aje21_2098 wrote:
I expect you have run out of filters because your first line of problem solving is to replace what are probably perfectly fine microfilters with new ones! Even for problems at the exchange.
Found this interesting post in another forum - I have highlighted the bit which might be of help.
A filter does not completely remove the ADSL signal it attenuates it. Think of it like putting a big fat resistor in the line that only resists ADSL frequencies. Over the range of frequencies the filter operates there will be ranges where more attenuation is applied and ranges where less is attenuated. Lets say for arguments sake that a cheap nasty filter is only managing a 5db attenuation at 25khz then putting a second filter in series with it will mean a further reduction of 5db @ 25Khz through the second filter.
The main problem with cheap filters is that they are basic LC low pass filters that have a very poor roll-off and are not efficient across the full range of frequencies. Better filters have more than one filtration stage so that there is a sharp curve and broad frequency coverage.
Controversially some filters will actually ware out as they use electrolyte capacitors and the electrolyte dries out over a period of time changing the capacitance value. More often however filters fail due to unexplained failure or due to electrical damage from a surge on the line rather than simply wearing out. One reason that people think their filters may have worn out is that the filter worked fine on their fixed speed DSL with plenty of spare SNR margin find they experience problems when re-graded to a Max package or similarly filters that worked ok with ADSL don't work very well on ADSL 2+ as they have poor filter characteristics in the higher frequency bands.
