I posted in Consumerwatch this morning click here re my initial delight with Netgear help.
Query here is on BT line test (Nildram is ISP) carried out this morning. They measured the SNR twice in the past week as modem is not synchronising at times (Netgear DG824M) and find it to be 57 which they say should be OK. With my modem router connected it measures 64 and they say this is a "massive" 7db increase in SNR and probably a faulty modem. This is getting a bit too technical for me, does it sound right?
I have been loosing synch most evenings from around 5.00 pm
It depends on what you are looking for. For line communications you are dealing with noise that is already there in the wire or fibre optic line also all the amplifiers that contribute to the noise. Generally the longer the line the greater the noise, this can be overcome with low noise amplifiers, this is backgound noise, the same hissing sound when you listen on a radio without a station tuned in.
If the background noise is for instance 7db then a signal has to be greater than this to overcome the background noise. With data, the signal has to be considerably greater than the background noise to make it efficient, if you have a noisy modem it will have difficulty in hearing the signal in the first place, this of course happens in both directions if your noisy modem is trying to communicate with it's chum at the other end, especially if the line noise is high to start with, this is probably the problem with you becomming unsycronised.
Sorry to go on a bit, but I hope that's explained it without getting to technical.
Signal to noise is a power ratio. In decibels it is 10 times the logarithm of the ratio. The logarithm of 2 is approximately 0.3, 10 times that is 3. The reason we use decibels is that it helps to deal in whole numbers rather than decimals. Therefore every doubling is 3dB. Doubling a voltage gives 4 x power (power is proportional to the square of the voltage), or 6dB. This is why although 64 dB doesn't sound a lot more than 57 dB, it in fact means that either the signal power is 5x greater, or the noise is 5x less.