D.C. Wetting to reduce ADSL line problems ?
Gaius
Any of the Telco people around here remember "DC Wetting" being used as
a reliability improvement technique on BT lines ?
This is a means of reducing the impact of HR faults by passing a small
DC current through the line at all times (generally a couple of
milliamps). This discourages the formation of oxide build-up at joints,
and the consequent range of disconnection and noise problems which are
well reported on this group.
A friend of mine wired a 15K ohm resistor across the A and B legs of his
flaky ADSL line some years ago, and got an immediate and permanent
improvement in line stability. (No problems caused to the phone line -
15K is not enough to cause ring trip).
I'd have thought that the potential reduction in line fault reports
would have persuaded BT to introduce some wetting current ?
I heard somewhere that some ADSL modem/routers may have the option for
setting a DC wetting current via (undocumented) links on the PCBs. Any
ideas ?
The Natural Philosopher
its a good idea as it will push any rectifiers into a much more linear
region.
I might try that here.
alexd
> I heard somewhere that some ADSL modem/routers may have the option for
> setting a DC wetting current via (undocumented) links on the PCBs. Any
> ideas ?
I've seen this in the documentation for a bit of DSL kit, but
unfortunately I can't remember what brand or model.
--
<http://ale.cx/> (AIM:troffasky) (UnSoEs...@ale.cx)
20:07:13 up 29 days, 20:47, 0 users, load average: 0.15, 0.21, 0.18
It is better to have been wasted and then sober
than to never have been wasted at all
198 kHz
"Gaius" <b...@127.0.0.1> wrote in message
news:MPG.26689c553...@news.zen.co.uk...
Having spent many years on private circuit provision in a repeater station,
I remember the principle very well - it was done with strapping on the
integral matching transformers on the amplifier. The details are somewhat
hazy after all these years, and I can't remember what the typical current
was, but it was certainly only a few mA - quite possibly, as you imply, just
a couple. If anyone's got access to TI A8 K0601 please look it up!
You've really got me intrigued now, and I'll be experimenting tomorrow, er,
later today, with a multimeter and decade box.
--
Martin
Graham.
> understand that the ringing current also helps to reduce corrosion in
> joints in the access network cabling.
>
> Using the phone more for voice calls might therefore be good advice
> ;-)
Many phones draw a few mA from the line whilst on-hook (any phone with a display
and no wall wart has to get power from somewhere)
This thread is probably a spin-off from Gordon's recent one, and I wondered
as he is in the VoIP business whether he actually ever uses his BT line to make calls.
More to the point, does he ever *receive* a call, as the DC polarity will reverse
while the AC ringing current is present which may destroy the diode effect albeit
temporarily
--
Graham.
%Profound_observation%
Gordon Henderson
Graham. <m...@privacy.net> wrote:
>Many phones draw a few mA from the line whilst on-hook (any phone with a display
>and no wall wart has to get power from somewhere)
>This thread is probably a spin-off from Gordon's recent one, and I wondered
>as he is in the VoIP business whether he actually ever uses his BT line
>to make calls.
>More to the point, does he ever *receive* a call, as the DC polarity
>will reverse
>while the AC ringing current is present which may destroy the diode
>effect albeit
>temporarily
For that particular line, yes - it's our home phone line, so all incoming
calls for the house come in on it. The only time I make outgoing calls
on it has been to call 151 or my ISPs support line when the line was down.
BT still appear to test lines overnight - well - force a polarity reversal
- I see this most nights in my PBX logs:
May 28 01:14:51 NOTICE[4614] chan_zap.c: Got event 17 (Polarity Reversal)...
May 28 01:14:57 NOTICE[4618] chan_zap.c: Got event 17 (Polarity Reversal)...
But this thread is intersting - given my recent line issues... It's
something I can easilly try, and I'm sure I can find a spare 10 minutes
over the holiday weekend - don't have the luxury of a decade box, but
I do have a big box of 1/4 watt resistors...
(P = V^2/R -> 50^2/15000 = 0.167 watts)
Gordon
198 kHz
"Gordon Henderson" <gordon...@drogon.net> wrote in message
news:hto4om$2ki1$1...@energise.enta.net...
Points above noted.
With a non-display phone and a DECT, I measured 0.14mA. With various values
of resistance across the line - on U-links on the line side of the master
socket with office side disconnected -
15.2K 3mA
18.4K 2.5mA
23K 2mA
31K 1.5mA
47K 1mA
--
Martin
Gaius
198...@anisp.com says...
> >
> With a non-display phone and a DECT, I measured 0.14mA. With various values
> of resistance across the line - on U-links on the line side of the master
> socket with office side disconnected -
>
> 15.2K 3mA
> 18.4K 2.5mA
> 23K 2mA
> 31K 1.5mA
> 47K 1mA
Any ideas on what current a typical router might sink ? (I'm guessing
that most UK spec router/modems don't have DC wetting at all).
m
198 kHz wrote:
>
> Having spent many years on private circuit provision in a repeater station,
> I remember the principle very well - it was done with strapping on the
> integral matching transformers on the amplifier. The details are somewhat
> hazy after all these years, and I can't remember what the typical current
> was, but it was certainly only a few mA - quite possibly, as you imply, just
> a couple. If anyone's got access to TI A8 K0601 please look it up!
>
> You've really got me intrigued now, and I'll be experimenting tomorrow, er,
> later today, with a multimeter and decade box.
>
hey Martin were you once known as 1500m Long Wave?
Mike
bod43
> In article <77WdnfFa9eF_NmLWnZ2dnUVZ8sydn...@brightview.co.uk>,
Just in case anyone cares:)
I had a look and Cisco seem to support "wetting
current" on recent-ish SDSL routers. No ADSL as far
as google can see.
This is Cisco (several hundred currency units min.)
not Linksys by the way.
198 kHz
"m" <mi...@tiscali.co.uk> wrote in message
news:4C003D3B...@tiscali.co.uk...
Nah, that was my old mate 200kHz. Strong chap, very loud, but always
interesting, and seemingly inherently stable. Seems no-one's heard from him
since Feb '88. ;-)
--
Martin
Graham Murray
> Nah, that was my old mate 200kHz. Strong chap, very loud, but always
> interesting, and seemingly inherently stable. Seems no-one's heard from him
> since Feb '88. ;-)
I suppose he started off light and then went home.
198 kHz
"Graham Murray" <news...@gmurray.org.uk> wrote in message
news:877hmng...@newton.gmurray.org.uk...
Yeah - it was all very well being popular, but he felt a need for more
continuity, or so I've heard it announced.
Graham.
"Gaius" <b...@127.0.0.1> wrote in message news:MPG.266a2106e...@news.zen.co.uk...
I'm not sure any of them do, but it could easily be implemented externally
to the router, an easy way would be to modify a micro-filter
--
Graham.
%Profound_observation%
Graham.
"198 kHz" <198...@anisp.com> wrote in message news:SqCdnQ8FfaQcXp3R...@brightview.co.uk...
Thoo much thbilance dithtortion on R4 LW since that date. As affects all my radios,
it must be their microphone ;-)
--
Graham.
%Profound_observation%
m
I thought he just drifted off (to 198) and was never heard from again.
I seem to remember my very old Pye trannie just had a fixed LW at
200Kc/s (what are these metre things b.t.w)
You will be telling me that speed of light isn't 186,000 miles per
second soon or that no-one uses rods poles and perches (except
fishermen, eastern europeans or caged birds)
Mike
Graham.
>
> I thought he just drifted off (to 198) and was never heard from again.
> I seem to remember my very old Pye trannie just had a fixed LW at 200Kc/s (what are these metre things b.t.w)
> You will be telling me that speed of light isn't 186,000 miles per second soon or that no-one uses rods poles and perches (except
> fishermen, eastern europeans or caged birds)
Tell me more about that radio.
I had one when I was about 7; it had no band that you could see,
but switched to 1500m when the dial was at an extremities.
Wire-frame stand at the back, two disk shaped knobs on the front with
knurling around their faces instead of on the edges making them difficult to grip.
Can't remember much more, it's been 50 years since I saw it you understand ;)
I would love to find an image of it on the Web, does it sound like your Pye?
--
Graham.
%Profound_observation%
m
No mine was a white plastic one (about 6x3x1.5") with a red pull-off
back. Just one big dial on front and teh volume and wave chenge on side.
I haven't got a photo as I gave it to an old colleague who collects such
things.
My first radio was a homemade crystal set (at least a germanium diode
not a cats whisker - I'm not THAT old) with home wound coil and open
variable condenser. Used it at school with radiator as earth and
bedspring as aerial (not old enough for teh springs to move around much
- if u understand) High impedance headset placed in pudding basin to
share sound. Worked fine for top 40 shows!
Mike