DIY filters.

I've got a lot of assorted inductors/... here.
My existing filter isn't quite cutting it (9dB SNR loss on inserting
a DECT/analogue cordless phone (oddly, both the wired phones I tried
were -0.2dB).

Can anyone point me at some filter designs, or the specs for them?


Ian Stirling

On 27 Jun 2005 23:49:43 GMT, Ian Stirling <(E-Mail Removed)>
wrote:

>Can anyone point me at some filter designs, or the specs for them?

the specs are in the G.dmt standard, dslforum.org or the like.

BT's SIN at www.sinet.bt.com has extracts and various impedance
requirements. SIN 346.

http://www.adslnation.com/support/filters.php may be interesting.

the dodgy phone will have to go :-)

Phil
--
Tiscali - dialup speeds at Broadband prices, see
http://bbs.adslguide.org.uk/postlist...&Board=tiscali

AOL - the unlimited ISP of choice for heavy downloaders.

Phil Thompson <(E-Mail Removed)> wrote:
> On 27 Jun 2005 23:49:43 GMT, Ian Stirling <(E-Mail Removed)>
> wrote:
>
>>Can anyone point me at some filter designs, or the specs for them?
>
> the specs are in the G.dmt standard, dslforum.org or the like.
>
> BT's SIN at www.sinet.bt.com has extracts and various impedance
> requirements. SIN 346.
>
> http://www.adslnation.com/support/filters.php may be interesting.
>
> the dodgy phone will have to go :-)

Thanks.
Unfortunately, the dodgy phone won't have to go, I'll have to get it
filtered adequately.
I'll have to put the scope on it to see if it's outputting any obvious
crap.

Ian Stirling wrote:
> Phil Thompson <(E-Mail Removed)> wrote:
>> On 27 Jun 2005 23:49:43 GMT, Ian Stirling <(E-Mail Removed)>
>> wrote:
>>
>>> Can anyone point me at some filter designs, or the specs for them?
>>
>> the specs are in the G.dmt standard, dslforum.org or the like.
>>
>> BT's SIN at www.sinet.bt.com has extracts and various impedance
>> requirements. SIN 346.
>>
>> http://www.adslnation.com/support/filters.php may be interesting.
>>
>> the dodgy phone will have to go :-)
>
> Thanks.
> Unfortunately, the dodgy phone won't have to go, I'll have to get it
> filtered adequately.
> I'll have to put the scope on it to see if it's outputting any obvious
> crap.

Not wishing to rain on your parade, but I hope you are aware that connecting
non-BT approved equipment (in this case your DIY filters) to their network
is subject to prosecution and a *HEFTY* fine if/when they find out
--
(E-Mail Removed)
Reply address is spamtrapped. Remove theobvious for valid e-mail address

"Paul King" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
: Ian Stirling wrote:
: > Phil Thompson <(E-Mail Removed)> wrote:
: >> On 27 Jun 2005 23:49:43 GMT, Ian Stirling <(E-Mail Removed)>
: >> wrote:
: >>
: >>> Can anyone point me at some filter designs, or the specs for them?
: >>
: >> the specs are in the G.dmt standard, dslforum.org or the like.
: >>
: >> BT's SIN at www.sinet.bt.com has extracts and various impedance
: >> requirements. SIN 346.
: >>
: >> http://www.adslnation.com/support/filters.php may be interesting.
: >>
: >> the dodgy phone will have to go :-)
: >
: > Thanks.
: > Unfortunately, the dodgy phone won't have to go, I'll have to get it
: > filtered adequately.
: > I'll have to put the scope on it to see if it's outputting any obvious
: > crap.
:
: Not wishing to rain on your parade, but I hope you are aware that
connecting
: non-BT approved equipment (in this case your DIY filters) to their network
: is subject to prosecution and a *HEFTY* fine if/when they find out
: --
: (E-Mail Removed)
: Reply address is spamtrapped. Remove theobvious for valid e-mail address
:
:

I was of the understanding that your side of the wall is your and not their
network,ie no need for BT approval.

Chris
kick-butt.co.uk

On Tue, 28 Jun 2005 19:25:43 +0100,it is alleged that "Joker7"
<(E-Mail Removed)> spake thusly in uk.telecom.broadband:

<snip>

>
>I was of the understanding that your side of the wall is your and not their
>network,ie no need for BT approval.
>

Technically anything connected to any phone jack that has access to an
outside line in the UK is "directly or indirectly connected to a
public telecommunications system" and therefore should have BABT
approval (note, BABT= British Approvals Board for Telecommunications
and is not part of BT). However, how good their enforcement is I don't
know, I can't imagine them wasting the money in tracking you down for
using a homemade and well designed filter or indeed any piece of well
designed equipment.

OTOH, if you were to build a device that had a failure mode consisting
of connecting the telephone line to 240 volts, (think Arthur Daley
special imports), they probably _would_ expend the resources to track
and prosecute, after the first phone company employee got hurt.

--
There is not the slightest indication that nuclear energy will
ever be obtainable. It would mean that the atom would have to
be shattered at will.
- Albert Einstein, 1932

"Ian Stirling" <(E-Mail Removed)> wrote in message
news:42c09097$0$2046$(E-Mail Removed)...
> I've got a lot of assorted inductors/... here.
> My existing filter isn't quite cutting it (9dB SNR loss on inserting
> a DECT/analogue cordless phone (oddly, both the wired phones I tried
> were -0.2dB).
>
> Can anyone point me at some filter designs, or the specs for them?

My phone causes the ADSL to drop when it rings. I've fitted a second filter
in series and that's solved the problem.

Chip <(E-Mail Removed)> wrote:
> On Tue, 28 Jun 2005 19:25:43 +0100,it is alleged that "Joker7"
> <(E-Mail Removed)> spake thusly in uk.telecom.broadband:
>
> <snip>
>>I was of the understanding that your side of the wall is your and not their
>>network,ie no need for BT approval.

> Technically anything connected to any phone jack that has access to an
> outside line in the UK is "directly or indirectly connected to a
> public telecommunications system" and therefore should have BABT
> approval (note, BABT= British Approvals Board for Telecommunications
> and is not part of BT). However, how good their enforcement is I don't
> know, I can't imagine them wasting the money in tracking you down for
> using a homemade and well designed filter or indeed any piece of well
> designed equipment.

In theory, you require BABT approved cable clips, the way the regulations
are worded.
And indeed I suspect the number of prosecutions for using equipment
marked specifically as not to be connected to the BT network closely approaches
0.

Ian Stirling wrote:
> Chip <(E-Mail Removed)> wrote:
>> On Tue, 28 Jun 2005 19:25:43 +0100,it is alleged that "Joker7"
>> <(E-Mail Removed)> spake thusly in uk.telecom.broadband:
>>
>> <snip>
>>> I was of the understanding that your side of the wall is your and
>>> not their network,ie no need for BT approval.
>
>> Technically anything connected to any phone jack that has access to
>> an outside line in the UK is "directly or indirectly connected to a
>> public telecommunications system" and therefore should have BABT
>> approval (note, BABT= British Approvals Board for Telecommunications
>> and is not part of BT). However, how good their enforcement is I
>> don't know, I can't imagine them wasting the money in tracking you
>> down for using a homemade and well designed filter or indeed any
>> piece of well designed equipment.
>
> In theory, you require BABT approved cable clips, the way the
> regulations
> are worded.
> And indeed I suspect the number of prosecutions for using equipment
> marked specifically as not to be connected to the BT network closely
> approaches 0.

But the charges raised by BT engineers significantly higher after they've
been called in to investigate why the line isn't working properly...

kraftee <kraftee@spamoff&die> wrote:
> Ian Stirling wrote:
>> Chip <(E-Mail Removed)> wrote:
>>> On Tue, 28 Jun 2005 19:25:43 +0100,it is alleged that "Joker7"
>>> <(E-Mail Removed)> spake thusly in uk.telecom.broadband:
>>>
>>> <snip>
>>>> I was of the understanding that your side of the wall is your and
>>>> not their network,ie no need for BT approval.
>>
>>> Technically anything connected to any phone jack that has access to
>>> an outside line in the UK is "directly or indirectly connected to a
>>> public telecommunications system" and therefore should have BABT
>>> approval (note, BABT= British Approvals Board for Telecommunications
>>> and is not part of BT). However, how good their enforcement is I
>>> don't know, I can't imagine them wasting the money in tracking you
>>> down for using a homemade and well designed filter or indeed any
>>> piece of well designed equipment.
>>
>> In theory, you require BABT approved cable clips, the way the
>> regulations
>> are worded.
>> And indeed I suspect the number of prosecutions for using equipment
>> marked specifically as not to be connected to the BT network closely
>> approaches 0.
>
> But the charges raised by BT engineers significantly higher after they've
> been called in to investigate why the line isn't working properly...

Which is why it'd be removed, before phoning them.