ADSL USB modem disconnects precisely every 79 minutes or 60 minutes 1

[mmshrink2]

This is a problem that I had a few weeks ago, which dissappeared on its own. It's now come back. Today, it's disconnected 8 times in the past 10 hours, the first 4 times was every 79 minutes (a few seconds short of 80m) and since then it's been happening exactly 60 minutes to the second.
I don't use a router and I'm also not networked.
Ta

 

[G0AOZ]

Does this happen irrespective of the Internet connection being in use, or only when "idle"? So are there any "idle time" settings in the ADSL driver/programme software?

Does it just drop the Internet connection, or do you lose sync with your local exchange as well? I.e. (A)DSL l.e.d. flashes through lack of sync.

Can you monitor DS-SNR and DS-ATTN to see if sigs are varying/plummeting/complete dropout, etc?

If you have low SNR coupled with a high ATTN, then a regular heavy burst of electrical noise could result in a dropped connection. To check for electrical noise or interference try using a small battery operated portable radio. Tune it to a quiet spot between stations on the low end of the medium wave, say around 550KHz, and listen at the time your connection drops. A loud blast of noise in the speaker at that moment could be the cause of your ADSL problem. If appropriate, check household appliances, etc., etc.

ROGER - G0AOZ.

 

[mmshrink2]

It happens even when not idling - i can be in the middle of a download at the time, for instance.
I haven't checked the led flashes yet, I will do so.
Don't you think that the precise regularity of the dropped line would rule out electrical noise/interference from appliances?

Today has been pretty much like the last time that this happened - ie dropping at precise intervals over a period of a few days, and then not being able to connect at all for a few hours. So far, after not being able to connect for most of the morning, it dropped once, and has been okay for the past 4 hours or so. Very strange.

 

[G0AOZ]

Don't you think that the precise regularity of the dropped line would rule out electrical noise/interference from appliances? Absolutely not! Something electronic set somewhere to light up/go off/do something on a regular basis. Somebody away for the Christmas hols for instance, could have set a timer to do something every hour or whatever. Bad electrical contacts can cause a nice big arc which is full of RF interference, which is why I suggested the A.M. radio as a detector...

ADSL connections don't like interference of this type, particularly if you have low SNR/high ATTN. You haven't told us what your figures are like yet. Also tell us if you're using the Master phone socket to connect your modem to, or if there is a fair bit internal wiring and connectors in the house that it has to go through first.

So, when the connection drops whilst you're on-line, can you reconnect immediately or does it take several minutes?

ROGER - G0AOZ.

 

[mmshrink2]

I see your point about interference and regularity.
However, today's log is interesting: I had two dropped lines this morning, and then I had precisely 13 hours without a drop. It just dropped a few minutes ago, 12.53 and 22 seconds my time, after being on since 11.53 and 22 seconds. Very weird, and i can't think of an electrical appliance in the vicinity that would be set to do something every hour, let alone with a precise 13-hour delay.

Please tell me how to check my SNR and ATTN figures.

The modem goes straight into the master phone socket, no complicated internal wiring, and all lines in the house have filters on them,

In answer to your last question, the line is able to reconnect immediately once dropped.
Thanks

 

[G0AOZ]

Checking SNR and ATTN will depend upon the type of USB modem you have, and what the installed software provides in the way of diagnostics. As I recall, Thompson Speedtouch modems can be used with some software called Dr.Speedtouch which ought to give you the required line statistics. Some USB modems may well not be capable of providing this useful info. I say useful info because line quality can play a significant part in how well you can maintain an ADSL connection to your local exchange. It's a bit like a radio station - if you're a long way away from the transmitter, you get a poor signal and maybe you can't always hear what the announcer is saying. So it is with ADSL. Nice short route to the local exchange generally gives you a good strong signal. Low SNR equals weak signal, and means the slightest bit of interference may block your connection. High SNR can often cope with quite a noisy electrical environment. Roughly speaking, anything much below 6dB DownStream SNR is cause for concern. ATTN or Loop Attenuation gives an indication of the distance from the exchange in terms of signal loss. The further you are from the exchange, the higher this figure will be. Over 60dB DownStream ATTN is getting borderline.

Routers usually have the in-built ability to monitor line statistics without additional software. Some routers have more sensitive front ends in their modems than others, so can cope better with poor line conditions. As an example, routers with a Texas T1 AR7 chipset are good with low SNR and high ATTN.

Trying to find the cause of your particular problem appears to be getting harder as it seems your line drop is becoming more sporadic. Is it possible to try another computer or a different USB modem? Or even borrow a router maybe? Given you can be there at precisely the right moment, have you tried the trick with the portable radio yet?

Certainly being able to view the line stats can be very helpful. Once you can do this, make a note of DS SNR and DS ATTN - ignore US SNR etc. (This is UpStream). Now try unplugging each telephone device (and its filter) from the sockets in the house. Re-checking the figures after each one is removed - this will tell you if one of your telephones/filters is/are faulty or causing signal loss. Don't forget the fax machine and any telephone connection for Sky etc. I don't know where you're located, but in the U.K. newer phone installations often have a Master socket with an NTE5 type faceplate. Removing the lower part of this socket not only reveals the "test" socket, but automatically disconnects all other wiring in the house from the telephone line, at a stroke! Putting your modem or router directly into this test socket assures you of no problems from telephone devices throughout the house.

Hope that helps...

ROGER - G0AOZ.

 

[mmshrink2]

Thanks very much for the clear explanation.

My modem is a very basic, generic, bottom of the range piece of equipment put out by the telecomm service in South Africa. The drivers were poor enough to require installation more than once, and there is no accompanying diagnostic software, which makes it impossible to get the data you requested (the ostensible support page gives an apparent downstream "noise margin" of 20.5db but I'm not even sure if this is a "real-time" figure). I'm now wondering if the crappy modem might in fact be the problem.

My service provider (the same telecomm service) informs me that there is no problem with the line itself, and I'm assuming that their evaluation of the line would include signal-to-noise and attenuation checks.

Today, so far, has been without any dropped lines (although I've only been connected for the past 6 hours). It is likely that I won't see the problem again for a few weeks, which is what happened last time (ie frequent hourly drops, followed by less frequent drops, and then apparent resolution). I might have missed the window of opportunity for correct diagnosis this time around - eg the portable radio check - and I may have to wait till the next episode.
In the meantime, perhaps I need to upgrade my modem?
Thanks again, Roger

 

[G0AOZ]

I'm not familiar with the sort of tests that ISPs will carry out, but I doubt they'd be able to deduce SNR and ATTN remotely. During a recent "fight" with one ISP here, they reported the line as being "fine" when in fact there was no trace of an ADSL signal on the user's phone line! This was later confirmed by several neighbours who had also reported problems regarding loss of service to their own ISPs. Problems with both lines and exchange equipment turned out to be the culprits...

An SNR of 20.5dB would be fine, as long as it remains stable and doesn't dive down to 2 or 3dB etc.

Doing a Google for your make of modem may bring up software options which might allow real time stats to be monitored.

Good luck.

ROGER - G0AOZ.

 

[mmshrink2]

I have to say that I'm starting to wonder if the problem isn't some process in my PC that's shutting down the connection regularly.
In my last post i'd been connected without problem for 6 hours. What's happened subsequently is that it disconnected precisely 12 hours after I logged on this morning: ie I connected at 10.58:20 and it disconnected at 22.58:20. It's now 4 minutes past midnight and it hasn't dropped the line this hour (I was expecting a drop at 23.58:20).
This adds a new piece of info to the puzzle, since it's not just happening every 60 minutes (or 79 minutes) relative to an objective starting point, but instead is happening at a specific point in time relative to a personal/subjective starting point (ie the time i logged on). Surely this argues against interference from outside or a low signal:noise ratio or high attenuation, and points to someting intrinsic?
Hope I'm making sense here.

 

[G0AOZ]

Certainly seems rather odd doesn't it... Here's a list of a few things to check out:-

1. Check Event Viewer to see if anything is listed at time of first logon on, and at the time of your Internet disconnect.

2. Check Task Manager for any unusual or unexplained services running.

3. Check Startup in MSCONFIG for any unwanted programmes running.

4. Run a full scan of the hard disk for viruses, trojans, adware, spyware, hacking tools etc. Panda has a good on-line scan which is worth running as well. See

http://www.pandasoftware.com/products/activescan.htm

See what that brings forth...

ROGER - G0AOZ.

 

[mmshrink2]

No dice yet.
Nothing shows up on Event Viewer as being associated with the disconnect times, and Task Manager and MSConfig have nothing new running that I can see. Also clean on spy-/add-ware etc (I didn't run Panda, but used Spybot, Windows Defender, Ewido, and Norton Spyware scan, as well as NAV).
I'm going on holiday for 10 days, and I guess I'll pick up the search again then.
In the meantime, thanks for your assistance Roger, and best wishes for the new year.