Attenuation - at what frequency?

[Rik]

I note that, since I moved to WBC, my 2700 reports attenuation as 63db, rather than the 57db I 'enjoyed' under Max. However, on the diagnostics page, at 300kHz, it reports a 56db attenuation.

Does anyone know what frequency the higher figure is based on?

[Glenn]

Where in the chart does it show 63db?

[Rik]

It doesn't, it's in the summary page that figure is given, Glenn.

[Glenn]

everywhere I look says it at 300khz

[Rik]

http://192.168.1.254/xslt gives me the 63db figure, Glenn.

[Sebby]

I'm not sure tbh, Rik, but I know that ADSL2+ does cause reported attenuation to rise by a few dBs. I'm not sure what the technical reason(s) for this is, though.

[kinmel]

According to http://192.168.1.254/xslt?PAGE=C_5_3 for V6 firmware,  ADSLMax it is based on 300kHz too

[Steve]

Can you you force the 2wire to use adsl or adsl2 modality on a BT adsl2+ connection?

[Rik]

I'm not sure tbh, Rik, but I know that ADSL2+ does cause reported attenuation to rise by a few dBs. I'm not sure what the technical reason(s) for this is, though.

Support expect lower attenuation on ADSL2, Seb, which seems wrong to me given the higher frequencies in use.

[Rik]

According to http://192.168.1.254/xslt?PAGE=C_5_3 for V6 firmware,  ADSLMax it is based on 300kHz too

I'm on v5, so maybe that's the problem, Alan?

[Rik]

Can you you force the 2wire to use adsl or adsl2 modality on a BT adsl2+ connection?

No idea, Steve.

[Sebby]

Support expect lower attenuation on ADSL2, Seb, which seems wrong to me given the higher frequencies in use.

ADSL2 or ADSL2+? If you mean ADSL2+, support are definitely mistaken

[Sebby]

Can you you force the 2wire to use adsl or adsl2 modality on a BT adsl2+ connection?

I'm not sure about the 2Wire, but you can on the SpeedTouch.

[Rik]

ADSL2 or ADSL2+? If you mean ADSL2+, support are definitely mistaken

That's my feeling, Seb, and, afaik, WBC is ADSL2+.

[Sebby]

It is.

[Rik]

Mmm. Worrying...

[Steve]

I'm not sure about the 2Wire, but you can on the SpeedTouch.

Have we got a guinea pig?

[Rik]

 

I've got a bacon sandwich, does that count.

[Gary]

That's my feeling, Seb, and, afaik, WBC is ADSL2+.

On LLU ADSL2+ with Be/O2 attenuation went up, so I would agree here as I cannot imagine there is a massive difference in the base workings of adsl2+ even if its BT's implementation

[4Way]

AFAIK there isn't a tweak to get the 2700 to use ADSL2. I have done it done it with a Netgear DG834G V4 though.

[iankathy]

Hi All,

Could the attenuation be derived on a total power basis? The power delivered into a circuit by the exchange equipment is known, and maybe the DSP chip in the modem could derive the total received power. Just a thought.

Ian.

[Rik]

Could be, Ian, it's just odd, to me anyway, that it gives two different reports.

[MisterW]

My understanding is that the 2nd attenuation figure is the average, calculated across the ADSL frequency range. It is usually higher than the one at 300kHz since ADSL frequencies can go up to 1.1MHz ( on ADSL1/G.992.1) and attenuation is typically  greater at higher frequencies. On ADSL2+(G.992.5) the maximum frequency is 2.2MHz and so the average attenuation is therefore usually slightly higher since more high frequency tones are used.
ADSL2(G.992.3) is normally used where the line is not capable of handling the higher frequencies of ADSL2+, it uses the same frequency range of ADSL1 but somehow( presumably slightly different modulation) allows up to 12Mb speed rather than the 8Mb of ADSL1. Most often ADSL2 is used by negotiation between the router and DSLAM but some routers ( as indicated above ) have the option to force its use, but the 2700 has no such facility. Forcing its use can sometimes gives better results than ADSL2+ on long lines since it stops the attempted use of the higher tones where noise has more infuence and thus reduces the error counts.

[Rik]

Thanks for that.