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capricorn
23-11-2006, 09:04 AM
The speed at my modem has consistantly been 4160 Kbps,I unplugged the phone from the filter rebooted the modem and got 5850 Kbps, I repeated this several times with the same result. I then left the modem plugged into the filter and plugged the phone into a second filter and piggybacked that into the first filter, ever since I get around 5600 - 5950 Kbps at the modem. The phone obviously degrades the line even with one filter. This may or may not help other people.
I hope it does.

SolMiester
23-11-2006, 09:18 AM
Have you tried just using the 2nd filter, maybe the 1st filter is a dud?

capricorn
23-11-2006, 09:21 AM
Yes I have, both filters are ok.

SolMiester
23-11-2006, 09:25 AM
Yes I have, both filters are ok.

or not, as proved by the fact if 1 filter used, your line speed decreases!

capricorn
23-11-2006, 09:45 AM
I give up, why bother !

SolMiester
23-11-2006, 09:51 AM
erh, just trying to understand why 2 filters gives better results mate. Is 1 not as good as the other, do 2 separate the high and low range better etc.....

However, it is a good call, thank-you for the info.

Terry Porritt
23-11-2006, 10:04 AM
The filters are 'low pass filters', they are made down to a price, and being most likely first order have a roll off of around 3db per octave. This means some high frequency dsl signal will be lost. Two filters cascaded will have a steeper roll off approaching 12 db per octave, so less high frequency signal will be lost.

I find this result interesting. My filter is up in the loft at the phone line junction box, with a cat5 cable to the modem, and it is a modified Dynalink plug in filter, it's not quite so easy to test out two in series, but it would be well worthwhile trying.

I had thought of baluns and things to match the very very nominal 600 ohm phone line to 100ohm cat 5, and quickly knocked up 2 x1:1 transmission line baluns connected to give 4:1 with capacitive dc blockers. The result was inconclusive, I seemed to gain on signal to noise ratio by 2db, increased line loss by 2 db, and ADSL connected somewhat slower :)

martnz
23-11-2006, 01:52 PM
Hi Capricorn,

Great point, and you are absolutely right!

Phone lines are designed to carry voice frequencies, the adsl signal is far more fragile and vulnerable to interference. This is why the speed decreases as you get further from the exchange, and some households can get voice OK, but not adsl.

Other phone devices, double adapters, extension leads, dodgy filters etc can all cause problems and/or reduce speed. It is a great troubleshooting technique to start by unplugging everything from every jackpoint. Even try the modem in different jackpoints, and use a dial-up cable (ie RJ11 / BT) so you can connect direct to the jackpoint with no filter.

If that appears to fix / improve the situation, start plugging stuff back in until the issue re-occurs!

Regards, Martnz

gum digger
23-11-2006, 04:24 PM
Someone one with 2 telephone lines can also check.

pctek
23-11-2006, 05:46 PM
All true.
Pity mine makes no difference with things connected, not connected - whatever.

Poppa John
23-11-2006, 11:44 PM
All true.
Pity mine makes no difference with things connected, not connected - whatever.

Well you DID leave Big City's so called civilisation for deep South country living. Big City + Hi speed adsl versus Country life + Slow adsl. Where would you have a better life??? PJ