Broadband Related > ADSL Issues

Afternoon burst of errors

(1/6) > >>

Weaver:
The other day, I noticed that one of my ZyXEL VMG1312-B10A modems’ Johnson graph-plotting function was showing a large burst in errors per unit time during the afternoon of the 7th. Janet had a workman at the house for that time interval although the time he was here was much longer than the duration of the interference period. When I asked her about it she said, "but he wasn’t on the same mains supply!", which is good thinking, and is true, because the site where he was working, an outbuilding, has its own separate mains feed, it isn’t fed from the house. I explained to her the concept of RF interference and had to tell her something about what radio frequency EM energy is, then I think the penny dropped.

Anyway, I have some pretty pictures below, one of "FECs" and one of "CRC errors".

Could someone help me understand how these images were arrived at? I’m being really, really stupid again.

There’s also the question of how/where the PhyR L2ReTX protocol fits in and how it affects the definition of these terms - ie pre- and post- L2ReTX recovery vs protocol ReTX timeout.

FECs:




CRCs:



And what kind of tools and what kind of badness in those tools (if any) causes RF interference like this?

Normally the CRC rate is between 0 - 4 per time interval, so very clean. And once again I have forgotten what the unit time interval is in these Johnson graphs; Burakkucat and friends must have reminded me at least twice already - so I will need yet another reminder if you all would be so kind and then I’ll write it down somewhere prominent. Trying a search of the Kitz forum proved too confusing.

Alex Atkin UK:
What was he doing?  I work on the assumption that any kind of inductive load can spit out a ton of RF on various frequencies.

burakkucat:

--- Quote from: Weaver on August 09, 2021, 09:58:11 AM ---And once again I have forgotten what the unit time interval is in these Johnson graphs; Burakkucat and friends must have reminded me at least twice already - so I will need yet another reminder if you all would be so kind and then I’ll write it down somewhere prominent. Trying a search of the Kitz forum proved too confusing.

--- End quote ---

Unless it is shown as otherwise then, with such plots, I would always assume the time quantum is "per minute". (Per second and per hour would be somewhat illogical.)

The question to ask yourself is "What is the sampling rate?" and the answer is "Once per minute". The counters are read once per minute and then the delta between two adjacent reads of the counter in question is then is plotted.

Weaver:
I didn’t explain my confusion properly at all. My apologies. I should have asked about the exact definition of CRCs and FECs.

As for the time quantum being ‘per minute’, that is my best guess having zoomed in on the graphs of certain suitable, moderately ‘busy’, alternating 0-1, 50% duty-cycle datasets.

@Alex - he was repairing a floor that was damaged by a flood caused by sheep-attack. No I’m not joking, sheep who were scratching rubbed on a plastic water pipe and managed to damage a connector or something, causing a huge flood. Several floorboards were cut out and replaced and then (amazingly good-looking) fake tongue-and-grooved plastic ‘wood’ was laid over the whole floor.

It is our first experience of a sheep-attack. Donkeys also scratch their backs on things. Janet has purchased some strong, stiff wire fencing material to keep sheep (and haggis) out of where they shouldn’t be.

tubaman:
Serious RF noise like that can be caused by a badly suppressed motor in an electric drill or the like. Another possibility is a badly suppressed petrol engine - from a standalone generator perhaps?
 :)

Navigation

[0] Message Index

[#] Next page