Exposed VM coax cable in junction box
 

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?

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 :)

Re: Exposed VM coax cable in junction box
 

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

Re: Exposed VM coax cable in junction box
 

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?

Re: Exposed VM coax cable in junction box
 

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...

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.

Re: Exposed VM coax cable in junction box
 

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.

Re: Exposed VM coax cable in junction box
 

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.

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.

Re: Exposed VM coax cable in junction box
 

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

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

https://www.cableforum.co.uk/images/...2012/08/98.jpg

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

https://www.cableforum.co.uk/images/...2012/08/99.jpg

Re: Exposed VM coax cable in junction box
 

Snr always appear lower on a vmng300

Then all is fine :)

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

Re: Exposed VM coax cable in junction box
 

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.

Re: Exposed VM coax cable in junction box
 

this is why there are splitters in cab

Re: Exposed VM coax cable in junction box
 

While we're on the subject, does anyone know why one of my downstream channels is a whole dB and a bit below the other 3 channels? I've checked with my neighbour and his Superhub reports the same phenomenon:

Cable Modem Downstream
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Power Level
(dBmV) -0.34 0.29 0.18 0.03
RxMER
(dB) 34.93 33.72 34.77 35.25
Correctable
Codewords 7670 68030 6237 2205
Uncorrectable
Codewords 1009 295 316 303

It's because different frequencies have different losses. Higher frequencies more than lower frequencies.

Also
I gather there is some kinda setup on the amp in the cabinet which dictates this also.

Re: Exposed VM coax cable in junction box
 

They were all level at 35 a couple of days ago for maybe an hour or two but the one channel has always been 1.5~ dB below the rest. Not that is causes any problems but interesting to know nonetheless

Re: Exposed VM coax cable in junction box
 

The amps pump out higher frequencies at a higher level than low as high frequencies loose more signal over a shorter distance compared to low signals. So if your close to the amp usually high frequencies are higher and if your far away high frequencies are lower than low frequencies. It's basically a balancing game

Re: Exposed VM coax cable in junction box
 

Thanks jb, that explains it as I live literally next door to the cab and I suppose this is why my SNR never goes above the figure reported. Is there anything I can do to improve or boost this. I see some reports of people who have a SNR of 43.

Re: Exposed VM coax cable in junction box
 

No, that's VM's job.

Re: Exposed VM coax cable in junction box
 

Yes you can get that...

Downstream Channels
Lock Status Channel ID Frequency Modulation Rx Power SNR Pre RS Errors Post RS Errors
Locked 80 467000000 Hz QAM256 4.9 dBmV 42.6 dB 10202 0
Locked 76 435000000 Hz QAM256 6.4 dBmV 43.3 dB 1950 0
Locked 77 443000000 Hz QAM256 6.2 dBmV 43.4 dB 2427 0
Locked 78 451000000 Hz QAM256 6.3 dBmV 43.2 dB 2769 0
Locked 79 459000000 Hz QAM256 5.6 dBmV 43.2 dB 3520 0

You can but it depends on your local network.

The reason some is higher than other with same signal strength is because of noise on the line.

This can be caused by unterminated connections, loose connections, customers doing DIY modifications using improper stuff and / or methods, some equipment as jb66 said reporting lower snr than other equipment, damaged cables, tired lasers in the nodes etc.. Lots of factors.

Terminating unterminated connections, making sure that connections are tight but not over tightened... And if really must do modifications.. Using proper quality cable, connectors, splitters and methods etc might not drastically increase snr or even give a noticeable difference but it all does a little bit to help.

Yes it's VMs problem, and they are slowly refurbishing cabinets and I heard a while back sent all engineers on a particular day going round tightening connections. So they are trying to fix it.

But as fast as they are, some installers are still making installations with loose connections (loosely hand tight) and contractors doing cable repulls are leaving unterminated cables which in turn undermine vm efforts.

But while not our responsibility as customers, we do often pay a lot and want a performing network as much as vm do... So it doesn't cost anything for us to nip up loose connections in our own homes.. Just a little more than hand tight is fine.. Not so much it breaks your equipment as that would be stupid.

As tesco would say every little helps

Re: Exposed VM coax cable in junction box
 

Heh. Will VM be upgrading cabs during the speed upgrades?

Nope that is separate, as far as I'm aware the cabinet refurbishment is an ongoing project that has been ongoing a while and still is.. They are going around tidying up the cabinets, repairing them, replacing tired amps and node lasers, some also seem to be getting repainted grey.

Re: Exposed VM coax cable in junction box
 

Those MER figures are a bit too low IMO. Note that the channel with 33.72 has counted over 68K of errors compared with your best of just 2K.
This suggests that it is very marginal for 256QAM.
Also having any uncorrectable errors (if the SH stats are true) can lead to T3 if the codewords relate to a CMTS range response.

Re: Exposed VM coax cable in junction box
 

I hope you don't mind my coming in late.

The VMNG300 shows rising correctable codewords (but no uncorrectables). This is consistent with the lowish SNR reported by the modem. Eeps noticed this too. The uncorrectables you had at the time are highly likely to be what happens at boot time when the modem starts out in a non-graceful state. So I wouldn't read anything into those values. If the uncorrectables grow, then VM would have a case to answer.

As regards the one channel having a power level difference; unfortunately you stripped out the frequency data from your stats. if the first channel frequency is higher than all the others, it would explain the difference as JB66 has also explained. If the frequency is lower, then the cabinet amplifier is out of slope and needs adjusting.

HTH.
Throughout this thread you have been correctly advised by RB2004.

Re: Exposed VM coax cable in junction box
 

Good to hear that's an ongoing project. Quite a few cabinets are badly damaged where I live in North Camp, Farnborough so a refurb is badly needed here.

I've been asking VM to fix them and they like to drag their feet in eventually fixing them only for the installers to bust the lock open (with screwdriver and a mallet) and no I'm not joking as I've seen it happen in front of me twice so frankly given up getting getting it fixed again if that's the attitude of their installers :rolleyes:

Re: Exposed VM coax cable in junction box
 

Haha engineers bruteforcing cabs! Should've video'd and put it on Youtube.

Seph, sorry thought it was meaningless but yes, the frequency increases chronologically

Frequency 299000000 307000000 315000000 323000000
Power Level
(dBmV) -1.05 -0.40 -0.53 -0.59
RxMER
(dB) 34.48 33.38 34.48 34.93
Correctable
Codewords 786305 4416722 518646 219480
Uncorrectable
Codewords 314 314 329 312

Touch wood there have been no T3 timeouts since fitting the terminator last Sunday. I even capped my neighbours coax who unsubbed and moved over to Infinity a while ago. Surprised his coax was live and worked with my modem! Thanks for everyone's input, very much appreciated

Re: Exposed VM coax cable in junction box
 

That means the amplifier is out of slope - but not so as to worry. The SNR is poor though although not far from being in the optimum range.

The SH in modem mode would eliminate the VMNG300 being on the way out.

Re: Exposed VM coax cable in junction box
 

I'm not sure it's the amp characteristics. Here are my five down stream...

Locked 140 290750000 Hz QAM256 3.8 dBmV 43.2 dB 4730 25
Locked 141 298750000 Hz QAM256 3.9 dBmV 43.2 dB 4548 12
Locked 142 306750000 Hz QAM256 3.8 dBmV 43.2 dB 4513 11
Locked 143 314750000 Hz QAM256 3.7 dBmV 43.2 dB 4625 17
Locked 144 322750000 Hz QAM256 4.2 dBmV 43.9 dB 1304 0

The first four were the originals and the fifth was added about 4 months ago. This has about 0.5dB higher amplitude and 0.7dB better SNR.
My guess is that this fifth channel is provisioned from a different line card in the CMTS.

Re: Exposed VM coax cable in junction box
 

I didn't say the amp characteristics were a cause of the OP's problem.

But looking at your stats, Eeeps, or rather your closing statement - the fifth channel MUST be on the same line card as the others. You are terminated on one line card, not on two. Generlly speaking (but not mandatory in DOCSIS 3), downstream channels 2 onwards are separated by 8 MHz bandwidth, which is your case. The fifth channel arises becasue VM are load balancing across as many downstream channels as are available to a network segment and which have high SNR.

Re: Exposed VM coax cable in junction box
 

How can you tell if its out of slope? there all mid range frequencies shown

Re: Exposed VM coax cable in junction box
 

Frequency 299000000 307000000 315000000 323000000
Power Level(dBmV) -1.05 -0.40 -0.53 -0.59
RxMER(dB) 34.48 33.38 34.48 34.93

Because attenuation increases with frequency, the huighest power level should be at 299 MHz, not tbhe lowest

But it's not out in a link destroying manner. Just an observation.

Re: Exposed VM coax cable in junction box
 

I thaught you were looking at that.

The amp may still be sloped correctly but the lenth of the cable and the thickness of it determines the outcome at the house.

For example the 411 frequency may be 15db on a tap and 691 shoukd be higher say 20db. After 60m or so at the end of he drop you find that 411 is 4db but 691 is 0db.

So if the op above is close to the amp then the highest frequencies should be higher than the low as that's the way the amp is set up and the cable isn't long enough to even them out.

Anyway it's 0.5db and it will be playing no part in the issue :)

Re: Exposed VM coax cable in junction box
 

Actually it doesn't have to be part of the CMTS at all or even in the same building, VM have used E-QAM architectures in some places IIRC.