vmsrc=vmfeaturepage

Then maybe their installers, contractors and service techs who are presently doing this.. Again not all, will stop leaving unterminated cables in the first place if they are better educated... And joining cables that are too short rather than cutting a new cable. As on oscilloscope that also introduces reflections.

Hopefully on the advice of your feedback will will start demonstrating these effects to engineers with an oscilloscope during training and the effects of unterminated connections.

They are still going around using wrong power supplies on the superhub after over a year of complaints from people about being left with wrong
Psu that's how competent some are.. That they stick a 1amp transformer on a device that requires a 1.5 amp transformer.

Might be worth telling them that as well.

[Coffeeguy]

Thanks RB2004, your advice is invaluable. I have been having on and off T3 timeouts since the repull (9 months ago) with all levels being in range and VM CS are non the wiser. I started at the modem and have gone through the run of cable to find any point of failure which lead me to the junction box.

The repull (if that's what you want to call it) was a botched job itself. Instead of lifting 2 small concrete slabs in my front garden, the two guys drilled a hole in my wall and cemented the new cable to the side of my garden wall(!!). They then stripped down the one side of the newly install twin cable at the junction box and put an F connector on the other side. Couldn't they have used single cable instead?

I've connected back the old cable which was still live at the junction box and will terminate the new installed cable when the terminators arrive and will see if there's any improvements.

[RB2004]

Hi what are your levels currently?
What was their reason for the repull? Is the newer cable thicker? They call it RG11, normal thickness is RG6.

Seems to me like because your signal levels on old cable have increased by 5db that.. If the new cable was thicker they installed it to give you a better signal, then in the meantime at some point the problem causing low signal levels was fixed, maybe the tap was changed or amp problem.

This then lead to upstream being too low causing the t3 errors.

Just guessing though.

But if you could post your current signal levels we can check for you if they are ok on the old cable.

I know, you would think you can trust vm staff but some you can't. On here there's really knowledgeable engineers who do things properly but round here they don't, that's why I got fed up.

6 years I put up with being told I had signal problems, what's worse is they lied to me as well.

Does sound botched but not surprising, was funny when I had my additional cable done, they pulled cable through on a Friday morning and left it coiled up next to the pavement which was a trip hazard.

So over the weekend I dug 12" deep into the ground, and buried the green cable ducting in sand and covered with protection to the same standards and regulations as any other cable.

Connected it up in brown box, then Monday morning first thing guy came to fix my telephone as they damaged it.. When he did that he connected up the other end inside the pit.

Late afternoon 2 guys turned up to bury the cable, but I told them it had been done already and they said they wouldn't of buried it more than few inches.. So I sent them away.. Was a bit annoyed they was, but at least now it's been done properly.

That other cable you mentioned is a telephone cable, the telephone was probably still connected on the old cable, and because everything was left connected the other end on the old cable they just left the telephone cable on the new one unterminated.

Handy to leave that in case you get a telephone cable problem they can switch that to new cable as well.

They don't use single cable, as they only have single cable for above ground usage, the underground dual cable is used because it has a tougher plastic insulation and the telephone wires are also covered in a waterproofing jelly. So if the duct gets flooded it remains waterproof and resistant to damp better whereas normal cable might fail sooner in those conditions.

[Coffeeguy]

The repull was done because of dropouts but it was the same with the new cable which is roughly the same thickness as the previous cable. The formatting here isn't so nice so I've snipped out the useless info

Cable Modem Downstream
Power Level (dBmV) -0.70 -0.02 -0.14 -0.23
RxMER (dB) 34.93 33.72 34.93 35.25
Correctable
Codewords 191989 1116337 136540 65095
Uncorrectable
Codewords 291 300 290 286

Cable Modem Upstream
Modulation 16QAM N/A N/A N/A
Symbol Rate(KSym/sec) 5120 N/A N/A N/A
Power Level
(dBmV) 42.50 N/A N/A N/A
T1 Timeouts 0 0 0 0
T2 Timeouts 0 0 0 0
T3 Timeouts 4 0 0 0
T4 Timeouts 2 0 0 0

[RB2004]

All looks fine on that cable,

Upstream is within tolerance,
Downstream is perfect as its close to 0, SNR slightly on low side but above 32 which would suggest a higher level of noise on the network...which is why loose connections and unterminated connections dont help.

Sephiroth states,

SNR (RxMER) - DOWNSTREAM

64QAM 29 dB minimum; 32 dB or above desired
256QAM 32 dB minimum; 35 dB or above is desired

See here for full details,

http://community.virginmedia.com/t5/...ER/td-p/148068


Was SNR any higher on the new cable? if not then i'd just leave it on the current cable and terminate the spare one if all works fine, will reduce noise introduction, and reduce vm network signal leak.. As well as protect the inside of the cable from dampness should it be needed in future.

Those T3s are probably a vm network problem.

I was T3 free until they gave Me 6 channels, now I'm getting up to 12 a day, but because my services aren't broke they won't fix it or acknowledge it as a problem.

So it's a case of. "when networks find or notice it as being a problem" it will be fixed but until them nothing will be done.

I was also told T3s can be caused by upstream congestion at the CMTS which is on VM headend.

Heres mine,

Upstream



nice 42 T3 errors since last reboot, lol but I tried to get VM to fix it but they wont...so its a problem on their network, like yours probably.

Downstream

[jb66]

Snr always appear lower on a vmng300

[RB2004]

Then all is fine

Wish vm would fix my T3s though.. 42!
But when I phoned them they didn't wanna know

[kwikbreaks]

Originally Posted by ferretuk

Suggest some research on transmission lines, impedance matching and reflections...

You'd get more standing waves on an unterminated or shorted coax than one terminated with a slightly incorrect resistive load. That said I'd personally just leave it if my connection was working OK.