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[KyleMac]

On my SNR graph it's stepping instantly between ~6.5 and ~8.5. The screenshot shows it happening so far this week at Monday 10am to 10pm, Monday 11pm to 11:30pm, and Tuesday 9am to 8:30am. On the weekend it only had a few blips. Last week it was only happening at about 4:30pm to 7pm.

Considering the rough regularity and the instant steps it's probably interference from something turning on/off? We can't find anything in the house that causes it. We do have powerline adapters but unplugging them during an SNR drop doesn't make it go back up.

Errors go up when SNR drops but they still seem low. The stats on the homepage equate to only 0.05 ES/hour.

[burakkucat]

On my SNR graph it's stepping instantly between ~6.5 and ~8.5.

<snip>

Considering the rough regularity and the instant steps it's probably interference from something turning on/off?

Yes, it certainly looks like something switching on and then, sometime later, off. As you have already checked for anything obvious in your home it must, therefore, be due to something in the external environment, through which the pair pass.

[Weaver]

I have this problem on one of my lines, but with the upstream only though, and I don’t have a regular 24-hour pattern but I do have fixed upper and lower levels, which latter two features are I am assuming true for you. What is really bizarre in my case is that I have four lines and the phenomenon only appears on one line.

I haven’t managed to identify the source, but I’m certain that it’s outside the house.

[tubaman]

Almost certainly electrical interference when it starts and stops as suddenly as that.
Your very precise sync rates do suggest that your line is banded unfortunately, and it could well have been this interference that has done it.
All I can suggest is walking the cable route back to the cabinet when it is happening and seeing if anything thing obvious is going on.
 

[KyleMac]

What's bothering me is it does seem to be related to stuff in the house but not a single device.

For example, it'll start when someone turns on a smart TV but it won't stop when it's turned off (and completely unplugged). It will stop a few hours later when someone shuts down their PC and goes to bed. It'll start when I wake my desktop from sleep but stop when someone calls the landline (the Gigaset base station is on the network).

These could be coincidences as they're usually only within a 5 minute window but it keeps happening. My current hunch is it's one of the network switches.

I have an RTL-SDR dongle that can do direct sampling down to 612khz and it can pick up AM radio but it doesn't seem to be suitable for detecting REIN. Putting the antenna directly next to any electrical devices doesn't pick up anything. Does anyone have more experience with RTL-SDR?

[Alex Atkin UK]

Just out of curiosity, have you tried leaving the powerline adapters disconnected long-term just to eliminate any potential that they are having "some" impact, even if its not the main cause?

[burakkucat]

I have an RTL-SDR dongle that can do direct sampling down to 612khz and it can pick up AM radio but it doesn't seem to be suitable for detecting REIN. Putting the antenna directly next to any electrical devices doesn't pick up anything. Does anyone have more experience with RTL-SDR?

Sorry, no.    I have an Icom IC-R5 which I use when checking the 300 - 600 kHz frequency band for any emitters of abnormal radiation.

[KyleMac]

Here's an image of the SNR from the Zyxel VMG8924-B10A aligned with the activity of a UniFi AP AC Pro.

The rough correlation is obvious on the graphs but it's not due to any single device. Or is it all just a coincidence?

I've tried unplugging the AP completely and it's not the cause by itself.

Just out of curiosity, have you tried leaving the powerline adapters disconnected long-term just to eliminate any potential that they are having "some" impact, even if its not the main cause?

I haven't done it yet because they're mostly used to connect older ethernet printers. It would cost about £300 to get WiFi cards for all of them but it would eliminate all AV1 homeplugs. I want to do this as it's an easy upgrade but it's expensive for a hunch.

However once they're gone there's still two AV2 plugs bridging two UniFi AP AC Pros between buildings. I'd need to replace them with some mesh thing or another AP in uplink mode. I'm less keen on doing this as it's more money and might not work anyway. AV2 plugs also have the option to avoid VDSL interference which I assume means they stick to 30Mhz+.

If powerline adapters can cause these trailing SNR adjustments then I'm willing to try. Videos I've seen of interreference usually show it being pretty instant and stopping as soon as they're unplugged.

[tubaman]

... It would cost about £300 to get WiFi cards for all of them but it would eliminate all AV1 homeplugs. I want to do this as it's an easy upgrade but it's expensive for a hunch...

Going off on a tangent, but have you considered something like this for your printers - https://www.tp-link.com/uk/home-networking/wifi-router/tl-wr702n/
I use them on YouView boxes to make them wireless and they are great. That particular model is end of life now but they regularly appear on eBay etc. They can be USB powered which is also convenient.
 

[vic0239]

I use these TP-Links too, they are very versatile devices. Great for devices with no Wi-Fi or those unable to support more up to date encryption protocols.

[KyleMac]

Going off on a tangent, but have you considered something like this for your printers - https://www.tp-link.com/uk/home-networking/wifi-router/tl-wr702n/
I use them on YouView boxes to make them wireless and they are great. That particular model is end of life now but they regularly appear on eBay etc. They can be USB powered which is also convenient.
 

I know about these but I'd rather go the cleaner route of installing internal WiFi cards.

I have some serial to ethernet adapters from Brainbox and they recommend using the Nanos to link to WiFi but I noticed some Chinese copies have added WiFi so I'm thinking about them too.

The cheapest solution is probably Pi Zero W's acting as bridges but they would require extra maintenance.

If unplugging the powerline adapters instantly changed the line stats I'd immediately spend the money to replace them. What's holding me back is they might not be the cause.

[KyleMac]

I was moving APs around testing if I could bridge buildings with UniFi's wireless uplink and since putting them back the baseline FEC errors have increased but the spikes have decreased meaning the SNR has been stable.

Could the PoE cables for the APs be interfering with VDSL? Or just another coincidence?

EDIT: Typically as soon as I post this the SNR drops.

[burakkucat]

Could the PoE cables for the APs be interfering with VDSL? Or just another coincidence?

As you surmise, just another coincidence.

[KyleMac]

I accidentally unplugged the modem which reset the scale of the graphs. I didn't notice this pattern in the errors before. It looks like they peak about every 12 minutes.

[burakkucat]

  Hmm . . . Something peculiar is occurring. But I can't think what it might be.