55 DbmV upstream power level - Page 2

Steve Day · 13-01-2009, 22:44

ok this is tonights installment...

when the cable installer did his job 3+ years ago he ran at my request a fairly long black cable from the box outside my house, thru the garage and up the back wall to the room i wanted the internal cable point in.

tonight...
i pulled on the black cable which was turned hard thru 90 degees to exit thru a doorframe, giving it some slack and presto.. my upstream suddenly became 45-47.

i will of course have to discuss this with the engineer tomorrow as to whether the cable is busted inside the sheathing.

whats inside the black cables that go from the street to your house? is it fibre optic? and can they indeed fracture or become a source of interference if bent hard enuf?

Steve

moaningmags · 13-01-2009, 22:56

It's coaxial cable from the street to the house.
If it's damaged, they may need to book a repull, re-laying the cable to your house.

Steve Day · 13-01-2009, 23:17

ok i am ammending the description in my last post. the cable from the street ends in a small box on my house front wall. from this small box exits the potentially faulty black cable which goes across my front wall, thru the garage and up the back wall to the internal cable modem socket/white box.

i have just been outside tracing all this stuff like i should have earlier

i hope this makes more sense now

is this black cable still coax? only it seems very tough and "plastic" to be coax, i doesnt seem to want to bend easily.

Steve

Stabhappy · 13-01-2009, 23:37

It doesn't bend easy because it's full of soft metal, as aposed to plastic and glassy materials like that in fibre.

LaineY · 14-01-2009, 01:44

Yeah.. its the Coax Cable..

I have a similar set up to you...

It comes from the Main Headend to the Regional Headend for your area.. then normally from there to the box in your street (Normally Green).. Converts from Optical/Fibre (Light) to Coax (RF) where it runs along the ground through trunking to the Sub Box (Depends, Closer to the property) then to the Omni box (Box with a cover over it) which is normally outside your wall...then.. there will be the same cable (Black Coax) which is running along up through your garage and to upstairs.

If this is in anyway Damaged a repull will be required to get that Coax replaced..

Any Upstream/Downstream signal issues i have had .. have normally been resolved @ the box in the street or the Sub Box (Manhole) in the ground out front..

In 14 years i have only had to have the power levels repaired twice..
Everytime my problem was resolved....

Hope this helps...

Ignitionnet · 14-01-2009, 13:01

Quick FYI from the newsgroups:

Quote:

Hi Broadbandings,

I must apologise, I have been misinformed regarding the use of attenuators.
As you suspected you cannot add an attenuator to lower the upstream power
level. Sorry for the mix-up.

-- Kind Regards Lee Grant Virgin Media Technical Support

---------- Post added at 12:58 ---------- Previous post was at 12:54 ----------

Quote:

Originally Posted by caph

Sounds like it could be BS to me too but the only logical conclusion to that is that service engineers deliberately lie to customers to fob them off. It's possible but it leaves a bad taste in my mouth. His words were more along the lines of - they're up to their neck in it and the power levels are all over the place and will be until they're finished.

Sorry to jump thread but you are almost exactly describing my current UCD problem apart from the downstream problem.

My event log is showing continual critical errors of "Started Unicast Maintenance Ranging - No Response received" followed by the UDC message. And my upstream power levels keeps getting higher and higher (hit 60db tonight). The only thing is my downstream power is 0.6 and my downstream SNR is a healthy 36.3. Can you think of any reason why my modem keeps shouting but not getting a reply?

Hrm they might be doing work cleaning up the network in preparation for the 50Mbit but it shouldn't be breaking things and extra extra combining should be done at the hubsite's RPM and not affecting current services as the combining will be to the new equipment not the current stuff.

With my tech hat on and being sober for a change, you are losing your upstream channel - there's too much attenuation on your upstream path and the CMTS / uBR isn't able to hear you properly and is requesting transmit power increase, or doesn't hear you at all - which is why you aren't getting a ranging response - the CMTS can't respond when it didn't hear anything.

The UCD message likely indicates you have changed upstream, you lose your lock on the upstream you were on and move to a new one, the new one has a different UCD hence the message.

You really do need a tech to sort your return / upstream path.

---------- Post added at 13:01 ---------- Previous post was at 12:58 ----------

Quote:

Originally Posted by Steve Day

is this black cable still coax? only it seems very tough and "plastic" to be coax, i doesnt seem to want to bend easily.

Steve

Decent coax not the 99p for a kilometre stuff is quite tough and 'plastic' - it's supposed to have multiple levels of shielding for the inner core of the cable

Joxer · 14-01-2009, 13:12

The common kind of coaxial cable used for TV aeriels etc has a copper core, the kind used for cable TV/Broadband has a stainless steel core with a copper coating, as you probably are aware stainless steel is a lot harder to bend than copper, though it is more brittle so a 90 degree bend could have caused a fracture which while not a complete break could degrade performance and could also be frequency specific.

Ignitionnet · 14-01-2009, 13:17

That it is much cheaper than a pure copper core is merely a bonus

General Maximus · 14-01-2009, 13:23

I agree, the tensile strenght of steel is conisderably greater than that of copper. http://en.wikipedia.org/wiki/Tensile_strength

Feenix · 14-01-2009, 13:24

and to reduce costs, and the fact that the copper is only required on the outside of the core due to skin effects. 90 degree bends are know to have serious attenuation issues on coax, hence the minimum bend radius specifications.

Joxer · 14-01-2009, 13:31

Maybe I am wrong about the stainless bit, but I would have thought it would be to add tensile strength rather than flexibility.

---------- Post added at 13:31 ---------- Previous post was at 13:29 ----------

Actually, thinking about it, the crushing of the dielectric will cause issues as well.

Ignitionnet · 14-01-2009, 13:34

Quote:

Originally Posted by Joxer

Maybe I am wrong about the stainless bit, but I would have thought it would be to add tensile strength rather than flexibility.

---------- Post added at 13:31 ---------- Previous post was at 13:29 ----------

Actually, thinking about it, the crushing of the dielectric will cause issues as well.

Well I'm sure it'll be fine once the offending cable has been dealt with.