Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[NewtronStar]

Hello Guys & Girls and happy Easter 

I would like to understand how the Power dBm / dBmV works on BroadBand and as it's shown on most monitering programs it must be very important

All I know at the moment from research is it's decibels and millivolts (power ratio) and SNR seem to be part of this equation.

So lets give you my Power dBmV > 11.1 Downstream and 0.6 Upstream, and please could you put this in laymans terms 

Cheers 

[kitz]

I wrote a little bit about it here.   

It is important, because the more power supplied, then the higher your SNR(m) will be, thus a higher sync speed.    Our routers have the ability to up the power slightly if its struggling after say bitswap or errors.  On adsl2+ its not uncommon to see 18dB upon sync but after time it may ramp up to 20dB.

However.....  it should be bourne in mind that PSD masks play a huge part in this process too and will cut back power on shorter lines.   The PSD masks are much an undisclosed feature..  all I know is there are supposed to be 5 different profiles depending upon line length (for adsl/adsl2+), but I dont know any actual parameters or what tones are masked.  At one time I searched to find out more information but drew complete blanks on this subject.

When it comes to VDSL  the PSD masks are different again.. and further complicated by multiple sub-channels, each having what appear to be their own parameters.

[roseway]

The units for measuring power are dBmW (normally just referred to as dBm), not dBmV. I wrote a short explanation here: http://wiki.kitz.co.uk/index.php/Decibels#Decibels_used_as_power_measurement

[burakkucat]

N*Star -- You might like to take a look at the last few posts to this thread, where 4c and b*cat were wittering on about this & that and the relationship between power (expressed as dBmW) & voltage (expressed as mV) of an audio circuit.

[NewtronStar]

Many thanks Kitz and Eric & my big Black cat BC for responding back, I am finding it hard to get my head around dBm and I am reading both your links it may take a few nights for it to sink into the grey matter, it's something I look at in the stats but don't really understand what it meens and how to interpret those figures from one line to another 

[burakkucat]

Hesitantly, I offer a link to a Wikipedia page on dBmW . . .

That page provides links to other related topics and, as a result of following them, etc, etc, one will eventually end up reading about stendec. 

(As with any foray into Wikipedia, the result is a rapid deviation which ultimately homes into Mornington Crescent.    )

[NewtronStar]

Hesitantly, I offer a link to a Wikipedia page on dBmW . . .

That page provides links to other related topics and, as a result of following them, etc, etc, one will eventually end up reading about stendec. 

I have to say BC thats was a good read