[bimbobarbie]

Hi

Hope someone can help

I am connected to the internet via a netgear dg834n wireless router but the SNR keeps dropping.

I can connect via two laptops and the SNR does nor drop however when i connect using my desktop the SNR margin starts to drop after several minutes and continues dropping until connection cannot be made.

Currently I am connected with the desktop and a laptop and can see the SNR dropping from 6 to 3.3 and the continues to drop, however id I switch the monitor display off the the SNR jumps back up to 6.

I understand that the problem is with the desktop but what can cause this, I have replaced the psu as I thought that was the problem but that did not solve it.

I am now thinking that it might be the ethernet card but why would the SNR jump up when the monitor is switched off or is it the monitor that may be causing the problem.

Any help will be much appreciated

Bimbobarbie

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SNR? Signal to Noise Ratio?

is this a CRT monitor? how close is the monitor to the router? are you talking about the SNR of the wireless connection or the wired connection? do you by chance have enough tin foil available to make a suitable "Brain Wave Espionage Disruption Helmet" (i.e. tinfoil hat)?

Edit:merged the duplicate topic from the office forum to this one in the networking forum

[dsenette]

SNR? Signal to Noise Ratio?

is this a CRT monitor? how close is the monitor to the router? are you talking about the SNR of the wireless connection or the wired connection? do you by chance have enough tin foil available to make a suitable "Brain Wave Espionage Disruption Helmet" (i.e. tinfoil hat)?

Edit:merged the duplicate topic from the office forum to this one in the networking forum

[bimbobarbie]

hi dsenette

No it is not a CRT monitor it is about 2ft away from the router and the connection is wired to test, but it also drops when the computer is switched on any ideas what it could be

[dsenette]

so if you turn your monitor off the SNR (again assuming signal to noise ratio) goes back up?...does it do this if the network cable on the desktop isn't plugged in?

[bimbobarbie]

if i unplug the ethernet cable from the desktop the SNR was 5.3 then when cable disconnected jumped to 6.3 and when monitor switched off with ethernet cable still out SNR went to 6.4 then replaced ethernet cable and SNR down to 5.4.

So am unsure whether it is the monitor or the ethernet card, however monitor does have an effect but so does unplugging the ethernet cable, any ideas

Yes dsenette you are correct SNR is signal to noise ratio

[bimbobarbie]

by the way if I switch off the desktop completely the SNR jumps from 5.8 to 8.1 and when switched back on again dropped from the 8.1 to 5.3 and will move up and down a couple of points then after a period of time will continue to drop

[dsenette]

this is going to be a difficult test but.... is there any way where you can plug the desktop into a power outlet that's on a different circuit in your house than the one that the router is plugged into? like on a second floor or across the building/house whatever?

[bimbobarbie]

hi dsenette

Have done as suggested and plugged desktop into a different circuit using an extension lead and results as follows

When switched desktop off the SNR was 8.1 now with desktop plugged in and switched on the SNR dropped to 7.6 and as yet is remaining steady if it stays at that and does not drop it will be fine what do you think it is and is there anyway to get round it other than having a long extension through the house

thanks

[dsenette]

obviously the extension cord isn't a good idea...


this is obviously an electrical instability of some sort....

you could have something grounded in the case that shouldn't be....or something could be going wrong with your power supply...or it could be the wiring in your house specifically

it SEEMS like whatever is causing the "electrical disturbance" is turning your desktop into an antenna

[bimbobarbie]

Hi dsenette

Thanks for the help I have replaced the power supply unit and it made no difference however I did have the router and the desktop plugged into a power surge extension maybe that could be the problem I will try the desktop straight into a different outlet on the same circuit and see if that works.

I have just noticed that the SNR has dropped to 4.4 so it has not fixed the problem what do you think may be the problem with the desktop. By the way had to stop part way through this reply as the SNR dropped to 3.5 then switched off the monitor for a minute and the SNR up to 7.8

Any help much appreciated

[dsenette]

to be honest i have no idea what's going on hehe which shouldn't be a surprise...this one's funky

did it take longer for the SNR to drop with it on the extension cord than before or no? if you're introducing some form of "static" into the power signal of the house itself then being on a different circuit will just make it take longer for the static to propagate through the rest of the circuits...they're all connected somewhere...

this would probably be a HUGE pain in the butt to do...BUT it would be interesting to see if you were to take all of the components out of the case of the desktop and hook it all up separately outside of the case on a piece of cardboard on the floor and see if that makes the symptoms go away

[bimbobarbie]

hi dsenette

It took about the same time but it can vary and can be alriht for hours but will eventually drop unfortunately I am not that confident about taking everything out of the case.

This problem has occured since May and everything has been checked regarding ISP and line.

Why does it not occur using the laptops if it could be static based as these are connected to the same electrical circuit

Any other ideas

[dsenette]

IF it's electrically based interference (which it might not be...but that's my only guess at the moment because an LCD monitor shouldn't be giving off any EMI) then it would be generated by something faulty somewhere....if the laptops aren't faulty then they wouldn't cause interference

[dsenette]

i think the issue is either with the router or the desktop (i'd lean towards the desktop at the moment)....

what's the make/model/age of the router?

also do you have a radioshack near by? maybe get one of these and put it on the power cord of the desktop and see what happens

[happyrock]

starjax suggested changing the wireless channel that the router is using

because the monitor is somehow involved also try putting the Snap Choke Core on the computer to monitor cable

can you borrow/buy a Wireless G USB Adapter and try connecting to the router using it instead of the wired connection...
nojoy....
This list is not exhaustive but common culprits could be:

• A current imbalance between two power carrying conductors (Earth leakage fault).
• Faulty thermostats (Central heating, Immersion heaters).
• Electrical power supply units (Laptops, Routers, Plasma TVs).
• Industrial/Commercial power usage (Electric Railways, Electric fences, Electric motors).
• Decorative electrical items (Christmas tree lights, Touch lights).
• Security systems (PIR lights switching on and off).
• Digital Communication Receivers (Satellite and Freeview set top boxes).
• Internal power and telecoms cables run close together at the End User.
Strong signals from nearby amateur radio, CB, FM and other transmitters are picked up by long wires running through the house: electric power wiring, telephone cables. alarm system wires

try to track down the source of REIN..( repetitive electrical impulse noise )

If you suspect there is something interfering with your broadband, get an AM/MW radio and tune it to 612Khz. If you hold the radio next to an LCD screen for your pc as an example you would hear a distinct noise. This should fade away if you move the radio a quarter to half a meter away. Hold it by your modem/router and you'll hear the DSL signal.

If you get a distinct noise enveloping a larger area, then this may be picked up by your router causing an SNR problem (or even drop of sync). By using the radio you may be able to get an idea of where the noise is coming from. Switch the suspect appliance off & retest your DSL connection. By distinct noise you're looking for a clear buzz, whistle, clicking etc. White noise or a general shhhhh noise is less likely to be the cause of the problem, same as any radio broadcast.

Be aware that any noise heard on the radio is not always affecting your DSL connection, and you may still have REIN issues in the area which will not be picked up @ 612Khz as REIN is often notoriously difficult to pin-point. This method can be a bit hazy so don’t rely on it completely by any means.

Xmas lights are a classic cause, as are noisy electrical appliance with a long length of wire which acts as an antennae. Sometimes you can cure it with a ferrite sleeve (that small cylindrical thing you normally see along your monitor cable which doesn’t seem to do anything) which you can get from electrical suppliers such as Maplin.

Edited by happyrock, 24 July 2009 - 08:12 AM.