Intermittant Modem, possible power issues?
 

Good morning all at CF! :)

I have a little, but growing issue with my interweb connection, more and more often, browsing the internet has become slower and slower, sometimes while my browser says "waiting for www.example.co.uk", the send/recv lights on my modem (a VM re-badged ntl 250) do not light up.

When this happens it either times out and I have to refresh (which usually but not always works), or it kicks into gear itself and the site loads. While this has been an issue that has existed (albeit very mildly) since I got VM installed 2 years ago, recently it has started to affect downloads too.

If I go to www.speedtest.net for example, the download speeds spike wildly (And nowhere near my usual 20mbps which until a week or so ago was always my result), and the modems send/recv lights would go out, maybe 3 to 4 times for 3-10 second intervals during the download tests.

I'm not sure exactly what is cuasing this issue, but going by the power levels sticky, I may have found a possible cause, but of course that depends on the info up there still being valid, see below:

Cable Modem Downstream
Downstream Lock : Locked
Downstream Channel Id : 0
Downstream Frequency : 402750000 Hz
Downstream Modulation : QAM256 Downstream
Symbol Rate : 5360.537 Ksym/sec
Downstream Interleave Depth : taps32Increment4
Downstream Receive Power Level : 8.0 dBmV
Downstream SNR : 36.2 dB
Going by that figure, than the sticky, that figure is too high, would I need to call Tech and ask them to have a look at it from there, or is this an engineer only thing? Or, am I being paranoid and there's something else afoot here?

Thanks in advance for the help :)

Re: Intermittant Modem, possible power issues?
 

Sorry to have to tell you this but that power level while not ideal is ok :)

Try a test at http://www.pingtest.net see what it has to say for packet loss and stuff.

Re: Intermittant Modem, possible power issues?
 

http://www.pingtest.net/result/2198093.png

A perfect illustration of what is going on. It was fine (around 20ms) until my modem decided it didn't want to play any more, the send/recv lights go out, and when it comes back on, the result gets destroyed.

Definitely something is wrong, and power issues would be logical as it seems like the modem just cannot cope with sustained use (downloads, or in this case a simple ping test) for very long.

Re: Intermittant Modem, possible power issues?
 

What's the upstream transmit power please?

Re: Intermittant Modem, possible power issues?
 

As requested

Upstream Lock : Locked
Upstream Channel ID : 4
Upstream Frequency : 29200000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 2560 Ksym/sec
Upstream transmit Power Level : 46.5 dBmV
Upstream Mini-Slot Size : 2

Re: Intermittant Modem, possible power issues?
 

Well that leaves a dicky modem or bad upstream signal quality.

I am running with moosed modem initially - post on the newsgroups describing your symptoms, they'll check your upstream signal and if all is good they'll ship you out a new modem. Make sure you change the power supply as well as that can also cause issues.

Re: Intermittant Modem, possible power issues?
 

Ah, I think I may have found the issue.

For some reason, removing a 4dB Forward Path Equaliser (something that has been there since VM was installed), has appeared to have solved the problems.

http://www.pingtest.net/result/2200741.png

https://www.cableforum.co.uk/images/...2009/11/72.png

Well, there goes my theory straight out of the window, as the downstream power actually went UP afterwards to:
Downstream Receive Power Level : 10.5 dBmV
Oops.

Ah well, as long as the problem is gone (and it appears to be), I don't care, thanks for the help though Broadbandings! :-)

Re: Intermittant Modem, possible power issues?
 

Ah, so not a dodgy modem but a dodgy attenuator after all that :)

Pleasure and glad all is working. 10.5dBmV should work just fine.