Draytek router playing up on ADSL line, BT one OK?

Many moons ago we started to have trouble with line drops on our ADSL service. BT discovered a fault on the line some 60 metres away, which meant it was under the reinforced concrete road outside. I was offered a service via a pole that was to be set up.

I refused this, and instead bought a second-hand modem by 2-wire, otherwise badged as a BT 2700HGV, and which had been reflashed to stop BT interrogating it.

The 2-wire had been designed for use in the US on long lines, and was supposed to have superior software when it came to handling noise. It totally ended the interminable dropouts that we’d been having.

It could be that your two routers differ in their capability of handling noisy lines.

There’s a 2700HGV modem on eBay for not very much, if you fancied a punt, other sources are doubtless available.

Is that actually <24Mbps ADSL, or VDSL (FTTC)?

On a BT Homehub 5a (Lantiq VRX200 series chipset) I've found connection stability can vary quite a bit based on VDSL modem firmware. Some of them support vectoring, others don't, and stability seems to be a bit of a mixed bag - some are 'good', newer can be worse than older. It also seems to vary based on the match of the modem to the cabinet (eg Broadcom modem with Huawei cabinets which contain Broadcom chipsets). I'm using OpenWRT for which the firmware download is a separate file:

I would expect that BT/PN have deployed the most compatible/stable modem firmware for your connection (they can remotely update their routers). Draytek probably haven't done updates like that so it could be less stable, however it's worth installing any updates that are available.

I would not expect this to be a hardware fault.

I just use the ISP routers to get the best VDSL performance, and put my stuff behind them.

Theo

Have you still got a phone connected to that line and if so have you checked the line for noise (no crackles etc. when listening on the phone). When I had ADSL line drops it was always a noisy line that could be determined by listening to it on my phone

I don't know if the BT quiet line test still works (or works with another supplier) but... Dial 17070, and select option 2 for the quiet line test. There should be complete silence on the line. Try the phone in the master socket perhaps with everything else disconnected.

Google AI summarises what I was going to write " On a noisy ADSL line, the synchronisation ("sync") speed during training is reduced to create a larger signal-to-noise ratio (SNR) margin, ensuring a more stable, albeit slower, connection. "

Are you sure that synchronisation is not masking the problem in that after so many disconnects the BT router you have now plugged in is just sync'd at a lower speed. .

Yes, this seems a common issue with Draytek routers on BT lines. There is a thread about it admitedly on VDSL here :-

Dave

One thing I have noted is that ADSL front ends can go screwy after a big thunderstorm.

Another thing I have notes is that it took IDNET and Openreach 4 goes to finally get me a good ADSL line .

And then I moved to FTTP.

I think you may be blaming Draytek for something else. Maybe someone nearby has a strong ham radio. Maybe the line runs past a welding shop.

My Draytek has DSL status in its diagnostic section. You probably need to start there and also look at SNR on upload/download. If Plusnet are resetting the line its because the DSLAM at the far end has noted high noise levels and reduced DSL speeds accordingly.

Also if where you are is anything like here, there have been several episodes of major rainfall, and any undergrounds may well be getting flooded.

I've had an ADSL2 failure here.

Around 9PM every evening, the ADSL2 modem would drop sync.

Now, I happened to have an analog TV set at the time, in the room, and there was a "herringbone pattern" on the screen. I went around the room, and turned off PCs, until turning off one specific PC, made the herringbone pattern in the background of the picture, go away.

So I knew which PC was emitting electrical noise on the mains wire. I used the TV as a collector of evidence.

Turning off that PC, also allowed the ADSL2 modem to operate properly at 9PM without any issues.

I changed out the defective PSU, bought another and installed it, and no more problems. No herringbone pattern on the TV set. No modem LEDs flashing a failure in the evening. It has operated for years since then, never dropping sync.

You know there is a problem with the modem design, when the design is attempting to "double-filter" the DC fed through the barrel jack. This suggests the designer knew the noise floor wasn't very good, and so they threw as many solutions at it, as they could.

If you look at the PCB layout, there are some electrical connections on the PCB that are very carefully laid out. Implying again, the designer knows there is a noise issue, and so everything they can think of, is included in the design.

The ADSL 1 modem before it, as it does not have the same ambitious datarate in the design, the noise floor isn't as perilous on that one. That thing was like a rock... even though the datarate the telco allowed was a s*it rate :-) We were promised "up to 5Mbit/sec" at the time, and the ADSL1 modem was policed on the telco end to not go past 3 Mbit/sec. The ADSL2 device is running 15Mbit/sec.

Paul

Are you sure it is ADSL and not VDSL?

Where are you? I could lend you other Draytek routers, either older or newer, or spare PSUs. I'm near Thetford in Norfolk.

Many of the 2-wire/2700 modems have an interesting intermittent failure mode. At some point the manufacturers started using a larger sized flash memory than had originally been used. The only problem was that they left the most significant bit of the address floating. The address would be randomly high or low depending on the relative leakage currents of the input transistors. At manufacture this would determine whether the software got programmed into the high or low half of the memory. So long as the leakage currents did not vary too much all was good. Sometimes, a nearby static charge or random variation in leakage currents perhaps due to humidity changes could cause the floating address input to change state, depriving the modem of its software.

John

Yes there are versions of firmware designed for lines that need a more conservative speed optimisation to remain stable for long durations. So it can be worth checking what you are running.

Fascinating! All I can say is that ours worked splendidly for the time we had it, and its performance on our noisy line was exemplary. The 2-wires were very popular at the time for those with noise issues.

Yes, they were generally very good. I had a few (*) in various places. I tripped over the floating address bit problem when reflashing the firmware. Probably only a small proportion of the units had sufficiently symmetric leakage currents to cause a problem.

• Thinking back - I may have mis-identified the problematic modem. I am sure it was made by 2-wire, but it might have been branded as Speedtouch or similar. They were supplied by BT and I got mine from eBay. John

Come to think of it I could GIVE you a Cisco SOHO router that was, in its day, excellent

Can you get into the router to read error logs?

Long ago in pre-history I had line problems with BT and could look at the error log and tweak some of the modem settings. Then again we wore animal skins and hunted with clubs.

Cheers

Dave R