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Author Topic: Does very heavy rain improve your DSL signal?  (Read 3948 times)

Weaver

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Does very heavy rain improve your DSL signal?
« on: August 26, 2015, 10:08:38 AM »

Two questions, I realise

(1) Does torrential rain help your SNR ? Is that at all possible? (Or even the converse.)
There was a thread about this some while back, at :

http://forum.kitz.co.uk/index.php/topic,12732.msg240615.html#msg240615

(2) What happens if you submerge a (sealed, uncorroded) DSL cable in water ? Does that have a detrimental effect on HF, or help screen off noise, or both / neither ?

I sometimes get the feeling that in winter time my ADSL does well when the torrential rain is unrelenting. However, I ought to consider (3) the short nights vs long nights over the year  - a really big deal this far north - and the effect that that might have on averaged SNR over 24 hours.
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AArdvark

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Re: Does very heavy rain improve your DSL signal?
« Reply #1 on: August 26, 2015, 11:18:53 AM »

Personally, rain is noticeable by the fact it has a slight impact on the sync I get. (It drops and snrm drops)

I have a BT Joint box (pit in the floor) at the end of my drive.
I got to see the inside the last time an OR Engineer called and it does get water inside.
The cables apparently were NOT insulated from the water up to current spec. [Last opened 16 years ago when Housing estate built ! ]
The OR Engineer filled the cable joint (plastic box around cable ends) with silicon sealant (looked like red translucent bath sealant :) )

You may be taking the popular expression for non-optimal Telecomms as in 'Damp string & tin cans' too literally  :D :D ;)

[I had a 512kb (then upgraded to 1mb !!)  'Damp string' connection for years  ;D ]
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Weaver

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Re: Does very heavy rain improve your DSL signal?
« Reply #2 on: August 26, 2015, 06:13:47 PM »

Background for question (2) :-

The bundle for the entire village went into the stream and ran along under water for a very short distance, quite near to my house. High up on the moor this happens again in a few other places, and in many places the cable bundle is not buried, it just lies on the surface by the roadside, in a rocky shallow ditch which will only fill with water when there is heavy rain.

So for two or three miles a certain fraction of the length is under water whenever it rains. Many years back, rain used to mean water getting into the outer insulation, and there were also vulnerable joints in a couple of places. BT had even run the cable over stony ground over which vehicles were driving often, thus grinding the bundle to a pulp constantly. Over ten years ago, someone with a brain replaced the whole lot (I suspect), started again, joint-free (or at least almost so), and buried the short section that was being used as a doormat.
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AArdvark

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Re: Does very heavy rain improve your DSL signal?
« Reply #3 on: August 26, 2015, 06:32:28 PM »

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Weaver

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Re: Does very heavy rain improve your DSL signal?
« Reply #4 on: August 26, 2015, 06:53:20 PM »

@Aardvark - many thanks for those references. The second one deals with frequencies waaay too high for our purposes.

Quite a bit has been written about rainfall radar and polarisation, useful to the weather man.

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Weaver

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Re: Does very heavy rain improve your DSL signal?
« Reply #5 on: August 26, 2015, 07:00:59 PM »

Thing is, a lot of people who have latent faults find out they have a problem when water gets in where it shouldn't or corrodes a joint, as we all know. So it's hardly surprising that a lot of reports of the effects of rain are associated with people saying that their world just turned bad. But unless someone is watching their SNRM all the time they aren't going to see a beneficial effect anyway as DLM doesn't react quickly enough, especially when you add on ISPs' own rate-shadowing/DLM-tracking systems which impose yet more delay, so it seems to me that you would have to have a lot of sustained heavy rain over a long long period for it to make an impression.

So the question really is, do SNRM-watchers who have no faults or leaks see anything interesting when there's a lot of water about for a long period?
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lloyd

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Re: Does very heavy rain improve your DSL signal?
« Reply #6 on: August 26, 2015, 07:41:04 PM »

I've noticed for a while now that my u/s snrm goes down whenever it rains.  d/s gets affected as well, but nowhere near as much.  Does not need to be heavy, fine drizzle is enough. Attached is todays graph.
« Last Edit: August 26, 2015, 07:43:22 PM by lloyd »
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Weaver

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Re: Does very heavy rain improve your DSL signal?
« Reply #7 on: August 26, 2015, 07:46:15 PM »

Speculation: Unless this is connected with bad insulation or corrosion plus wetness, maybe wetness surrounding a cable hampers propagation of higher frequencies? So your SNR gets worse because your signal gets more attenuated, never mind noise.

Make sense? Or way off?
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Weaver

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Re: Does very heavy rain improve your DSL signal?
« Reply #8 on: August 26, 2015, 07:57:04 PM »

Why the discrepancy between ds and us in lloyd's graphs? (Obviously it's a frequency-dependent effect, but ...)

And why is it that way round? Confused.
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lloyd

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Re: Does very heavy rain improve your DSL signal?
« Reply #9 on: August 26, 2015, 08:33:46 PM »

My feed is overhead, so I suspect a bad joint at the top of the pole.
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lloyd

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Re: Does very heavy rain improve your DSL signal?
« Reply #10 on: August 30, 2015, 06:51:14 PM »

"Did it rain last night?" asked the wife this morning. "I don't know" was my reply, "I'll just check the broadband stats.".  Bizarre but true. Lovely indication of a few hours of probably light rain.

Amusing as this is, I'm getting concerned that performance during the autumn/winter might be severely affected by rain. If I report this to BT, what is the probability of them doing anything about it?
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AArdvark

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Re: Does very heavy rain improve your DSL signal?
« Reply #11 on: August 30, 2015, 07:56:04 PM »

If I report this to BT, what is the probability of them doing anything about it?

Advanced Probability Theory ..... I think we would need Weaver's mathematics skills to work that one out. <jk>

[Note: I have no idea what it is either  :D ;) ]
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Weaver

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Re: Does very heavy rain improve your DSL signal?
« Reply #12 on: August 31, 2015, 10:21:43 PM »

I think _Weaver_ would need Weaver's _former_ mathematical skills - ashamed to say I only got a B in my A level, which I one reason why I never had the remotest chance of becoming a career  theoretical physicist. That and too idle.
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AArdvark

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Re: Does very heavy rain improve your DSL signal?
« Reply #13 on: August 31, 2015, 10:44:28 PM »

Your 'B' Trumps me. The job is yours. :lol:

I am sure I typed 'Mathematical', the problem is probably not using the 'usual letter sequence'.  :D
Auto-correct then takes a random guess, as that works 'so well' usually doesn't it!.  ::)

[Random signal delays between Brain & Fingers  ??? ]
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