[HN Gopher] So good, it works on barbed wire (2001)
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So good, it works on barbed wire (2001)
Author : voxadam
Score : 150 points
Date : 2024-05-23 16:20 UTC (2 days ago)
(HTM) web link (www.sigcon.com)
(TXT) w3m dump (www.sigcon.com)
| westurner wrote:
| > _In summary, the barbed wire had zero impact on signal quality.
| The signals went through perfectly undistorted. The only thing
| the barbed wire did was impress the heck out of Broadcom 's
| customers.
|
| Next time you look at a transmission line, I hope you'll focus on
| the big four properties: characteristic impedance, high-frequency
| loss, delay, and crosstalk. These properties determine how well a
| transmission structure functions, regardless of the physical
| appearance or configuration of its conductors._
|
| FWIU from "The Information" by Gleick, Shannon entropy Shannon
| started out with digital two-state modulations on wire fences
| mmastrac wrote:
| Even with my electrical engineering degree, four years of hard
| math, signals courses and understanding all of this at an
| abstract level, it all seems magical to me when it works in
| practice.
|
| Thanks to all the tireless engineering of all the folks that
| manage to abstract this all away so we get clean zeroes and ones
| at the other end.
|
| I'm definitely a digital, logical, bits-type-of-guy.
| ch33zer wrote:
| I certainly don't have your credentials but wasn't the point of
| the articles that it looked flashy while proving nothing about
| the capabilities of the chip?
| treflop wrote:
| Pretty much.
|
| If you took undergraduate EE, you would learn most of how to
| pull off Broadcom's trick when you learned transmission
| lines: https://en.wikipedia.org/wiki/Transmission_line
|
| Cool applications, but probably one of the more boring
| chapters IMO...
| helsinkiandrew wrote:
| Surely, although iron has 1/6 the conductivity of copper, even if
| severely rusted there's far more metal than the wires in a decent
| ethernet cable, and far more separation between them
| bee_rider wrote:
| They mention the distance in the blog post.
| Dwedit wrote:
| Has anyone successfully run a faster protocol on Thinnet Coax
| Ethernet cable?
| amluto wrote:
| It has the wrong impedance for MoCA, and any long split-off
| sections might cause nasty reflections, but other than that,
| MoCA (possibly through an impedance matching transformer) ought
| to work fine.
| cyberax wrote:
| You can run 1GBps on it. There are companies that sell hardware
| for it, even specialized multi-port switches.
|
| They are mostly used to retrofit the old CCTV infrastructure
| for newer PoE-based systems. It's typically called Ethernet-
| over-Coax. E.g.: https://www.nvtphybridge.com/ or
| https://www.dualcomm.com/collections/ethernet-over-coax/prod...
| nurple wrote:
| Is it not also powered via common-mode voltage? Love how coax
| engineers are always stacking frequencies, including 0Hz.
| ssl-3 wrote:
| Simplified, Thinnet is just RG-58, and RG-58 is just coax that
| has a characteristic impedance of 50 Ohms, and 50 Ohm coax
| works just about like any other impedance of coax as long as
| the termination impedance is correct (or the length between
| terminations is 1/4 wavelength), and the attenuation is not too
| severe.
|
| One can send the whole RF spectrum down a single length of
| coax.
|
| The little pinkish-copper wires in your wifi gear are just
| coax. SATA cables: Also coax. Uncompressed HD video over SDI?
| Also coax.
|
| (But you asked about successes, not theory. I've run 5G
| cellular services through thinnet wire. Does that count?)
| mixedCase wrote:
| In the same vein of interesting experiments on weird cables:
|
| ADSL on wet string: https://www.revk.uk/2017/12/its-official-
| adsl-works-over-wet...
| bee_rider wrote:
| Makes you wonder what's going on when you _do_ get a crappy
| connection.
| Loughla wrote:
| Honestly, before we had municipal fiber, I'm pretty sure our
| connection was wet string. Rural living does have its
| drawbacks.
| nick7376182 wrote:
| What is the impedance of a gopher's teeth?
| Epa095 wrote:
| The string is dry.
| Simon_ORourke wrote:
| My gawd, now I've seen it all! That's one step up from digital
| transmission via pigeon.
| kqbx wrote:
| Reportedly, ADSL can work even if there is a short (~5mm) gap
| in one of the conductors (because of capacitive coupling).
|
| source: Someone said this on reddit so it must be true
| https://www.reddit.com/r/networking/comments/7jj7ap/comment/...
| exmadscientist wrote:
| If one wire in the pair is still connected, it's not really
| working because of capacitance (which is ~nil at 5mm), it's
| working because _diff pairs are amazing_. The remaining
| signal level on the single wire was probably enough to keep
| the receiver happy (at ~10kBaud in the Reddit post, versus
| the design ~100MBaud), and so, you win.
|
| Any time you can spare the pins & wires to go differential,
| and have the slightest hunch you might need it, just do it.
| Diff pairs work!
| jwilk wrote:
| Discussed on HN:
|
| 2017: https://news.ycombinator.com/item?id=15908107
|
| 2021: https://news.ycombinator.com/item?id=29440681
|
| 2024: https://news.ycombinator.com/item?id=40387318
| jp57 wrote:
| Tl;Dr - ethernet.
| ksherlock wrote:
| I was expecting the barbed wire / telephony story.
|
| https://www.atlasobscura.com/articles/barbed-wire-telephone-...
| DeathArrow wrote:
| But does it work on wet rope?
| mindslight wrote:
| Why does the demo title within the image say "Gigabit Ethernet"?
| Is that a marketing lie of what they had hoped to eventually
| achieve, with the actual demo running 100mbit? Or was the same
| demo repeated for (what would become) 1000Base-T?
| kaycebasques wrote:
| Great story. Seems like a prime example of "any sufficiently
| advanced technology is indistinguishable from magic." In this
| case the barbed wire was a sleight-of-hand trick.
|
| One day I'll dive into networking technology. It's fascinating to
| me how going down the OSI model layers results in such different
| goals, requirements, and constraints.
| moffkalast wrote:
| If you think this is impressive look up Powerline ethernet, that
| shit is bananas. Though it's probably its own protocol with far
| more error correction.
| suroot wrote:
| I'll beat a bit of a dead horse with this one. This is why I'm
| not a big fan of water/pipe analogies when it comes to the study
| of electricity, electromagnetism and somewhere down the line
| electronics. While I understand early pioneers used "fluid" as a
| kind of hypothesis, I do not think they used them as analogies. I
| think they were trying to derive what was happening by comparing
| and seeing if their observations matched their line of thinking.
| All analogies break down relatively quickly the moment you
| attempt to work upwards from first principles (as we presently
| understand them which for all intents and purposes is "good
| enough" given we got many things to work just fine.)
|
| The reality of the situation is far more impressive and
| engrossing if we attempt to truly get a handle on what is
| happening. Only then can we have a clearer idea of the nature of
| things like impedance and where/why/how the formulas that we use
| are derived from.
| snakeyjake wrote:
| That analogy has gotten an uncountable multitude of people,
| including children, into electronics where "working upwards
| from first principles" is either not practical or impossible.
| jaredhallen wrote:
| True. And many people don't care about the details. My wife,
| for example. She just wants to understand enough to wire up
| her derby cars. The water metaphor is perfect for those
| situations.
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