[nzlug] Line noise revisited

[Mathew Carley]

On Sunday 17 February 2008 10:43:40 cr wrote:

> the DSE PCMCIA modem in my laptop seems to be much less affected by it.
>   
I guess they figure you're going to be taking the DSE PCMCIA modem to 
some pretty dodgy places (by dodgy, I mean... to some log cabin in the 
mountains or something).
> Which leads me to the question, are some modems more tolerant of line noise 
> than others?  
I've found even internal laptop modems to be somewhat more resiliant to 
line noise... but then again this was years ago, so the same may not be 
true with the advent of cheaper laptops - I haven't used dialup in a 
very long time, except using my cellphone about a year ago (but even 
then, that wasn't really dialup)... or a few times in Thailand.
>  And, would putting some sort of high-cut filter in front of my 
> modem, possibly help?   I suppose one could be made up from chokes and 
> capacitors if I knew the design input impedance for modems; 
Maybe... even better if you can work out the frequency of the line noise 
so you can perhaps cancel it out (or maybe I'm wrong on how it works)...
> or maybe just a 
> ADSL line filter with the modem connected to the 'phone' side of it?
>   
I have a feeling ADSL line noise is completely different compared to 
regular, environmental, 
poorly-maintained-by-telecom-even-though-you-pay-a-line-maintenance-surcharge 
line noise. If you want to take the risk, you could get them to check 
for things like water on the line, though if they find nothing (quite 
often they cant, though in my opinion this is out of laziness) you're up 
for $80 (or maybe its more these days)...