Copper Distance from PCP

Hey guys - i am trying to determine the distance from the cab to my house, i live in an estate where the houses circle themselves, if i take shorter route its 100 meters and the longer route its 300 meters,

Anyway to determine which way the copper is running ?

Not really, unless you ask an engineer

Why does it matter?

Possibly to estimate G.fast speeds

Any other clues such as is overhead from a pole; or is it underground and manhole covers may help.

Absolutely - correct, would be nice to know if G.FAST is on the horizon,
if it helps, the cable is underground

My router reads attenuation of 8.1

Easier to look at www.dslchecker.bt.com

The attenuation is a good guide as well. Looks like you have a short line. Is that VDSL attenuation?

Modem Says - vdsl2

Definitely the shorter route then.

Great to know this really - hopefully g.fast will be near the advertised speeds

In reply to a post by asrab:

Absolutely - correct, would be nice to know if G.FAST is on the horizon,
if it helps, the cable is underground

My router reads attenuation of 8.1

Make no diffrence in attenuation of 8.1. Because I remember I was on ADSL2+ with a line attenuation of 28.9dB but after change over to VDSL2 the line attenuation was 10.9dB but it now changed again with line attenuation of 11.7dB.

Engineer say I was estimated 250m away from the fibre cabinet with line attenuation of 10.9dB back in 2014.

For your line attenuation of 8.1dB are probably around 100m to 150m away in my guess.

You can ask the ISP to run the GEA Test as it will tell you the line estimated. My GEA test say mine is below:

Estimated Line Length In Metres 243.6

So, the engineer are spot on within 250m away when he installed my fibre in 2014.

Edited by adslmax (Tue 26-Sep-17 00:27:22)

For comparison, my Line Down Attenuation is 13.4 db, at about 300 Metres Copper distance from the FTTC - although that FTTC Cabinet is only about 10 (ten) Metres from my front door; and I can see inside it from my lounge when it is opened.

Very strange routeing on a pre-wired greenfield site in 1967!

Great - I will get in touch with Talk Talk and see if they are able to preform an GEA test,

In reply to a post by eckiedoo:

For comparison, my Line Down Attenuation is 13.4 db, at about 300 Metres Copper distance from the FTTC - although that FTTC Cabinet is only about 10 (ten) Metres from my front door; and I can see inside it from my lounge when it is opened.

Very strange routeing on a pre-wired greenfield site in 1967!

Just shows how much the wiring can vary, i live in an area which i would guess has old wiring, perhaps that means that it is thicker? But my router shows a fairly consistent 13.1db downstream attenuation at ~550m.

Very interesting of shoot topic - I wonder how wire thickness/quality affect distance and attenuation

My copper wiring is under the ground all the way to the telephone exchange by 1.2 miles away and it was 1974 copper wiring say the engineer.

A thicker, longer guage cable can perform the same or better than a shorter, thinner guage. As to what the ratio is I don�t know.

I�m about 6000m from the cab with a 19.3dB attenuation, 77.8meg sync with G.INP and 3dB target margin. Full Huawei 128 cab.

In reply to a post by lee111s:

A thicker, longer guage cable can perform the same or better than a shorter, thinner guage. As to what the ratio is I don�t know.

I�m about 6000m from the cab with a 19.3dB attenuation, 77.8meg sync with G.INP and 3dB target margin. Full Huawei 128 cab.

6000 meters? Hopefully that's just a case of hitting "0" too many times haha

Haha yeah, 600m

Electric current travels mainly along the circumference/outside of a wire, rather than down the middle. So basically a thicker wire has a wider path for it, hence lower resistance/attenuation. Which in turn means greater distance. Ceteris paribus.

I'm about 380m away from my Huawei 384 cab. Think the attenuation started off at around 12db in 2014. 13.8db now. 55/20 without G.INP @ 6db.

Agreed Robertos.

And if I remember my theory correctly from many decades back, the higher the frequency, the more concentrated towards the surface.

If the wire radius is doubled, then that surface area is quadrupled, reducing the effective resistance/impedance to about one-quarter (25%).

Taking a more likely maximum radius increase for phone wiring of 1.414... , then the surface area is doubled etc.

Help!

Is that a 3 db or 6db improvement?

I suspect 3 db, so my 13.4 db would reduce/improve to about 10.4 db Attenuation.

Hey Guys - thanks for all your comments, i have been advised by my ISP the copper distance is 300 meters, according to their records

Wonder if attenuation of 8.1 is in line with that distance ?

In reply to a post by asrab:

Hey Guys - thanks for all your comments, i have been advised by my ISP the copper distance is 300 meters, according to their records

Wonder if attenuation of 8.1 is in line with that distance ?

Mine is line attenuation of 11.7dB on downstream the GEA Test come back result was Estimated Line Length In Metres 243.6.

Not sure why is your 300 metres away with very low line attenuation of 8.1dB. Ask your ISP to sent you a GEA Test result to your email or ticket.

Here is example of my GEA Test result from my isp below:

GEA test below
Test Outcome Pass
Test Outcome Code GTC_FTTC_SERVICE_0003
Description No problem found, OAM test is not currently supported on this line.
Main Fault Location OK
Sync Status In Sync
Downstream Speed 80.0 Mbps
Upstream Speed 20.0 Mbps
Appointment Required N
Fault Report Advised N
NTE Power Status PowerOn
Voice Line Test Result Pass
Bridge Tap Not Detected
Radio Frequency Ingress Not Detected
Repetitive Electrical Impulse Noise Not Detected
Cross Talk Not Detected
Estimated Line Length In Metres 243.6
Upstream Rate Assessment Very Good
Downstream Rate Assessment Very Good
Home Wiring Problem Not Detected
Downstream Policing Discard Rate 0.0
Customer Traffic Level Upstream and Downstream Traffic Detected
Technology VDSL
Profile Name 0.128M-80M Downstream, Retransmission Low - 0.128M-20M Upstream, Error Protection Off
Time Stamp 2017-05-22T16:00:00
Parameters MIN MAX AVG
Down Stream Line Rate 80.0 Mbps 80.0 Mbps 80.0 Mbps
Up Stream Line Rate 20.0 Mbps 20.0 Mbps 20.0 Mbps
Up Time 900.0 Sec 900.0 Sec 900.0 Sec
Retrains 0.0 0.0 0.0
Current and Last 15 Minute Bin Performance
Parameters Last Traffic Count(Upto 15 mins) Current Traffic Count(Upto 15 mins)
Start Time Stamp 2017-09-27T14:28:32Z 2017-09-27T14:43:32Z
Ingress Code Violation 0 0
Egress Code Violation 0 0
Errored Seconds 0 0
Severely Errored Seconds 0 0
Unavailable Seconds 0 0

Guess i will need to ask them for a full report - it is after all talk talk, be back shortly guys, for interests to anyone here is my modem readings :

***********************************************

DSL synchronization status:
Up
Connection status:
Showtime
Upstream line rate (kbit/s):
18998
Downstream line rate (kbit/s):
70479
Maximum upstream rate (kbit/s):
19758
Maximum downstream rate (kbit/s):
85424
Upstream noise safety coefficient (dB):
6.2
Downstream noise safety coefficient (dB):
6.6
Upstream interleave depth:
239
Downstream interleave depth:
1
Line standard:
VDSL2
Upstream line attenuation (dB):
0.1
Downstream line attenuation (dB):
8.7
Upstream output power (dBm):
6.7
Downstream output power (dBm):
13.8
Channel type:
Fast
DSL up-time:
0 days 9 hours 40 minutes 40 seconds

**********************************************

Fore some reason the modem got rebooted,

Here is mine:

DSL
Line Status:
DSL Modulation Type:
Annex Type:
Upstream Downstream
Current Rate(kbps) 20000 80000
Max Rate(kbps) 30490 97085
SNR Margin(dB) 15.7 10.3
Line Attenuation(dB) 0 11.7
Errors(pkts) 0 0

Wonder why your sync is a lot higher than mine - when the attenuation is somewhat lower, may be its the service provider or crosstalk as i know all my neighbours are on fibre services

Nothing to do with the ISP.

In reply to a post by lee111s:

Nothing to do with the ISP.

Are you sure ? My neighbour on the left has Sky, thier Sync speed is higher than mine however my neighbour straight in front of me has Plusnet and is worse than mine,

Yes, nothing to do with the ISP.

There are many variables in these lines. Look at the stats of my short line ...

Data rate:
20.00 Mbps / 80.00 Mbps
Maximum data rate:
36041 / 105629
Noise margin:
23.3 dB / 12.3 dB
Line attenuation:
9.4 dB

My theoretical max is higher than the others shown, yet the attenuation is different again. An accurate measurement with a TDR from NTE to DSLAM showed 220 m.

All these stats are just interpretations of the various inputs, they are indicators rather than gospel truths.

As Zarjaz says, the figures are indicators.

There are many, many factors which can influence the various factors: Diameter/gauge of the wire, quality of the copper, aluminium or even steel wire for some parts, the component quality in the modem and how close they are to ideal, chip-set, cross talk from other users, cable twist rate (or none), external noise from many sources including radio transmissions or domestic and industrial equipment, and quite a few more.

In reply to a post by asrab:

may be its the service provider or crosstalk

Crosstalk can be negligible or huge. In theory, it can steal more than half of your speed.

FEC and interleaving settings make a difference, with the worst case maybe stealing 20% of your speed.

In reply to a post by asrab:

In reply to a post by lee111s:

Nothing to do with the ISP.

Are you sure ? My neighbour on the left has Sky, thier Sync speed is higher than mine however my neighbour straight in front of me has Plusnet and is worse than mine,

Yes, as you�ve been told it�s nothing to do with the ISP. The DSLAM for FTTC (in the cabinet) is owned and managed by Openreach. It works different to ASDL based broadband.