Permanent increase to downstream SNR on FTTC

[#1]

---

@dleholt wrote:

@outcast what router do you have,

---

My router is pfSense firewall software running on an Intel J3455 CPU Gigabyte motherboard with two Ethernet ports.

I have always used separate external modems.

For a modem with adjustable SNRM for VDSL, my recommendation would be a  DrayTek Vigor 130

or for the most awesome VDSL modem (without adjustable SNRM) then the  DrayTek Vigor 167  is hard to beat.

You should be able to get either of those (second hand but like new) for £20 to £30 on eBay.

You should be able to connect either of those modems to the WAN port on your Hub-2

.

[#2]

The question which needs to be asked and answered is why if the line is unstable why will the BT system not allow a 6dB (or higher) target SNRM to be set to deliver improved stability?

Is the order being rejected for some other reason?

[#3]

For any products past ADSL, (FTTC, SOGEA) Manually changing the SNR margins through BTWholesale just gets rejected right away. It's only use is for ADSL Lines.

It would be ideal if we could, as far as I am aware they simply just get rejected unless it is an ADSL line.

Not sure the exact reason for this, but yeah, just a no go sadly.

[#4]

---

@dleholt wrote:

I can’t hear any noise on the phone, although I’m unable to do the proper quiet line test given I only have an old pulse dial telephone (yes, really!) and hence can’t select the option. The Hub Two (and phone) are plugged directly into the master socket fitted with a faceplate filter.

---

1. How far away from the Master Socket is the telephone ?
2. How far away from the Master Socket is the Hub Two ?
3. Is there any house telephone extension wiring attached to the back (inside) of the removable filtered faceplate ?
4. Have you tried plugging the Hub Two into the TEST socket (behind the filtered faceplate) ?
5. Do you use any 'powerline' adaptors to extend your LAN around your home ?
6. Is there any other electronics or electrical equipment near to your Master Socket ?

Given that you're on FTTC broadband, and that the UK PSTN landline telephone system will be decommissioned from the end of 2025,  have you considered 'upgrading' your phone service to VoIP (phone calls via broadband) ?.

You will probably save money by 'upgrading' your Plusnet FTTC (VDSL and phone) contract to SoGEA (VDSL without phone) and then migrating the landline number to VoIP,  and if you want to carry on using your landline phone from 2026 you will have to 'upgrade' in the coming months anyway !.

On my home setup, I had as near perfect broadband and phone wiring as it was possible to achieve, but when I finally changed my line from FTTC to SoGEA, my modem's maximum achievable sync speeds immediately improved, and the frequency of modem dropouts pretty much disappeared.

You can still use your old pulse dial phone with a VoIP service if you use an appropriate adaptor to connect the phone to a LAN port on your router,  there are several instructional videos on YouTube of how to achieve that, for example -

YouTube : How to use rotary phones with VoIP 

YouTube : How I Connected A Rotary Phone To VoIP Phone System 

.

[#5]

---

@LexLex2020 wrote:

For any products past ADSL, (FTTC, SOGEA) Manually changing the SNR margins through BTWholesale just gets rejected right away. It's only use is for ADSL Lines.

---

Hi Lex,

Thank you for the clarification / knowledge share.

So if that mechanism cannot be used on FTTC / SOGEA, are there other leavers / buttons to be pulled / pushed in circumstances where a sticky DLM configuration is leading to poor stability?  Is this where line profile (stable / standard / speed) comes into play?

Surely BTw must have a vector for managing this space?

[#6]

I suggest that the next thing for @LexLex2020  to try on BTw,  is to ask whether the line can be artificially banded ?.

By applying a capped (banded) profile on the maximum sync speed negotiated between cabinet and modem,

this would have the side effect of increasing the noise margin to a more stable position, that's not overridden by DLM.

Assuming that the line doesn't continue to deteriorate, then this (if possible) would pretty much be a permanent 'fix'.

There are some modems/routers (although I can't immediately remember which ones), where you can (using Telnet commands) set your own modem's maximum negotiable sync speed (for the purposes of making the line more stable).

.

[#7]

FWIW, from a brief search, the following modem/routers appear to have the capability of user limiting max sync rates -

• DrayTek Vigor 130
• Billion BiPAC 8800NL
• TP-Link Archer VR600 (or VR2800, depending on firmware)
• Zyxel VMG Series (e.g., VMG1312-B10A, VMG3925-B10B)

Disclaimer - do your own research to check whether I'm correct on the above before spending any money !

.

[#8]

Thanks for that, I’ll do some research. Unusually the connection has been up for almost 2 days now at 3dB. I’m starting to wonder if it’s weather related. To answer some of the other questions; both Hub Two and phone are plugged into a master socket 5c which OpenReach changed a couple of years back, and there are no extensions. We do use a single powerline adapter from the Hub Two to my son’s PC. The only other electrical item nearby is a Raspberry Pi.

[#9]

What make / model is the powerline adapter? Some are know to interfere with VDSL signal stability …

[#10]

They are el-cheapo Tenda PH6 AV1000 that I bought because my previous Devolo ones would overheat and stop working. I could probably try swapping them back if I can find them.

[#11]

I've had about a dozen Devolo's of various models, and never saw any signs of overheating, or heard anyone express concerns about overheating before - I have now !.

I avoided using a powerline adaptor anywhere near my modem to eliminate the possibility of radiated RFI on the modem or incoming landline cable,  instead ran a 5m ethernet cable (between carpet and skirting board) to the next nearest mains socket, where my master powerline adaptor is plugged in.  I thoroughly tested whether the powerline RF signal in the mains wiring has any effect on my modem line stats and error rates, and in my setup there is no indication of any interference.

.