FTTC Broadband drops during 'phone calls

Hi,
My broadband connection drops during any PSTN ‘phone call, in or out. Most of the time it re-syncs and completes a CHAP sign-on while the phone call continues. On occasion the router is effectively disabled (no more log entries). Test calls have shows the broadband drops anywhere between 15 to 80secs into the call. There is no obvious line noise during these test calls.

My setup:
Service: FTTC 40mb BT Wholesale line.
Cabinet: 800+ metres away with Broadcom 193.144 chipset.
Actual data rate down: 25mb - 15mb due to variable noise margin.
Termination: NTE5 with Mk2 filter. (No extension cabling).
Router: BTHUB5A running OpenWRT 19.07 ( Lantiq chipset).
Telephone base station: Gigaset N300A IP into BT faceplate. No Ethernet connect yet.

My ISP has suggested it might be a faulty filter in the master socket sandwich. I was asked to try a DSL filter dongle plugged into the test socket but had exactly the same broadband drop during a ‘phone call with no automatic re-connection. They are reluctant to book an OR engineer before eliminating all possible customer side problems.

There seem to be 3 possible causes:
1. Faulty DSL filter as suggested by ISP.
2. Some sort of interference build up on the line during ‘phone calls – i.e. A PSTN line fault.
3. Some issue with the OpenWRT programmed router.

Can anyone shed light on the likely causes so I can further this with my ISP?

Thanks

You have tested for 1 and confirmed its not that, 2 needs an OR engineer leaving 3 which needs you to change to an alternate router to see if that resolves the issue. If that does not resolve then that leaves 2 and the ISP has to get some guts and get OR to look at the line. When I had this issue on ADSL it was a line fault.

Edited by kommando (Wed 10-Nov-21 13:00:02)

Thank you kommando. Succinct and too the point.
Will give the alternate router a try.

There is a good chance, if it isn’t a dodgy filter or bridge tap fault, that you have an HR fault on your line. Get your broadband ISP to raise a fault with Openreach. Don’t be fobbed off with ‘this is a voice fault, ring your voice provider’

Does it happen all the time, or just sometimes?
We had this happen every month or so for years, I lost count of the number of visits we had to try and solve it, in the end we got FTTP for internet.

In reply to a post by burble:

Does it happen all the time, or just sometimes?
We had this happen every month or so for years, I lost count of the number of visits we had to try and solve it, in the end we got FTTP for internet.

No this is can be reproduced. The first telephone call will cause a broadband drop within the first few minutes. If you follow up with a second call soon after the broadband may stay up, but try again a few hours later and the broadband will definitely drop again.

Presumably when the master socket faceplate was removed, this also disconnected your extension sockets (if any)?

The other thing I would try is temporarily replacing the Gigaset with a bog-standard analogue handset, and see if the fault still reproduces.

If the Gigaset is not the problem then my *guess* would be some sort of short-to-earth fault, but an exchange line check should pick that up - and this is usually the first thing your ISP or phone provider will try.

In reply to a post by Mwood:

In reply to a post by burble:

Does it happen all the time, or just sometimes?
We had this happen every month or so for years, I lost count of the number of visits we had to try and solve it, in the end we got FTTP for internet.

No this is can be reproduced. The first telephone call will cause a broadband drop within the first few minutes. If you follow up with a second call soon after the broadband may stay up, but try again a few hours later and the broadband will definitely drop again.

Ours would go for a month or two without problems then every phone call for several days, or even a couple of weeks would knock out the internet, at one time I did wonder if it was related to prolonged wet weather and maybe water getting into a joint, whatever, the ISP could see there where problems, but by the time OR turned up it was gone, so there was never a definitive fix, if yours is still ongoing when OR turn up then hopefully they should find the cause.