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Author Topic: Does line attenuation increase in hot weather?  (Read 3882 times)

ktz392837

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Does line attenuation increase in hot weather?
« on: June 27, 2018, 02:58:57 PM »

Over the past month or so my line attenuation has gradually increased nearly 1db.  It has been up and down (perhaps when things cool down and warm up again) but this morning it is 1db higher than what is was about a month ago. 

It seems to make sense that heat may cause wires to expand but I am on relatively short line is the higher temperature causing a 1db increase a fair observation or is something else in play causing this?

Sync speed has been impacted but luckily only a few Mb lost (so far).

Thanks
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PhilipD

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Re: Does line attenuation increase in hot weather?
« Reply #1 on: June 27, 2018, 04:52:33 PM »

Hi

Temperature does make a difference to resistance but it isn't very much really and I doubt attenuation is changing due to heat affecting the copper wire.  (see https://www.cirris.com/learning-center/general-testing/special-topics/177-temperature-coefficient-of-copper)

It should be noted that attenuation reported by the router/modem is not normally a fixed measurement, but an average attenuation based on all the frequencies you receive which varies due to noise, and higher frequencies are attenuated more than lower ones, so depending on the range of frequencies the modem decides to use, the reported attenuation will vary.

The true attenuation (as used by BT) is measured at a fixed frequency of 300KHz, and in my experience on two lines I've closely monitored this has never changed.

That's not to say heat doesn't play a part.  If this is VDSL then the cabinet may be baking in the sun, and hot electronics struggle and can create more noise, plus your own equipment will be running hotter as well and be a bit more noisy.

Also depending on what other customers come online, go offline, or even go away on holiday turning their modems off, means that the connection profile is always changing.

The overall trend though for ADSL and VDSL is as time goes by, sync speeds tend to worsen due to cross-talk and more people moving to the same technology, and it never gets any better.  If you are lucky and have a short line length then you have enough margin to ride the storm so sync speed isn't hit but you will still notice the downward trend in SNR, but for most of us, it only gets worse*

Regards

Phil

* Sometimes it gets better, for example a change in the technology such as G.INP or a fault being fixed, but generally the trend is a worsening picture by time.









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ktz392837

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Re: Does line attenuation increase in hot weather?
« Reply #2 on: June 27, 2018, 06:29:31 PM »

Thanks very interesting. 

My line is a bit weird it gets best sync speeds at breakfast time.  I will try a resync then to see if I can get the speed back I lost. 

The power values on my line have also been 30% lower than normal for the past couple of weeks when I checked this morning, they returned to normal mid morning but are now 25% lower again

Had power cuts / problems throughout today they say these should be fixed now but during the morning I had 100's of ES/hr before modem was turned off to protect it from racking up ES or continually syncing, power cut, syncing again and repeat.  Back to my normal 1-10/hr now.  Probably total in low 2000 for ES today (2 resyncs) will I have angered the DLM gods?  Hopefully not - got a few hundred ES to spare and can certainly have more than 2 resyncs :)

ECI cab so no chance of ginp or 3db but my fingers remain crossed in hope one day it may happen.
« Last Edit: June 27, 2018, 06:42:27 PM by ktz392837 »
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konrado5

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Re: Does line attenuation increase in hot weather?
« Reply #3 on: June 27, 2018, 06:48:28 PM »

Yes. It increase about 0.4 dB.
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Weaver

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Re: Does line attenuation increase in hot weather?
« Reply #4 on: June 27, 2018, 07:15:36 PM »

> but I am on relatively short line

Of course, expansion is relative, a fractional change. So a change which is a multiplication by x means the same n dB exactly in every case.

I do think you raise an interesting point, as my sync speeds have been a bit low recently. However it could be the length of the day though, especially at my northern latitude: sunset 22:24 - sunrise 04:30 here.
« Last Edit: June 27, 2018, 07:19:14 PM by Weaver »
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ejs

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Re: Does line attenuation increase in hot weather?
« Reply #5 on: June 27, 2018, 07:24:55 PM »

A seasonal variation in attenuation is detectable on my long ADSL line. The lowest my downstream attenuation has been this year was 57.5 dB on 28 Feb, highest so far is it's current 58.6 dB.
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PhilipD

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Re: Does line attenuation increase in hot weather?
« Reply #6 on: June 27, 2018, 09:33:24 PM »

Hi

A seasonal variation in attenuation is detectable on my long ADSL line. The lowest my downstream attenuation has been this year was 57.5 dB on 28 Feb, highest so far is it's current 58.6 dB.

Is that attenuation from the modems stats?  Usually the modem doesn't report the real static attenuation figure, they report something different entirely.

My real attenuation is unchanged, and in this hot weather my SNR margin has gone from 8.0db to 8.7db, indicating better performance, as I already sync at 80/20 it doesn't change my sync speed.

I suspect seasonal variation is more about noise than changing attenuation.

Regards

Phil
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Weaver

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Re: Does line attenuation increase in hot weather?
« Reply #7 on: June 27, 2018, 10:03:22 PM »

If someone had an actual fault, then temperate might affect that, expansion of bad joints for example, a semi-contact becoming even more rubbish say.
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ktz392837

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Re: Does line attenuation increase in hot weather?
« Reply #8 on: June 28, 2018, 05:27:38 AM »

> DLM gods

Unfortunately I have angered the DLM gods.  Despite being below the 2880 ES, 20 resync limit with approximately 2100 ES and 2 resyncs it has added interleaving to the line.
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Ixel

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Re: Does line attenuation increase in hot weather?
« Reply #9 on: June 28, 2018, 09:22:35 AM »

> DLM gods

Unfortunately I have angered the DLM gods.  Despite being below the 2880 ES, 20 resync limit with approximately 2100 ES and 2 resyncs it has added interleaving to the line.

Interesting, I have also recently suffered interleaving on my connection with both upstream and downstream after multiple re-syncs occurred (but well under the believed threshold of 20 re-syncs and 2880 ES per day). From fastpath/fastpath it went to INP 4/3 and delay 8/8.

I originally thought it was a problem with my Gigaset base station but it may not just be that after all. I've changed the filter so far, the line test result still comes up as fine however (Line Test OK. Dial tone OK). I wonder if it's related to the hot weather in some way, usually I get a loss of sync every time I receive a phone call or make one, and there's been some rather large fluctuations on the upstream attainable rate (and sometimes downstream) once or twice a day recently. For example, one moment the upstream attainable rate is at around 12 megabits, 15 minutes later it shows as around 10 megabits, then 15 minutes later for several hours following that it's around 13 megabits (my program takes samples of the DSL stats every 15 minutes).
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ktz392837

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Re: Does line attenuation increase in hot weather?
« Reply #10 on: June 28, 2018, 10:31:40 AM »

Mine is now inp 3/0, delay 8/0 I do get about a 1db swing in db in both down and up through a 24h period with a swing in max attainable strangely not corresponding to db though (but that is the norm for my line). 

Power seems to change every so often currently on less power than what I would call normal, it did return yesterday but with the other issues it didn't stick.

I do seem to get a few hundred CRC errors when phone rings but nothing major.  I hardly get any incoming calls and use VoIP for most outgoing calls so I am generally happy.
« Last Edit: June 28, 2018, 10:42:10 AM by ktz392837 »
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spring

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Re: Does line attenuation increase in hot weather?
« Reply #11 on: June 28, 2018, 01:18:26 PM »

if you want to disable resyncs, you can turn off your device, unplug the dsl cable, turn it on, write "adsl connection --down", plug in your dsl cable, write "adsl connection --up --noretrain"

if you want your modem to drop sync when it detects an SES instead, it would be "adsl connection --up --noretrain --sesdrop on" [I think that's what it does....]

i think i've written those commands/steps in a way that works, never tried it, happy to be corrected
« Last Edit: June 28, 2018, 01:22:22 PM by spring »
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ejs

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Re: Does line attenuation increase in hot weather?
« Reply #12 on: June 28, 2018, 07:28:32 PM »

Is that attenuation from the modems stats?  Usually the modem doesn't report the real static attenuation figure, they report something different entirely.
Yes it's from the modem stats. As far as I know, my Netgear DG834Gv3 (AR7 chipset) modem reports the attenuation over the frequencies of the line in use. If for some reason it connected at a vastly lower speed, with the highest frequency in use being much lower, then it might report a lower attenuation. That's not what's happening. The line speed hasn't changed that much.

My real attenuation is unchanged, and in this hot weather my SNR margin has gone from 8.0db to 8.7db, indicating better performance, as I already sync at 80/20 it doesn't change my sync speed.
So you haven't noticed any changes in attenuation perhaps because your line to the FTTC cabinet is very short. Also I think the attenuation is only measured at the time the modem connects, so how long is your uptime? My uptime is typically a few days.

I suspect seasonal variation is more about noise than changing attenuation.
I really think it isn't. I noticed when an extra 2dB of noise arrived one day, which has been present almost continuously ever since, it affected the SNRM and the speed at the next re-connect, it didn't change the attenuation.
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ejs

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Re: Does line attenuation increase in hot weather?
« Reply #13 on: June 28, 2018, 08:02:40 PM »

Here's a rough graph of 2017 to give the general idea. The temporarily high speed on 22 June looks like reconnecting before everything else after a power cut, lots less noise, no difference in attenuation.
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