Hi there, I've only posted once before so far & funny enough what your describing sounds very much like some thing known as REIN as it affects you at specific times. I've copy & pasted this again with some modifications (sorry it's a bit long winded) If you do have a REIN issue I'm afraid it's a bit of a Black art in tracing the source some times but I hope it may be of help (KITZ maby it could be handy as another catagory on your web site ?) here goes...
The effect known as REIN or Repetitive Electrical Impulse Noise.
Anything electrical produces some radio noise/s. It’s just a question what frequency, type of noise, & strength, and then if this combination is something ADSL can hear & is sensitive to.
If you suspect there is something interfering with your broadband, get an am/mw radio & 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 & 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 your looking for a clear Buzz, whistle, clicking etc. white noise or a general shhhhh noise is less likely to be the problem same as any radio broadcast. in the south of the UK you may hear a french radio station from around 612KHz)
Be aware any noise heard on the radio is not always affecting your DSL connection, and you may still have REIN issue in the area which will not be picked up @ 612Khz, 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
X-mas lights are a classic cause, noisy electrical appliance with a long length of wire (now an antennae). Some times you could cure it with a ferrite sleeve (that small cylindrical thing you normally see along your monitor cable which doesn’t seem to do anything) You can get these from electrical suppliers such as Maplin.
Last full blow REIN fault I worked on affected at least 3 customers within an 80m diameter, eventually found it to be caused by a LCD monitor for a pc, this sent a strong REIN signal feed back along the mains cabling affecting the local area. Referring to you previous appointments with engineers, it sounds as their doing exactly the right thing where often we may try & tweak, modify, change something even though no fault is found during the visit rather than say, tests ok so good bye & do nothing. The problem with broadband faults unlike normal phone faults is that we don’t get a means of a test which says the line condition is X so we can then prove it to location Y so we can fix the problem. Broadband is more like take an educated stab at trying this, now what do we get?
An Official explanation of REIN:
REIN (Repetitive Electrical Impulse Noise) is noise from the power network that is induced into the telecommunications network. Normally there is little interference from the two co-sited networks, in certain circumstances however electrical interference can be induced into the telecommunications network causing a degrading of service to the telecommunications end user. It must be remembered that the localising and resolution of REIN problems is not an exact science the information contained in the article is intended as a guide. Your own experiences and local knowledge.
Examples of REIN sources:
• 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.
