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Thread ID: 75570	2007-01-03 11:06:00	Is there such thing as a good ADSL FILTER?	Ninjabear (2948)	Press F1

Post ID	Timestamp	Content	User
512402	2007-01-04 07:46:00	When I bought filters, DSE sold me Nokia ones from "out the back", they were not an officially stocked item (but the price was the same). They said that the ones on the rack were not as good as the Nokia, however as they now sell DSE branded ones I have no idea if they are the Nokia or not. I use a single Nokia in-line filter modified to filter the whole house "phone" line, with only the router connecting before the filter. Works just fine for me. I do the same with a Dynalink MF28A inline filter. However this is a topic worthy of further investigation, as doing a bit of Googling does show ADSL line filters/ POTS splitters, ranging from simple 1st order with 6db per octave attenuation up to 6th order filters with very sharp roll off and somewhat lower cut off frequency than the simpler ones. The frequency range for the high frequency ADSL is 30KHz to 1.1 MHz, whereas the phone audio only has to go up to nominally 3.4KHz. A quick measurement on the Dynalink filter, (but without a POTS simulator in circuit), indicates around 10dB attenuation at 30KHz, and a cut off frequency at -3dB of 10KHz, whereas a 6th order filter (equivalent to connecting 3 filters in series) is quoted on one site as 43 dB at 30KHz. So, I'd say that filters do indeed vary, and a "good ADSL filter" may well give better results in some conditions. I can't find the site mentioned above now, but here are some others of interest: www.midcom-inc.com www.accesscomms.com.au www.adslnation.com I could not find any specifications for the "popular" line filters sold here like the D-Link, or the Dynalink, so there seems no way to compare them with other specifications except by setting up to measure them.	Terry Porritt (14)
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