2017-12-12

It's official, ADSL works over wet string

Broadband services are a wonderful innovation of our time, using multiple frequency bands (hence the name) to carry signals over wires (usually copper, sometimes aluminium). One of the key aspects of the technology is its ability to adapt to the length and characteristics of the line on which it is deployed.

We have seen faults on broadband circuits that manifest as the system adapting to much lower speeds, this is a key factor as a service can work, but unusually slowly, over very bad lines.

It has always been said that ADSL will work over a bit of wet string.

Well one of our techies (www.aa.net.uk) took it upon himself to try it today at the office, and well done.

He got some proper string, and made it wet...


It turns out he needed salty water to get anywhere.

A 2m length...


And the result - it works!!! Not even that slow (3½Mb/s down) though slow uplink. Don't dare touch the string though...


So, there you go, ADSL over 2m of literal "wet string". Well done all for testing this. It shows the importance of handling faults that seem to just be "low speed".

As a bonus, fit tin cans to both ends and you get voice as well as broadband on the same wet string!

62 comments:

  1. Great post, would love to hear more detail.

    Voice-Over-Mullers could be huge, you could corner the market

    ReplyDelete
  2. Apologies, someone posted and I clicked delete by mistake:

    Firstly, that's awesome, I love it. Your office is basically a hackspace.

    Secondly, congrats, you're on the front page of Hackernews.

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  3. ADSL is now considered like old tech but actually it has evolved incredibly during the years and has solved uncountable engineering challenges.
    This post was really surprising and interesting to read.

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  4. Yes conductor will make wave guide, though to improve could put insulator between them to get them closer. Even better to twist the salty wet strings and insulation between them to have less leakage (salty wet twisted pair)

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  5. Wonderful. Now telcos will install string as a cost cutting measure to increase profits.

    ReplyDelete
    Replies
    1. Especially in rainy climates.

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    2. You say it as if that's not an upgrade what most of them already use

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    3. Finally, the salty tears of their customers will be put to good use..!

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    4. I believe someone said on an internal chat "the salty tears of Amber Rudd" at one point. But marmite was also suggested as an electrolyte.

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    5. Gives a whole new meaning to a 'ropey' broadband service.

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  6. That takes me back to my days in the Royal Signals!

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  7. How did you pin the rj45s with limo wet string? How long did you soak the string for? Is there a step by step procedure I can do? How can the string carry 5 volts? What about ground? How did you twist the string? Wire twisting, well you know all this I am sure you got it all figured out and are able to show the procedures in an in depth article.

    ReplyDelete
    Replies
    1. Well we could, but also the pictures show most of the answers (crock clips, etc).

      Delete
    2. Also, where does the 5 volts come in?

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    3. In this case, no "RJ45" (or 8p8c) connecters were used. The connection from the DSLAM went to a telephone socket, then to an ADSL filter, and then to an RJ11 cable which has had one end cut off, and stripped, to connect directly to crocodile clips. It was these croc clips that interfaced to the string. At the other end, the test leads of the xDSL testset were designed to connect onto clips.
      In this test, there was no voltage present on the pair - this is commonly called a "dry pair". No ground was connected, as DSL runs over the A and B leg of a pair and doesn't need to care for the ground. Performance could have likely been improved by twisting the pairs.

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    4. "Dry pair" on a "wet line".

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  8. So how come the $#@! ADSL lines go down whenever it get's wet.

    Eventually I gave up on the damn thing and went with fiber and haven't looked back since.

    Alas, for various reasons I'm forced to play with it again.....

    ...because somebody has deployed it in a wet place.

    ReplyDelete
    Replies
    1. Not enough salt in the rain obviously.

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    2. Corrosion on the copper line. I had that every year, it was so annoying.

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  9. Great. Now you're gunna give OpenReach ideas...

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    Replies
    1. Saw Openreach pulling in blue rope only last week. When asked, they said it was to improve internet speeds.

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  10. As you posted, people say the ADSL will work over "A piece of wet string". Your picture shows he used two pieces of wet string. ADSL will continue working (badly) with one leg disconnected so I suggest further testing is required!

    ReplyDelete
    Replies
    1. Once both legs dried out, the JDSU did attempt handshaking when only one leg was wetted. It never completed negotiation though - I think the attenuation on 2 metres of this particular type of string is just a bit too high.

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  11. They were too busy wondering if they could, to think if they should...

    Lol jk this is awesome, suddenly I realise what internode in Brisbane are using.

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  12. Doing it like as Telefónica from the catacombs...

    Test it with dental floss under a solution of propanol with silica gel.

    Probably the results will be better.

    ReplyDelete
  13. Literally faster than the ADSL2+ service to my home.

    Bandwidth (Up/Down) [kbps/kbps]: 443 / 2,258

    ReplyDelete
    Replies
    1. At least yours is better than Talk Talk could provide to my mother. Her downstream was capped at 1024 Kbps. (Now with A&A, and running at 11 Mbps, over the same line.)

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  14. Is that string BABT approved telephone equipment? ;p

    ReplyDelete
    Replies
    1. No red triangle on the string, so I'm sure it's approved apparatus.

      Delete
  15. By remarkable coincidence, here's some ethernet over barbed wire: http://www.sigcon.com/Pubs/edn/SoGoodBarbedWire.htm

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  16. Can you lads test VDSL2 over the same string?

    ReplyDelete
    Replies
    1. Given the losses on ADSL (see https://twitter.com/0x47DF/status/940634277967990784 for bingraphs) with a large number of bins going unused, it looks unlikely that a VDSL sync could be attained on this string currently.

      Delete
  17. Is this the new PPPoWS protocol?

    ReplyDelete
  18. Here's 50+ mbps VDSL over banana...:

    http://nordenstam.org/17/bananledere.jpg
    http://nordenstam.org/17/banansync.jpg

    Cheers! ;)

    ReplyDelete
  19. Dont't let the ITU see this - they'll want to invent a wet-string-encoding-profile with gratuitous incompatibility...

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  20. Take a look to PJON, it works through the human body :)

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  21. Q: What do you do when your internet connection fails?
    A: We piss on it!

    ReplyDelete
    Replies
    1. Piss sounds like it could work quite well. There may be some health and safety issues around testing this however.

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  22. That's not the kind of wet string I was picturing when seeing the url for the first time. Good job though, well done ! :)
    Now.. off to find the other kind...

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  23. Well that's the best use I've ever seen of those awful Herman Miller chairs. £1,000 each of uncomfortable un-ergonomic rubbish.

    ReplyDelete
  24. I see the BBC picked up on it as well - as a news story!

    http://www.bbc.co.uk/news/technology-42338067

    ReplyDelete
  25. Awesome experiment! As someone who installs/repairs ADSL2+/VDSL2/GPON on a daily basis, I absolutely loved reading this! So how far from the DSLAM are you actually? Just curious how much loop length that wet string adds. Also did you take any CRC/CV errors? Next you'll have to strap the tip and ring together and test the resistance of the wet string.

    ReplyDelete
    Replies
    1. We have a DSLAM in the office, so almost entirely wet string involved. Not sure were we are with errors yet, I think some real work got in the way.

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    2. Well that answers my question about resistance over wet string: not all that conductive. I won't be taking this solution back to the board meeting! Guess we will have keep experimenting with magic spells!! That's what the customers seem to think after our sales tell them "it's all wireless now...."

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    3. It is a tiny little ZyXEL one, and I forget how much, sorry. Google it :-)

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    4. An Alcatel Lucent 7330 VDSL2/ADSL2+ DSLAM costs about US$100,000. Those can feed 384 pairs per DSLAM.

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    5. Depending on the maker, model, features, and number of ports a DSLAM is a few hundred US dollars to a couple hundred thousand US dollars. I've seen two-port SOHO models and then there's the carrier grade stuff David addresses.

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    6. The copper leg from DSLAM to desk is, at a rough guess, around 15 metres as we had to come from the other side of the office where the DSLAM lived, although loss on 15 metres should be negligible. And yep, plenty of CRC errors there. If there's a way to balance the pair better, and twist it, these could perhaps be reduced a little.

      Delete
  26. Quiet day in the office was it lads?

    ReplyDelete
  27. As if kids weren't spoiled enough nowadays, getting a tablet and/or smartphone before they are 5 years old. Now they're gonna want string broadband installed in their tree-forts too. ;)

    ReplyDelete
  28. Fix yer snr and the uplink speed will be better. Try something with vectoring and let it cook for a month or two and see if it gets better? That would mean keeping the string wet for a month...the HST 3000 is kind of stacking the deck though ;) Looks like fun

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  29. For your next test please match the string impedance to 600 ohms.
    Well done....

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  30. Haha! I'd wager a bet that wet string works a lot better than the rotten old phone lines that provide my ADSL of sorts.
    Good one!

    ReplyDelete
  31. Sounds like a new revenue stream for BT...

    ReplyDelete
  32. 3 1/2 megs? That's better than AT&T can do in a Red State!

    ReplyDelete

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