Line Loss and S/N ratio.

Line Loss and Signal/Noise ratio both measured in dB.

Q1. From where or how can I find the characteristcs of my particular
phone line?

Q2. Since line loss increases with frequency, at what frequency is
the dB line loss specified?

Q3. Alternatively, how many dB loss per mile is a typical local
line, and at what frequency?
----
Reg.




Reg Edwards

On Wed, 26 Oct 2005 18:58:13 +0000 (UTC), "Reg Edwards"
<(E-Mail Removed)> wrote:

>Line Loss and Signal/Noise ratio both measured in dB.
>
>Q1. From where or how can I find the characteristcs of my particular
>phone line?
>

Unless you already have ADSL, you can't until you order it, when if
you have a long line, BT will test it (and may even tell you what the
result is, if you ask nicely).

>Q2. Since line loss increases with frequency, at what frequency is
>the dB line loss specified?
>

The one that ADSL uses. I don't actually know what frequency that is,
but it is the only measurement they ever use when talking about ADSL
suitability, so they never state the frequency it is measured at.

>Q3. Alternatively, how many dB loss per mile is a typical local
>line, and at what frequency?

Typically, about 10dB per Km, but it does vary considerably.
--
Alex Heney, Global Villager
Murphy's law needs to be repealed.
To reply by email, my address is alexATheneyDOTplusDOTcom

Reg Edwards wrote:
> Line Loss and Signal/Noise ratio both measured in dB.
>
> Q1. From where or how can I find the characteristcs of my particular
> phone line?

Tricky, but once you have ADSL enabled some routers/modems have firmware
that allows a display of attenuation vs frequency (actually bin number,
so multiply that by 4000 to get frequency). Draytek 2600 does this for
instance.

>
> Q2. Since line loss increases with frequency, at what frequency is
> the dB line loss specified?

I'm not sure there is a standard, but usually at 300kHz or so.

>
> Q3. Alternatively, how many dB loss per mile is a typical local
> line, and at what frequency?

Nominally 10dB/km, but often a little more or less, again measured at
300kHz. For example, my line is approximately 3.85km long, the loop
attenuation displayed by my router is 43.5dB (on the status page, so at
a spot frequency, see above).

--

Brian Morrison

please observe reply-to address

"Brian Morrison" wrote -

> > Q3. Alternatively, how many dB loss per mile is a typical local
> > line, and at what frequency?
>
> Nominally 10dB/km, but often a little more or less, again measured
at
> 300kHz. For example, my line is approximately 3.85km long, the loop
> attenuation displayed by my router is 43.5dB (on the status page, so
at
> a spot frequency, see above).
====================================

Thanks very much Brian.

I can tell you are an expert from your correct use of " kHz ". ;o)
----
Reg.