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First post, by Jo22

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Hello everyone,
This is an uncommon question perhaps, but why are cables for landlines still not shielded?

I fully understand that in the early days unshielded, maybe twisted cabling was cheap and totally sufficient for telephone lines, especially since most buildings had electrical lights, at best, and the RFI problems didn't really exist.

But since the days of acoustic couplers, ISDN in the early 80s and especially DSL in the 90s,
mustn't it have been clear that noise is a problem?

Why didn't telephone companies slowly start to use shielded cables, say cheap coaxial microphone cables?

I mean, DSL is a common application for two decades by now, and people still install cheap, unshielded cables. Just that unlike the early days, they nolonger carry "harmless" 6KHz wide AF signals, but extremely broad RF signals that pollute the radio spectrum up to 30MHz..

Any ideas why this hasn't changed?

Thanks in advance,
Jo22

Edit: I'm aware that old telephone systems strictly speaking had no "ground" connection.
But DSL and ISDN are not like this anymore, I assume.

Last edited by Jo22 on 2020-09-03, 09:52. Edited 2 times in total.

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Reply 2 of 12, by Jo22

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Miphee wrote on 2020-09-03, 09:31:

Money.

That was my first thought, too. 🙁

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 12, by Miphee

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Jo22 wrote on 2020-09-03, 09:52:
Miphee wrote on 2020-09-03, 09:31:

Money.

That was my first thought, too. 🙁

Sorry for the short answer but it always comes down to this.
It's also more complicated to install correctly, it needs proper grounding or it won't work. There is always the possibility of a ground loop while unshielded cables are much simpler and cheaper. Most of the time shielded cables are completely unnecessary.

Reply 4 of 12, by Vynix

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FWIW, it would also be useless if the infrastructure doesn't have shielded cables in the first place

Proud owner of a Shuttle HOT-555A 430VX motherboard and two wonderful retro laptops, namely a Compaq Armada 1700 [nonfunctional] and a HP Omnibook XE3-GC [fully working :p]

Reply 5 of 12, by chrismeyer6

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I have a shielded cable for my DSL model and I'm using shielded cat6 from my DSL/pots splitter in my nid to my network closet. It really helped raise my noise margins on my upload and download it allowed me to get my speeds upgrades and keep fast path. At least where I live the F1 and F2 cables Verizon uses is shielded. When I got my DSL service installed the tech replaced my old drop line with a shielded drop line. I've had my DSL connection for over 5 years now and have had zero issues with it.

Reply 6 of 12, by chrismeyer6

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Belkin and cables 2 go make shielded phone cords for use with DSL service. I have one from each of them and there both very well made and really helped with my noise margins. The Belkin one is more flexible but the cables to go line has a better range of lengths

Reply 7 of 12, by Zup

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Shielding is useless unless both terminals use shielded connectors. I mean that both connectors need to have a connection for the shield AND that connection must be grounded.

I doubt that most phone equipment have those connectors, and I highly doubt that any phone company would shield cables all the way to their hubs.

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Sometimes going all the way is just a start...

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Reply 8 of 12, by chrismeyer6

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I don't know about the rest but I do know that Verizon does use shielded f1 and f2 cables. I was able to pick up a cheap Cisco adsl2+/vdsl2 option card for my Cisco 2600 router and that has a properly shielded rj11 Jack and I have the shield properly terminated at the nid and as well as the jack in my network room.

Reply 9 of 12, by chinny22

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chrismeyer6 wrote on 2020-09-07, 11:50:

I don't know about the rest but I do know that Verizon does use shielded f1 and f2 cables. I was able to pick up a cheap Cisco adsl2+/vdsl2 option card for my Cisco 2600 router and that has a properly shielded rj11 Jack and I have the shield properly terminated at the nid and as well as the jack in my network room.

Sorry about the slight derail but how well does this work? I'm assuming its more because you can then any real benefit.
Asking as have both a 2500 and 2600 in storage with no idea why I'm holding onto them accept they come from when Cisco really were the dogs bollocks

Reply 10 of 12, by chrismeyer6

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It works great honestly. Super stable and reliable I can go months without having to restart the router. I'm sort of using the 2600 as just a DSL modem I have it passing data to my iqrouter. A friend of mine gave me the 2600 and I picked up the DSL card off eBay for 5 bucks about 5 years ago. I know it's way overkill for a 5.88/.863 connection but it was stupid cheap and it was a fun project

Reply 11 of 12, by Jo22

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^Thanks for the feedback!😃

Vynix wrote on 2020-09-05, 12:09:

FWIW, it would also be useless if the infrastructure doesn't have shielded cables in the first place

Exactly. They had 20 to 40 years for adapting it, but nothing changed. Digitizing as such startet in the mid-late 70s, when the X.25 networks were built, as far as I remember..
Don't get me wrong, things "work" still this way. With the focus on "still".
The amount of information exchange drastically increased over the years. At some point in the near future, ordinary twisted pair may reachs its end. 🙁

Edit: Another elegant alternative would be fibre glass. No cross-talks, no corrosion, no radio noise, future proof etc. 😀 But for some reason, this technology is even less likely to be supported on a wide scale than a cheap type of coaxial cable.
For some reason, companies refuse to install it with a passion. And if they do, they do so under pressure only.

Edit: Found something interesting (pro twisted-pair) :
https://www.cablinginstall.com/connectivity/r … cable-revisited

However, the article is very dated (1995).
Also, the last paragraph is very suspicious :

"The tests were conducted at AT&T Bell Laboratories Global Product Compliance Laboratory (Holmdel, NJ) and were sent for certification to the Bundesamt fur Zulassungen in der Telekommunikation, a German organization. The UTP cabling system passed every test, including radiated emissions, conducted emissions, electrostatic discharge immunity, radiated field immunity and Electrical Fast Transient/burst immunity."

The German telephone/internet companies, Telekom/T-Online were holding back modern technology for decades and are defenders of copper wire, in my opinion. Their only success was ISDN, IMHO. If they could, I think, they would turn back time and charge on a per time/megabyte basis.. 🙄

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Reply 12 of 12, by Vynix

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I belive twisting pairs would reduce crosstalk to a certain degree.

As for fiber it's a whole other can of worms, but to me it's a viable option, though it can be a bit difficult to pass through (fiber doesn't bend as easily as copper, and in some cases excessive bending of fiber can cause breakage).

Proud owner of a Shuttle HOT-555A 430VX motherboard and two wonderful retro laptops, namely a Compaq Armada 1700 [nonfunctional] and a HP Omnibook XE3-GC [fully working :p]