| reply to Bicephale
Re: The customer's own wiring Centralized Filtering
An important parameter in case of high attenuation
is wiring, persons living in appartments are bound
to use "distributed" filtering while those who are
in a private home can have "centralized" filtering
if they choose to. This section refers to the 2nd
option, it hardly applies to appartment situations
unless the landlord happens to be cooperative. My
text is intended at those who can call Bell to get
an "NID" installed outside of the building and i'm
suggesting they do if it's not there already since
the best-case scenario one can dream of is when he
has the opportunity to add a filter/splitter right
at the heart of his NID box - then a CAT-3 twisted
pair cable (or better) to create a clean DSL path:
NID Filter/Splitter (The Yellow Module on Top)
Ideally, the internal circuit will look like this:
Alarm-compatible "POTS Splitter"
Shielding
Sometimes centralized filtering doesn't suffice in
presence of nuisances though, that's why i'm about
to describe how i ended up trying to control noise
caused by kitchen activity! I had been collecting
Error Rate (aka "noise") curves for a while when i
thought of superposing some daily records and then
i finally noticed there were quiet vs busy periods
emerging: noise was linked to human activities so
i got the idea to check if it didn't come from the
kitchen by turning off the wireless phone but that
failed; it felt clueless so i turned on the other
appliances by pure curiosity and bingo! At 1st, i
couldn't tell which peaks i caused so i decided to
do it repetitively, at the begining of every hour;
starting from there, most of the noise which i was
creating became easily identifyable as it detached
in terms of time/level from almost any background:
%20.PNG)
Man-made Noise (Graphic Generated using GNet BB0060B MoDem/Router & 'DMT v2.x' 3rd-Party Utility)
I already had implemented centralized filtering at
the demarcation point so it wasn't clear what more
could be done and most specially beyond of it. It
seemed an inspection of Bell's wiring was in order
and i knew i couldn't count on their low wage sub-
contracting staff to do it extensively, somehow...
It didn't take long before i finally put my finger
on it: decades ago Bell had installed flat wiring
closely to the electrical power panel; many moons
later someone must have completed this messy setup
by packing all of those loose ugly wires together:
Improper Phone Wiring Installation
My 1st action was to separate Bell's wiring but it
wasn't enough so i started to experiment with ways
to cure the rest through shielding. It wasn't too
clear what was required in order to shunt magnetic
and electric fields in this situation so i started
my work with two sections of strong 1" square iron
tubing... This was quite some involving challenge
which required heavy handcrafting - not to mention
the fact that Bell's line had to pass thru it all:
 %20&%20Home%20Lines%20.JPG) %20&%20Home%20Lines%20.JPG) %20&%202nd%20Ground%20Bloc%20.JPG)
Final Centralized Filtering & Indoors Shielding
Anyway, my shields worked but it still didn't stop
all of the noise so i went outdoors and discovered
that Bell's flat cable also happened to follow our
PVC Power conduit and passed under Hydro's counter
as if it wasn't bad enough. It was impractical to
add more iron tubes so i prefered sleeves instead:
Ferro-magnetic Metal Sleeves
Here are the same shielding sleeves once in place:
Outdoors Shielding
Although highly innovative, i think any technician
who can excercise his judgment should be satisfied
with this shielding approach and most specifically
the part where sleeves are used as these happen to
be non-intrusive and go off easily after a test...
In any case, this graphic feels like thought food:
%20.GIF)
Comparative Man-made Noise Curves
The final conclusion here is avoid close proximity
to power conduits at all costs if that's possible;
there are no more excuses now for Bell's employees
to layout a dry-line, etc., in such a lousy way!!!
N.B.:
The last graphic has a red bar reaching beyond 200
errors per hour, i didn't cause it so i can't tell
where it came from but this strongly suggests that
other noise sources were still an important factor
which shielding didn't appear to cure efficiently.
A loose (high-impedance) shunt across the line can
produce such a disruption. Actually, it turns out
that i do expericence disconnections due to a loud
noise sometimes and it's momentarily attenuated by
"hammer pulse dialing" number 9 a few dozen times!
 |
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| Note:
Somehow the 'Tweaks' thread to which i link at the
begining of a related one was interrupted. Please
use this link to obtain a complete access instead:
Tweaks, Bicephale, 2007-Aug-27 |
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| reply to Bicephale
I don't mean to spam meaninglessly but this should be stickied. That is one hell of an informative post. |
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| Thank you! I had a FAQ in mind when i started this but i changed my mind...
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| 
Toroïdal Choke |
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| said by Bicephale:And now, the final touch... this looks cool. Does it really reduce a significant amount of noise on the phone line? |
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 GuspazGuspazPremium,MVM
join:2001-11-05
Montreal, QC
kudos:16
4 edits | Most of Bicephale's changes seem to be focused on eliminating the 60hz AC interference, although I could be mistaken.
Bicephale: It looks like that Bell cabling is both pairs in one cable. Would you get less interference if you replaced it (at least the inside wiring) with shielded twisted cat5e or cat6 (or to get insane, cat7 cabling, which shields both the cable AND the individual strands within it, so double-shielded) cabling? Or would that have less shielding? |
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