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ADSL2+ microfilters

Tony_W
Grafter
Posts: 745
Registered: 11-08-2007

ADSL2+ microfilters

There seems to be a lot of positive freeback (e.g. here) from people who have changed to ADSL2+ filters from the ADSL ones that come with routers.
The frequency range of ADSL2+ download data transfer goes up to 2.2MHz whereas ADSL stops at 1MHz (see here). As such, ADSL filters may be inadequate to allow the higher frequency bands (1MHz to 2.2MHz) to pass through to the router without reducing the signal level.
Although more expensive, the ADSL2+ specific filters do seem to have improved download speeds, reduced noise on phones and reduced disconnections.
Before I commit extra cash, has anyone had any experience of these?
Tony
4 REPLIES
Community Veteran
Posts: 6,735
Thanks: 12
Registered: 02-02-2008

Re: ADSL2+ microfilters

1. You're being confused by terminology, ADSL filters "should" all be filtering exactly the same ranges and only filter the PHONE outlet not the ADSL one.
2. The ones linked to have a good reputation
In a word ADSL2+ filter is a "rebranding"; nothing more, nothing less.
If you have a faulty filter then those would be a perfectly good replacement.
Tony_W
Grafter
Posts: 745
Registered: 11-08-2007

Re: ADSL2+ microfilters

I have read a little more and as you say, the ADSL output from the splitter is generally unfiltered.
From here:
Quote
The ADSL output from filter (if it has such thing) is generally unfiltered line signal (normal home ADSL devices are not to be bothered with line voltage and voice signals.

I would have assumed low pass and high pass filters and perhaps even band-pass filtering to be required to properly isolate the voice, ringtone etc. and ADSL signals. It appears, however, that it is not necessary.
Tony
Community Veteran
Posts: 6,735
Thanks: 12
Registered: 02-02-2008

Re: ADSL2+ microfilters

Quote from: Tony
I would have assumed low pass and high pass filters

Nope.
Frequencies below a certain level are allocated to voice and above that ADSL; simples.  Grin
Tony_W
Grafter
Posts: 745
Registered: 11-08-2007

Re: ADSL2+ microfilters

Quote from: HPsauce
Frequencies below a certain level are allocated to voice and above that ADSL; simples.  Grin

Yes, that is why I had assumed that a low pass filter would be needed (which it is) to allow only the low voice frequencies through to the telephone system, and a high pass filter to allow only the high frequencies through to the ADSL output. It appears that the ADSL boxes can tolerate having low frequency signals on their input - they probably have a high pass filter on their inputs. Not quite so simples.
[Edit] Actually, come to think of it, the 512 frequency bands in the ADSL2+ signal are frequency multiplexed and therefore would not need a separate filter.