How can I tell what my attenuation "should" be?

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Behodar

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#120783 13-Jun-2013 15:29

Hi,

My ADSL2+ modem currently reports downstream attenuation of 27 dB. According to this calculator, that's a line length of about 2 km. That doesn't seem right.

I have a master splitter and I'm about 450 metres past the "VDSL zone" on the Chorus maps, which according to the documentation represents a 700 m line length. I therefore estimate that my attenuation should be about 16 dB.

I'm aware that sometimes the line doesn't take the most direct route, but even then a 2 km length doesn't make sense. I'm about 200 m from the the end of the street so if I treat the line as going down the other side of the street, getting to the end, looping around, then coming back up to my place then that's still only about 1.6 km or maybe 22 dB.

There's a small side street. If the cable goes down and back up it, then that's a total of about 1.4 km to my house. Even if I combine both the side street and the "loopback" (which I find unlikely due to the layout) then it still only totals 1.8 km; I admit that 200 metres or 2 dB isn't likely to make much difference but I still can't make sense of these figures. There are no other streets attached to this cabinet.

Is there a way to determine what your attenuation or line length should be? Should I be logging a fault with my ISP since the attenuation is about 10 dB higher than I'd logically expect?

Thanks :)

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#836381 13-Jun-2013 15:29

Hello... Our robot found some keywords in your post, so here is an automated reply with some important things to note regarding broadband speeds.

If you are posting regarding DSL speeds please check that

- you have reset your modem and router

- your PC (or other PCs in your LAN) is not downloading large files when you are testing

- you are not being throttled by your ISP due to going over the monthly cap

- your tests are always done on an ethernet connection to the router - do not use wireless for testing

- you read this topic and follow the instructions there.

Make sure you provide information for other users to help you. If you have not already done it, please EDIT your post and add this now:

- Your ISP and plan

- Type of connection (ADSL, ADSL2, VDSL)

- Your modem DSL stats (do not worry about posting Speedtest, we need sync rate, attenuation and noise margin)

- Your general location (or street)

- If you are rural or urban

- If you know your connection is to an exchange, cabinet or conklin

- If your connection is to a ULL or wholesale service

- If you have done an isolation test as per the link above

Most of the problems with speed are likely to be related to internal wiring issues. Read this discussion to find out more about this. Your ISP is not intentionally slowing you down today (unless you are on a managed plan). Also if this is the school holidays it's likely you will notice slower than usual speed due to more users online.

A master splitter is required for VDSL2 and in most cases will improve speeds on DSL connections. Regular disconnections can be a monitored alarm or a set top box trying to connect. If there's an alarm connected to your line even if you don't have an alarm contract it may still try to connect so it's worth checking.

I recommend you read these two blog posts:

- Is your premises phone wiring impacting your broadband performance? (very technical)

- Are you receiving a substandard ULL ADSL2+ connection from your ISP?

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plambrechtsen

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#836394 13-Jun-2013 15:39

Do you have a master filter. If you are a Telecom customer I can run a line test and see what is going on.

Behodar

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#836411 13-Jun-2013 15:53

Yes, I have a master filter but I am not a Telecom customer (Maxnet).

mercutio

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#836481 13-Jun-2013 17:34

Behodar: Hi,

My ADSL2+ modem currently reports downstream attenuation of 27 dB. According to this calculator, that's a line length of about 2 km. That doesn't seem right.

Is there a way to determine what your attenuation or line length should be? Should I be logging a fault with my ISP since the attenuation is about 10 dB higher than I'd logically expect?

Thanks :)

good luck :)

i got as far as finding out my neighbours have the same problem for my connection.

i don't think there are any plans to improve existing adsl connections that work.

and really, to me, it's no consolidation that my neighbours have the same problem.

i'm ~16db down ~5.5 up at 600 metres with 15 megabit sync, on the same side of the same street as the cabinet. although i'm pretty sure it's double backing in my situation, as the grey box thingy is on the other side of the street from me. i imagine it must be from quite far up the road.

i remember hearing about how in some older areas it's common to have the same pair go a few km up the the road and have multiple offshoots on it back from the party line days, so although the cable may have a short distance to go it may have an extension still connected further away.

also i've experienced growing attenuation over time in multiple locations. i expect if there's only a cabinet every 2 km or so then there could be longer line lengths increasing the amount of crosstalk.

is your sync under 10 megabit? if so, and it says that your place should be capable over 10 megabit you may as well complain, but don't get nasty with the maxnet employee, the more people with tickets to chorus, and you never know, maybe they'll shorten the loop lengths.

in my instance my property says > 20 megabit with the right modem/plan. but i'm more after getting vdsl, and was hoping to get attenuation fixed first. but apparently my prequal passes anyway.

i've seen a few instances of this kind of thing recently. and it'd be interesting if you can find out what someone on the other side of the street syncs at. although isp's can only check customers on the same isp, so it's slightly complicated unless chorus give an answer.

and if you try logging a fault, they'll probably just say "no fault found" as it's not a problem on your line, but in general.. well that's what i'm expecting.

Batman

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#836488 13-Jun-2013 18:01

Whats your line speed? If it's ok then ... Oh well :)

chevrolux

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#836492 13-Jun-2013 18:21

'Visual distance' to a cabinet or exchange can vary greatly depending on how the service have been run in your street/suburb.
The only way to know for sure would be to look at the plans for your RLG and determine actual cable length from that.

I had a customer that was about 500m down the foot path from a cabinet but only got 15Mbps speeds. Looked up the plans and because the of the FTTN project the cabinet had been moved across the road so his cable actual went all the way down one side and then crossed and came back. Actual length was closer to 2km.

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Behodar

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#836497 13-Jun-2013 18:36

OK, let's see here...

1. My line speed is currently 15483/1208 so it's not bad in any sense of the word but I could really do with faster upload. I've tried to order VDSL in the past but had it rejected, but if I have a line fault and can get the attenuation down then I'll certainly try it again (even though I'm a little way out of the dark brown zone on the map, I've heard that Chorus is a bit more lenient now, indeed I read here on GZ a couple of weeks ago about someone on VDSL at 1.3 km that gets better speeds than I do now).

2. I have no intention of getting nasty with the Maxnet employee because I know that it's not their fault :)

3. No* houses on the other side of the street (there's a park there). I probably should've thought about that when I came up with my "cable may loop around the end of the street" theory!

*There are actually three houses to this side of the park but are down long driveways and are not visible from the street, therefore I've never met the people there etc. and don't want to go barging in asking to look at their DSL stats :)

RunningMan

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#836506 13-Jun-2013 18:50

mercutio:

in my instance my property says > 20 megabit with the right modem/plan. but i'm more after getting vdsl, and was hoping to get attenuation fixed first. but apparently my prequal passes anyway.

>20Mb indicates the VDSL area - the right modem being a VDSL one.

mercutio

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#836507 13-Jun-2013 18:52

RunningMan:
mercutio:

in my instance my property says > 20 megabit with the right modem/plan. but i'm more after getting vdsl, and was hoping to get attenuation fixed first. but apparently my prequal passes anyway.

>20Mb indicates the VDSL area - the right modem being a VDSL one.

ohh... that wasn't made clear at all.

maybe will just have to jump to vdsl.

mercutio

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#836511 13-Jun-2013 18:54

Behodar: OK, let's see here...

1. My line speed is currently 15483/1208 so it's not bad in any sense of the word but I could really do with faster upload. I've tried to order VDSL in the past but had it rejected, but if I have a line fault and can get the attenuation down then I'll certainly try it again (even though I'm a little way out of the dark brown zone on the map, I've heard that Chorus is a bit more lenient now, indeed I read here on GZ a couple of weeks ago about someone on VDSL at 1.3 km that gets better speeds than I do now).

2. I have no intention of getting nasty with the Maxnet employee because I know that it's not their fault :)

3. No* houses on the other side of the street (there's a park there). I probably should've thought about that when I came up with my "cable may loop around the end of the street" theory!

*There are actually three houses to this side of the park but are down long driveways and are not visible from the street, therefore I've never met the people there etc. and don't want to go barging in asking to look at their DSL stats :)

well chorus can actually look it up, try getting maxnet to put through a query about line loop length and expected attenuation maybe? hopefully someone from there can look up what other places get :)

fwiw i only get 1144 kbit upload, so you're doing better than me at least. how far are you away from an exchange? you may be able to do annex m with LLU. i really wish the cabinets did annex m.

RunningMan

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#836514 13-Jun-2013 18:57

mercutio:
ohh... that wasn't made clear at all.

maybe will just have to jump to vdsl.

The new Chorus SAT isn't all that intuitive....

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mercutio

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#836515 13-Jun-2013 19:00

RunningMan:
mercutio:
ohh... that wasn't made clear at all.

maybe will just have to jump to vdsl.

The new Chorus SAT isn't all that intuitive....

true. i normally use http://bcc.telecomwholesale.co.nz/#

Behodar

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#836523 13-Jun-2013 19:20

I vaguely recalled getting some stats once and sure enough I just found this from when I tried to order VDSL 18 months ago (before Chorus seemingly relaxed the rules):

Serving LWC Name    WHK - WHK/A
HDB3 Present in Binder    No
Line Attenuation    13 - 18 dB
Download Rate Range    ADSL2+: 11.6 - 13.0 Mb/s, VDSL2: 14.7 - 0.0 Mb/s
Upload Rate Range    ADSL2+: 1.0 - 1.1 Mb/s, VDSL2: 1.5 - 0.0 Mb/s
Upload > 300kb/s    No
Urbanisation Level    Rural
Result Positive For    BUBA FS/FS, EUBA 40, EUBA 90, EUBA 0, EUBA 180, BUBA 256/128
Result Negative For    WVS 0, NGA Evolve 1, NGA Evolve 2, NGA Evolve 3, NGA Evolve 4, NGA Evolve 5, NGA Business 1, NGA Business 2, NGA Education 1, NGA Education 2, NGA Education 3
Result Inconclusive For
DSL Available at LWC    Yes
Access Types    Copper
Messages    ADSL2+, VDSL2; Connected UBA ASIDs 1624161012

Does this indicate that I should be getting 13-18 dB at my place?

cyril7

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#837608 16-Jun-2013 14:08

Hi Behodar, cannot comment on the specifics of your line, but I was at a house yesterday that was on the Telecom VDSL2 trial, had 13.5dB attenuation and sync'd at 42Mb/s down, 10Mb/s up and by my reckoning (my trip meter as I drove away) was 800m from the Exchange.

I should point out that this house had previously had a master filter installed by Chorus specifically for the VDSL2 service, the filter had been installed directly behind the faceplate at the modem post several phone sockets (with non filtered phones including a pert on them) and had 8m or so or trurip from the demarc to a screw terminal mess in the ceiling. Would be interesting if Chorus credit the master install cost. Before I arrived the sync was 20Mb/s up and 10Mb/s down and showing 14dB atten.

Cyril

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#837749 16-Jun-2013 18:56

cyril7: Hi Behodar, cannot comment on the specifics of your line, but I was at a house yesterday that was on the Telecom VDSL2 trial, had 13.5dB attenuation and sync'd at 42Mb/s down, 10Mb/s up and by my reckoning (my trip meter as I drove away) was 800m from the Exchange.

I should point out that this house had previously had a master filter installed by Chorus specifically for the VDSL2 service, the filter had been installed directly behind the faceplate at the modem post several phone sockets (with non filtered phones including a pert on them) and had 8m or so or trurip from the demarc to a screw terminal mess in the ceiling. Would be interesting if Chorus credit the master install cost. Before I arrived the sync was 20Mb/s up and 10Mb/s down and showing 14dB atten.

Cyril

Hi Cyril, just for your info, the VDSL splitter is supposed to be installed behind the jackpoint that services the VDSL Modem in houses that can only be done by using pre-existing wiring. The POTS (Plain Old Telephone Service) circuit is then to be "back-fed" from that point. Theoretically the installation should be done with a new Cat5e cable from POE (Point of Entry) to Modem JP, the reality is this sometimes cannot be done and existing wiring is used, although the pairs should be "groomed" to give as perfect circuit as possible. Great that you fixed their line and increased their speed dramatically.

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