Question about downstream power output

I have recently aquired a D-Link DSL-2740B router which although is working
OK there are a couple of issues I'm trying to sort out. The main one right
now is that it always reports the downtream power output as 0.0dBm both on
its stats web page and on the output of the adsl command when I telnet into
the router. The upstream power is usually shown as about 12.9dBm.

Now my question is on an ADSL2+ connection should I see a valid non-zero
value in this field? Do others see this as a non-zero value on this router?

If it should show a non-zero value does this indicate a problem with this
router?

Thanks

Stuart Rogers wrote:

> I have recently aquired a D-Link DSL-2740B router which although is
> working OK there are a couple of issues I'm trying to sort out. The main
> one right now is that it always reports the downtream power output as
> 0.0dBm

> If it should show a non-zero value does this indicate a problem with this
> router?

I believe that the downstream power output isn't calculated by your router,
the value is communicated to the router by the kit in the exchange. So if
there is a minor incompatibility between the DSLAM and your router, you'll
see nothing or nonsense in that field. Alternatively, it may be a bug in
the router's firmware.

--
<http://ale.cx/> (AIM:troffasky) ((E-Mail Removed))
21:09:29 up 17 days, 2:00, 2 users, load average: 0.05, 0.06, 0.01
They call me titless because I have no tits

alexd <(E-Mail Removed)> wrote in news:(E-Mail Removed):

> Stuart Rogers wrote:
>
>> I have recently aquired a D-Link DSL-2740B router which although is
>> working OK there are a couple of issues I'm trying to sort out. The
>> main one right now is that it always reports the downtream power
>> output as 0.0dBm
>
>> If it should show a non-zero value does this indicate a problem with
>> this router?
>
> I believe that the downstream power output isn't calculated by your
> router, the value is communicated to the router by the kit in the
> exchange. So if there is a minor incompatibility between the DSLAM and
> your router, you'll see nothing or nonsense in that field.
> Alternatively, it may be a bug in the router's firmware.
>

Well I've now tested another router of a different make on the same
connection and it does not display this value either. I guess both may be
not communicating with the DSLAM properly over this. I suppose it could be
that the DSLAM may not be sending the data either.

Stuart Rogers wrote:
> alexd <(E-Mail Removed)> wrote in news:(E-Mail Removed):
>
>> Stuart Rogers wrote:
>>
>>> I have recently aquired a D-Link DSL-2740B router which although is
>>> working OK there are a couple of issues I'm trying to sort out. The
>>> main one right now is that it always reports the downtream power
>>> output as 0.0dBm
>>> If it should show a non-zero value does this indicate a problem with
>>> this router?
>> I believe that the downstream power output isn't calculated by your
>> router, the value is communicated to the router by the kit in the
>> exchange. So if there is a minor incompatibility between the DSLAM and
>> your router, you'll see nothing or nonsense in that field.
>> Alternatively, it may be a bug in the router's firmware.
>>
>
> Well I've now tested another router of a different make on the same
> connection and it does not display this value either. I guess both may be
> not communicating with the DSLAM properly over this. I suppose it could be
> that the DSLAM may not be sending the data either.

Well perhaps your exchange IS transmitting at 0dbM.


Its a perfectly reasonable power level.

The Natural Philosopher <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> Stuart Rogers wrote:
>> alexd <(E-Mail Removed)> wrote in
>> news:(E-Mail Removed):
>>
>>> Stuart Rogers wrote:
>>>
>>>> I have recently aquired a D-Link DSL-2740B router which although is
>>>> working OK there are a couple of issues I'm trying to sort out. The
>>>> main one right now is that it always reports the downtream power
>>>> output as 0.0dBm
>>>> If it should show a non-zero value does this indicate a problem
>>>> with this router?
>>> I believe that the downstream power output isn't calculated by your
>>> router, the value is communicated to the router by the kit in the
>>> exchange. So if there is a minor incompatibility between the DSLAM
>>> and your router, you'll see nothing or nonsense in that field.
>>> Alternatively, it may be a bug in the router's firmware.
>>>
>>
>> Well I've now tested another router of a different make on the same
>> connection and it does not display this value either. I guess both
>> may be not communicating with the DSLAM properly over this. I suppose
>> it could be that the DSLAM may not be sending the data either.
>
> Well perhaps your exchange IS transmitting at 0dbM.
>
>
> Its a perfectly reasonable power level.
>

Yes it could be but I'm on a 3km line and so I would have thought it
would need some power!

"Stuart Rogers" <(E-Mail Removed)> wrote in message
news:Xns9B4BD21714F64stuartbroadstairsorg@130.133. 1.4...
> The Natural Philosopher <(E-Mail Removed)> wrote in
> news:(E-Mail Removed):
>
>> Stuart Rogers wrote:
>>> alexd <(E-Mail Removed)> wrote in
>>> news:(E-Mail Removed):
>>>
>>>> Stuart Rogers wrote:
>>>>
>>>>> I have recently aquired a D-Link DSL-2740B router which although is
>>>>> working OK there are a couple of issues I'm trying to sort out. The
>>>>> main one right now is that it always reports the downtream power
>>>>> output as 0.0dBm
>>>>> If it should show a non-zero value does this indicate a problem
>>>>> with this router?
>>>> I believe that the downstream power output isn't calculated by your
>>>> router, the value is communicated to the router by the kit in the
>>>> exchange. So if there is a minor incompatibility between the DSLAM
>>>> and your router, you'll see nothing or nonsense in that field.
>>>> Alternatively, it may be a bug in the router's firmware.
>>>>
>>>
>>> Well I've now tested another router of a different make on the same
>>> connection and it does not display this value either. I guess both
>>> may be not communicating with the DSLAM properly over this. I suppose
>>> it could be that the DSLAM may not be sending the data either.
>>
>> Well perhaps your exchange IS transmitting at 0dbM.
>>
>>
>> Its a perfectly reasonable power level.
>>
>
> Yes it could be but I'm on a 3km line and so I would have thought it
> would need some power!

Googled for dBm and found:

"Stuart Rogers" <(E-Mail Removed)> wrote in message
news:Xns9B4BD21714F64stuartbroadstairsorg@130.133. 1.4...
> The Natural Philosopher <(E-Mail Removed)> wrote in
> news:(E-Mail Removed):
>
>> Stuart Rogers wrote:
>>> alexd <(E-Mail Removed)> wrote in
>>> news:(E-Mail Removed):
>>>
>>>> Stuart Rogers wrote:
>>>>
>>>>> I have recently aquired a D-Link DSL-2740B router which although is
>>>>> working OK there are a couple of issues I'm trying to sort out. The
>>>>> main one right now is that it always reports the downtream power
>>>>> output as 0.0dBm
>>>>> If it should show a non-zero value does this indicate a problem
>>>>> with this router?
>>>> I believe that the downstream power output isn't calculated by your
>>>> router, the value is communicated to the router by the kit in the
>>>> exchange. So if there is a minor incompatibility between the DSLAM
>>>> and your router, you'll see nothing or nonsense in that field.
>>>> Alternatively, it may be a bug in the router's firmware.
>>>>
>>>
>>> Well I've now tested another router of a different make on the same
>>> connection and it does not display this value either. I guess both
>>> may be not communicating with the DSLAM properly over this. I suppose
>>> it could be that the DSLAM may not be sending the data either.
>>
>> Well perhaps your exchange IS transmitting at 0dbM.
>>
>>
>> Its a perfectly reasonable power level.
>>
>
> Yes it could be but I'm on a 3km line and so I would have thought it
> would need some power!

I googled and found :
http://www.jneuhaus.com/volts_to_dBm.html

which shows the line:

Volts-rms 0.775 Vrms
Volts-peak-to-peak 2.191 Vpp
dBm(Z=50ohm) 10.8 dBm
dBm(Z=75ohm) 9.0 dBm
dBmv(Z=75ohm) 57.8 dBmv
dBm(Z=600ohm) 0.0 dBm

So 0.0 dBm is 0.775 Vrms across 600 ohm i.e. 1mW - or a perfectly adequate
level of power to get down 3km of phone line.

A mate at BBC broadcasting house used to joke that their output was 1mW into
600 ohm for each programme channel - an expensive way to sell electricity!!!

--
Graham J

Stuart Rogers wrote:
> The Natural Philosopher <(E-Mail Removed)> wrote in
> news:(E-Mail Removed):
>
>> Stuart Rogers wrote:
>>> alexd <(E-Mail Removed)> wrote in
>>> news:(E-Mail Removed):
>>>
>>>> Stuart Rogers wrote:
>>>>
>>>>> I have recently aquired a D-Link DSL-2740B router which although is
>>>>> working OK there are a couple of issues I'm trying to sort out. The
>>>>> main one right now is that it always reports the downtream power
>>>>> output as 0.0dBm
>>>>> If it should show a non-zero value does this indicate a problem
>>>>> with this router?
>>>> I believe that the downstream power output isn't calculated by your
>>>> router, the value is communicated to the router by the kit in the
>>>> exchange. So if there is a minor incompatibility between the DSLAM
>>>> and your router, you'll see nothing or nonsense in that field.
>>>> Alternatively, it may be a bug in the router's firmware.
>>>>
>>> Well I've now tested another router of a different make on the same
>>> connection and it does not display this value either. I guess both
>>> may be not communicating with the DSLAM properly over this. I suppose
>>> it could be that the DSLAM may not be sending the data either.
>> Well perhaps your exchange IS transmitting at 0dbM.
>>
>>
>> Its a perfectly reasonable power level.
>>
>
> Yes it could be but I'm on a 3km line and so I would have thought it
> would need some power!

No, the power level at the exchange is pretty constant I think. That's
why the long line loses bandwidth..increase the power and it will start
buggering other peoples DSL..