techie question on SNR from dialup modem

zugvogel

Hi Lads,
I'm on a dial up connection with under ground cable back to the local exchange which is approx 3000 meters away. When I dialup for 90% of the time I usualy get 44kbits/sec connection speed 90% of the time. If I get less tha 40kbits/sec I usual disconnect and redial the iSP and will proably then get the 44 kbits/sec.
LAst night using the instructions below I tried to estimate the SNR for my phone line using the output from the modem in my laptop. ANyway I got an SNR of 53 which seems to be good I think. The carrier frequency was slightly less than 1959 Hz (approx 1850Hz I think) and I didn't see any output for symbol rate. Based on the SNR of 53 reported by the modem would you say I have a good line or does this measurement really have no meaning in the context of my line being suitable for DSL when my exchnage is enabled?

Instructions
In the Hyper Terminal white terminal screen, type AT and press the <Enter> key.
The letters OK appears.

NOTE: It is possible you may not see any letters appear on the screen as you type. If so, type ATE1 and press the <Enter> key.


Type the following command and press the <Enter> key after each command line.

AT&F&W
ATZ
ATX3DT, MY ISP number

The modem begins dialing.
Allow 30-45 seconds to pass, then press the plus <+> key on the keyboard numeric pad three times.
The letters OK appears.
Type AT#UG and press the <Enter> key.

The NO CARRIER message appears and indicates the call is disconnected. You may copy the contents to a text editor and print it, or scroll through the results on the screen and find the numeric value located to the right of the following entries:

Carrier Freq (Hz)
Symbol Rate
SNR (dB)

The carrier frequency should be 1959 Hz. A lower number indicates that not all the frequencies are available for data transmission.

The symbol rate is the actual baud rate of the modem. The fastest possible symbol rate is 3429. If the symbol rate is 3200 or lower, a V.90 connection may not be a possibility.

The SNR value, which is the signal-to-noise ratio, is the most important value for determining a stable V.90 connection. A perfect SNR would be 60dB, and a value above 50dB is rare. The value between 40dB and 50dB will support a stable V.90 connection. Any values between 35dB and 40dB will cause instability for a V.90 connection. An SNR below 35dB indicates that a V.90 connection is very unlikely.
To close the program, click the X in the top right hand corner of the program window.
The message You are currently connected. Are you sure you want to disconnect now? appears.
Click Yes.
The message Do you want to save session test? Appears.
Click NO to close it.

bealtine

zugvogel wrote: »

SNR of 53 which seems to be good I think.

An SNR of 53 is not just good it is excellent...based on this SNR
you should be able to get DSL on your line.

However your description seems to suggest noise or crosstalk on the line.

zugvogel

Hi Bealtine,
Thanks for the reply. I decided to run the test just out of interest and in the hope of learning something as well.
It looks like the cable serving me is good quality (fingers crossed). Have no idea when it was laid. It’s a bit weird really as I’m out in the sticks off a fairly small rural exchange and not the place you’d expect to find fibre backhaul and underground cables from the exchange to house (my house is two years old). I would guess that there are a fair few pair gains around here as well, and the over ground lines on the telephone poles are a joke. Some of the poles are at werid angles (boggy ground) with some of the lines within touching distance and in other places pulled pretty tight. I definitely wouldn’t like to be trying to get a DSL service on them!! And all within 35 miles of our capital city

Zug