Wednesday, 13 December 2017

Please upgrade me to ADSL over wet string

Unsurprisingly, we had a request, which I am sure was tongue in cheek, to upgrade a customer line to wet string as it seems faster than his quite long ADSL line.

Don't say we don't have a sense of humour at A&A, and no, I did not write this myself :-

Thanks for your interest in our latest technology, ADSL over wet string (fibre broadband)!

Sadly ADSL over wet string is not a product we can commercially offer at this moment in time - partly because it's not a product Openreach sell (or list as selling) to their wholesalers, and partly because, well, it's something we did for giggles as I'm sure you know :)

Looking at the loop loss on your circuit, it's currently running at about 48dB. In our tests with wet string, we attained 56dB on a line length of just 2 meters, which is about the range where the DSL signals starts to fade out.

My very scientific estimate of loop loss using wet string gives about -∞dB loop loss on your estimated line length of 3197 meters, which suggests that providing a wet string service to you is impossible given the losses, you would just not get sync.

Our tests took several attempts to raise sync on a wet string circuit, these timed between 5 and 60 minutes depending on local weather conditions ie. whether the air conditioning was turned on in the office.

I must warn you additionally, that the upkeep of these wet string connections is very hard; in our tests, we had to continually re-wet the string approximately every 30 minutes to avoid a complete loss of sync, and this process was always disruptive to the signals.

Perhaps if there's an exchange within 2 meters of your demarcation point, and if it's ever commercially offered as a product by the wholesale providers we buy from, it might work, but at this stage, wet string is sadly not a viable product for all involved. I suspect it may be expensive too - as there will need to be an engineer trained in keeping the string damp should the British weather deviate from it's usual damp and rainy grimness present unless it's made a self-service option, but that sounds annoying to be honest.


  1. “-∞dB loop loss” - wow, that’s infinite gain! Where can I get some of this magic string?

    1. Interesting point, it is usually called loop loss, but usually measured in -ve dB. So yes, technically not loss. Nice one.

    2. You wouldn't want a cable with infinite gain - picovolts of noise at one end would emerge as infinite volts at the other - somewhat uncomfortable!

  2. It seems like some experimentation with plant feeders is needed to see if a 'self-watering-wet-string' could be developed

  3. The solution seems obvious. Mount the string inside a long (and, naturally, water-filled) garden hose. This has the added benefits of shielding the conductor (although I doubt it would pass the backhoe test) as well as providing a convenient demarc (garden tap). Any string faults within the property to be the customer’s problem, although you could start a nice racket with a Special Plumbing Investigation “service”.

    There may be unfortunate seasonal DoS issues during hosepipe bans.

    1. Heavy rain could cause issues if there are string joints all together in a box. You'd get connected to everyone whenever it rained. Some kind of broadcast storm.

  4. @Peter I'd imagine the water in the garden hose would be sufficent without the string depending on the mineral content.

    Is that the next experiment?