ST546v5 - errors mounting quickly

I'm finding that, once I use DMT to set my line sync speed and noise margin, those figures are held, even into the evening. (Surprising; I wasn't expecting that). However, this seems to be at the expense of many more line errors (FEC, CRC and HEC). The errors seem to mount quite quickly. Is this an indication that I need to reposition the SNR even further upward, so that I operate at an even lower linespeed? I'm currently on 4128K bps and an SNR of 10.5dB.

Has interleaving been switched on? If so, then the FEC error figure is of no consequence.

Eric

Yes, interleaving on my line has been in operation for a month or two, and therefore well before I bought my ST546v5.

Of no consequence? Well, it begs the question as to whether the 546 (and DMT) reports the errors AFTER error correction. I assume that it does. And what about the CRC errors?

I seem to be accumulating millions of FEC errors and thousands of CRC errors quite quickly - nearly 2 million in about 24 hrs. Maybe I just need to push the SNR upward a tad more, to bring down the sync speed?

These are my results after nearly 6 days uptime

In reply to:

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Bandwidth (Up/Down) [kbps/kbps]: 448 / 3,456
Output Power (Up/Down) [dBm]: 12.0 / 19.0
Line Attenuation (Up/Down) [dB]: 24.5 / 51.0
SN Margin (Up/Down) [dB]: 20.0 / 9.5
FEC Errors (Up/Down): 920 / 132,507
CRC Errors (Up/Down): 50 / 734
HEC Errors (Up/Down): 32 / 665

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The CRC and HEC errors are after the FEC errors are corrected due to interleaving
If the FEC errors stay low I might request interleaving be removed although I don't game so probably no point

OldJim,

Interesting. Your line attenuation isn't too far different from mine (mine's 50dB, according to this ST546). But whereas you're clocking up just 132K FEC errors in 6 days, my FECs are around 2M in about 24 hrs. I notice that your line sync speed (presumably, that's what you meant by 'bandwidth'?) is 3456K bps, though. Mine's currently 4128K bps. So, maybe I DO need to make a further adjustment, to bring my speed down?

Of course, I accept that error counts don't depend on attenuation alone but more on the character of the interference on the line. In that respect, comparisons are perhaps useless.

Read this after my post of 16.20 hr.

Using DMT, I pushed my noise margin up another notch and then did all the usual button-pushing in DMT, to store and reboot. That rendered me 3840K bps at 11dB. But then just as I was about to close DMT, everything got cleared and it disconnected (it still being only 16.46 hr in the afternoon). I then reconnected and repeated the button-pushing in DMT but it failed to resync and instead I got an error message from DMT saying something along the lines of "too many errors" .... "cannot resync", and again it disconnected. A third attempt was successful, however, and I've ended up with 3872K bps at 11dB. I exited DMT sharpishly, just in case that peculiar timeout/clearing occurred again.

@Meditator
Even when I was synching at 3968 I didn't get a lot of crc and hec errors but it wouldn't hold overnight when snr dropped to under 5db

if you think 2 million is a lot try ignoring 300 million a day

look at your tones are any below 0? whats the lowest snr reported as is it a negative number?

I can set my snr target to 6 for example with the lwest tone at say 4snr and there will be enxt to no errors, a tone then later (usually after noise burst) is stuck on a negative number and errors will climb fast.

Likewise I coul dhave a target of 15snr and if a tone get sstuck below 0 no matter how much snr is on the other tones errors go up fast. If the CRC remains low then dont worry about it.

My line has taken to resyncing at approx 10pm every night with modemoption00=58 (having been fine at this setting for weeks) because of crazily high CRC rates, think I've fixed this by using one of JinxterX2s tricks i.e setting the option to '10' and doing a manual resync/reboot at 10pm, this gives me a sync in the region of 4800-5000kbps but a massively reduced error rate, I think because your getting all the Gaps in one go, if you see what I mean.