[plug] wanted: 56k modem

[Kai Jones]

Apologies for replying to my own post, but even though modems have 8kHz
sampling they're also not good at handling even relatively strong line
noise.

Classic example is if you live anywhere near the 720kHz 6WF ABC
transmitter at Hamersley, if my information is correct it pumps out
20kW, anyone within cooee of that transmitter either needs to use a
Woomera or other modem with eight line transformers inside it to help
smooth any effects of eletrical change, mostly impedence, that may come
down the line with changes in weather and other variables, and cause
disconnection.

I used to live in Balga, the signal from that transmitter was so strong
I could hear on the phone when I went to make a call, dial-up
connections were hopeless without at least two filters.

When I was working for WestNet a few years ago, I called one guy in
Hamersley who lived about as close as you can get to that transmitter,
he had two choices - slow his modem down to like 14,400 and have a more
stable connection, or leave it connecting at 56 and drop every other
minute.

End of the day, modems don't like line noise, as long as there's a
signal on your line which is louder/stronger than the signal between
your modem and the one at the other end, it'll drop.

-----Original Message-----
From: plug-bounces at plug.org.au [mailto:plug-bounces at plug.org.au] On
Behalf Of Kai Jones
Sent: Wednesday, 14 June 2006 11:59 AM
To: plug at plug.org.au
Subject: RE: [plug] wanted: 56k modem

Go for your life, if you want to make a small loop as close as possible
to your modem and another as close as possible to your wall socket that
will also help...having a loop in the middle will have very little
effect since either side of the loop your phone line acts as an antenna
for RFI and negate the purpose of the loop (filter). If you want, maybe
try an ADSL filter on that line, even if you don't have ADSL there are
usually two small wound toroids in that plastic box which might help.

Michael, in regard to your comments about PC's not handling the load,
from my understanding it's not about load but that external modems are
built for one purpose and internal's don't have the same in-built
dedicated functionality therefor don't usually perform as well.

I'm happy to be corrected if anyone has more accurate info.

-----Original Message-----
From: plug-bounces at plug.org.au [mailto:plug-bounces at plug.org.au] On
Behalf Of Jason Posavec
Sent: Wednesday, 14 June 2006 11:17 AM
To: plug at plug.org.au
Subject: Re: [plug] wanted: 56k modem

That does explain why my tv manual had me wrap the speaker wires around
metal plugs!

Will of course now be conducting experiments to see if looping my phone
cable has any affect on my connection speeds :D

Jason



Kai Jones wrote:
> Noise := electronic noise.
>
> Any wire wound into a coil is effectively a transformer with an air
core
> (instead of having an iron core as you see in most transformers), the 
> transformers core will modify inductance/capacitance/resistance of the

> loop, depending on the size of the loop and how many loops it should
act
> like a filter for electronic noise which is in the frequency range for

> whatever size you've made your loop.
>
> Looping around ferret bead(s) as well as using normal air core loops, 
> can also have a good effect on supressing electronic noise.
> Make sense ?
_______________________________________________
PLUG discussion list: plug at plug.org.au
http://www.plug.org.au/mailman/listinfo/plug
Committee e-mail: committee at plug.linux.org.au