"Phone line with 1 broken wire still gets ADSL2"
https://forums.whirlpool.net.au/archive/9yzp5wr3
Anyway, my hat is off to the people who designed and implemented ADSL.
It's a blessing-and-a-curse: too many incumbent ISPs in highly-developed nations used ADSL's ability to run on anything as an excuse to put-off FTTH deployments (looking at you, BT).
Apparently we are due to have BT put in their own fibre in the next few months too. Really don’t understand why they are doubling up the infrastructure.
Hoping for a local price war!
Complicated corporate accounting, carrier incumbency, and weak governments are the core causes. Carriers being publicly traded companies really screws up incentives to fix these problems. It seems to be mostly a binary decision at the top; more profit or better service?
They also did the same, stalling and delaying, insisting on introducing ISDN 64/128kbit instead of going straight to DSL like Holland did.
Maybe a few will recall: San Jose California, in the epicenter of Silicon Valley -- but for some reason Comcast (was previously called *COVID*) -- and you couldnt get DSL in San Jose at the time .... literally down the street from Netflix, and freaking home DSL took YEARS for it to reach our houses...
(My point is that it was ironic that in the heart of silicon valley we couldnt even get DSL due to COVID/Comcast
(Arguably, the real insight here is that the very existence of radio is impressive / unintuitive.)
This means it's symmetrical about ground and thus cancels it's own radiated field (eg doesn't interfere with adjacent lines).
But with one side open there is still a path for AC, which is through the other side and using the ground return.
With this broadcasting of signals down a wire now known, it becomes somewhat unsurprising anything capable of transmitting an electrical voltage & current would be capable of transmitting ADSL. Not knocking their effort though, Arnold and Arnold have always like to demonstrate their knowledge. One of them has a personal blog which can be quite interesting.
I wonder if they have considered trying to adapt an SDR dongle to become an ADSL transmitter?
I have now learned that the WA state utilities commission is pretty interested when providers try to pull stunts like this. You can also dig out useful company contact information from the commission's website.
If your POTS lines are down and the telecom company is telling you a "wet pulp repair" is underway, your phones are going to be down for a while because a bunch of paper-insulated cables need to be manually rewired because they got wet and corroded.
I found this interesting: http://etler.com/docs/bsp-archive/629/629-295-300_I3.pdf - guess it's standard practice to dry out the lines, wrap in cloth, put dessicant and then seal it.
But there's a further point, the problem with moisture in the lines is the corrosion caused by electrolysis, which in turn is caused by the 50V DC on the lines. So even with modern plastic insulation, the copper would be corroded away by any electrolysis.
One last point: Rubber was almost never used as an insulator on phone lines.
Still amazing that it worked at all.
Some modems have special debug modes in that can do this too - then you get to know exactly how many meters along the wire the break is. When you get close, you can hook a resistor to the line and rerun the test and it'll tell you how many meters forward or back you need to go to find the issue.
Pretty easy to track issues down that way.
10km of fiber (with transcievers made for that kind of fiber and distance)... gigabits without any issues.
10km of copper pairs for *dsl? Good luck.
But I defy ADSL to work over something really challenging. Like Telstra copper in Australia.
3.5mb down is faster than my mother used to get from her farm north-west of Kempsey NSW. Though to be fair to Telstra she lived about 30km from the nearest town not 2m like the length of wet string.
This was not outer-whoop-whoop either. Metro Perth.
Telstra. Ya gotta love 'em.
> In addition to the more computer-oriented two and four-pair variants, the 10BASE-T1,[17] 100BASE-T1[18] and 1000BASE-T1[19] single-pair Ethernet physical layers are intended for industrial and automotive applications[20] or as optional data channels in other interconnect applications.[21] The single pair operates at full duplex and has a maximum reach of 15 m or 49 ft (100BASE-T1, 1000BASE-T1 link segment type A) or up to 40 m or 130 ft (1000BASE-T1 link segment type B) with up to four in-line connectors. Both physical layers require a balanced twisted pair with an impedance of 100 Ω. The cable must be capable of transmitting 600 MHz for 1000BASE-T1 and 66 MHz for 100BASE-T1. 2.5 Gb/s, 5 Gb/s, and 10 Gb/s over a 15 m single pair is standardized in 802.3ch-2020.[22] As of 2021, the P802.3cy Task Force is examining having 25, 50, 100 Gb/s speeds at lengths up to 11 m.[23]
* https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Sin...
Including power delivery:
> The IEEE 802.3bu-2016[12] amendment introduced single-pair Power over Data Lines (PoDL) for the single-pair Ethernet standards 100BASE-T1 and 1000BASE-T1 intended for automotive and industrial applications.[13] On the two-pair or four-pair standards, power is transmitted only between pairs, so that within each pair there is no voltage present other than that representing the transmitted data. With single-pair Ethernet, power is transmitted in parallel to the data. PoDL initially defined ten power classes, ranging from 0.5 to 50 W (at PD).
> Subsequently, PoDL was added to the single-pair variants 10BASE-T1,[14] 2.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1[15] and as of 2021 includes a total of 15 power classes with additional intermediate voltage and power levels.[14]
Although last year when I bought Cyberpunk I found that a bit of curry powder sped up the ~70GB download quite nicely.
We discovered we can get "dry lines", basically just rent copper run from site-to-site, nothing on it from local carrier. Slap ADSL modems on each and we got max throughout, at a fraction of the cost. Then we upgraded to SDSL, and that was like hitting the jackpot.
To give it a fair shot, assume the driver and microphone are studio quality rather than the kind you’d find on a 1970s telephone handset. I bet it’d work pretty well.
But the real question would then be: how much of an air gap could you create and still get a connection?
Could you post to HN on an ADSL signal that’s being screamed across the length of the room you’re sitting in?
Presuming you have water pipes to your property, could be easier than digging up roads etc.
Only issue might be if you have a leak and need to shut off your water!!
https://www.theguardian.com/technology/2021/aug/09/uk-launch...
It's used to get the last few metres into the home, e.g. from the boundary to the inside of the house. You put a swept tee in at each end, after the stopcock. Water off, dig down adjacent to stopcock, cut pipe, shove a drinking water rated duct down the pipe through the small port on a swept tee. Shove some chlorine tablets in the pipe and couple up to the new swept tee. Repeat interception at other end outside or indoors, and then use standard fibre cable blowing through the inner microduct, and away you go.
There's a huge amount of disused water pipes in most developed nations which are frequently used, similarly using sub-ducting, and you can run cable through mains - but have to come out every time there's a valve, so practically it's usually cheaper to dig. Where it comes in handy is where there's areas you can't practically dig up, e.g. major roads with old pipes underneath.
Source: Have done a bunch of this for a major UK telco.
Oblig:
https://ec.europa.eu/docsroom/documents/46433
>only 10% of the HDMI RMCD met an acceptable EMC quality of at least 50 dB coupling attenuation
ADSL over wet string - https://news.ycombinator.com/item?id=15908107 - Dec 2017 (88 comments)
The next step would be to mandate fibre cables in all new housing. Along with ONT and Router in one solution.
- https://www.quora.com/Is-cellulose-fibre-conductive?share=1
- https://duckduckgo.com/?t=ffab&q=conducting+polymers+example...
In some cases I would be forced to use a cat-5 or even poor quality cat-3 where two pairs are for ethernet , one pair for A/VDSL and the blue pair for voice/POTS (voip to pots converted)
And of course, if the interference can get out, it can also get in. Which is why Powerline Ethernet can work just fine one day, then suddenly stop working.
Plus the big problem with any ODFM system is that it is incredibly intolerant of wideband interference, eg a series of sparks. The reason being that the band of ODFM channels are fed straight into an A/D converter without channel filters. So each time that wideband interference takes out the system, the modem has to stop and renegotiate each channel from the start.
To any experienced RF engineer, Ethernet over Powerline (or any ADSL system) is a disaster waiting to happen.
