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ADSL connections in Sydney, Australia seem to either not work, or work slower when it's been raining or after it's been raining.

I tried googling for ADSL and rain, and I got a lot of user-generated content, but not many reliable sources.

Does rain affect ADSL speed and reliability, or am I imagining it?

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it could be that more people are using the internet and stepping on each others bandwith – ratchet freak May 27 '12 at 11:11
I remember hearing from an engineer that water and moisture can affect phone lines if they aren't insulated correctly, might be a good direction to search for an answer from. – rjzii May 27 '12 at 23:39
@RobZ: as an anecdotal evidence I can confirm that, have had problem after very intensive rains until badly insulated copper has been replaced by fiber-optics. – vartec May 29 '12 at 11:44
@vartec - Progress on reference materials - Systems Studies Reference Library note the section on why cables are pressurized. – rjzii May 29 '12 at 14:45
Is this more appropriate for Electronics.Stackexchange? – Sklivvz Jan 15 '13 at 18:03
up vote 6 down vote accepted

From AT&T Southeast FAQ -

Can weather affect my DSL connection?

Answer: Yes, it can. The primary cause of poor connections due to weather are moisture related. Since ADSL technology is electrical in nature, all of the exposed equipment can be affected by moisture which is an excellent conductor of electrical current. This, combined with the fact that the properties of water allow for "seepage", gives greater exposure to equipment that would, otherwise, be impervious to other weather conditions.

While it isn't a research article, it is an answer provide by a company who provides DSL service on their FAQ page, so I would think that there is some credibility behind the answer.

Additionally, I have programmed ADSL modem device drivers in the past and I do know that ADSL does self adjust its transmission rate in order to maintain reliable communications. So if the weather is causing communication errors, then the ADSL modem will try slower data rates until it reaches a rate where reliable communications can be maintained.

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It's not really about ADSL, which is the technology responsible for connection from the switchbox to your home ("the last mile"), but more about the broadband relay links. These can be either wired (typically in densely populated areas) or wireless using microwave transmission relays (more typical in less populated areas).

Water particles, such as rain cause microwaves to scatter, thus causing path loss.

Rare events of temperature, humidity and pressure profile versus height, may produce large deviations and distortion of the propagation and affect transmission quality. High intensity rain and snow must also be considered as an impairment factor, especially at frequencies above 10 GHz.

This effect is so well known and documented, that it's actually used as a measure of rainfall's intensity. See "Rainfall estimation using microwave links" or "Identification of Dry and Rainy Periods Using Telecommunication Microwave Links".

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I'm with you that a microwave link would be affected by rain, but it would surprise me if @Andrew, living in a city of 4.5m people, has a microwave link between him and any substantial part of the Internet. (Perhaps Andrew can confirm he isn't living in some secluded outpost?) – Oddthinking May 29 '12 at 13:20
@Oddthinking: valid point. As I've commented on the question, for effect on wired version, I've got only anecdotal evidence, and I haven't seen any studies on badly insulated copper wires ;-) – vartec May 29 '12 at 14:15
@vartec - Proper documentation is out there somewhere, odds are it's going to be in an engineering text as opposed to a scientific journal though. – rjzii May 29 '12 at 14:42
@Oddthinking I was living in Woollahra at the time, which is close-ish to Bondi Beach. – Andrew Grimm Jul 19 '12 at 13:16
While the effect on microwave propagation is true, water also affects poorly installed copper wire connections and may well have a big effect on the sort of signal propagation properties relevant to the high frequencies of ADSL. – matt_black Jan 13 '13 at 14:22

If water gets in the wires it can play havoc with even plain old 56k modems, let alone ADSL modems. I grew up in a dry climate, there were certain systems that couldn't even support a 2400 baud connect in rainy weather. We yelled and yelled at the phone company but by the time their repair guy looked at things the wires had dried out and the problem was gone.

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Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

Please provide some references to support your claims. Your anecdote doesn't cut it. – Oddthinking Nov 9 '15 at 23:04
@Oddthinking How am I supposed to provide links proving what I experienced, especially as this was back in the BBS era? – Loren Pechtel Nov 9 '15 at 23:08

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