On Sat 08 Jun at 18:47 Dave Hatch (3:711/808{at}fidonet) wrote to Arthur Marsh:

AM> As Frank Nitzsche has stated, V.22bis has a limit on the 
AM> maximum length of copper between the modems and the 
AM> hybrids (~5km maximum?). At my end, the length is 2355 
AM> metres.

 DH> I'm getting all disillusioned again.   I've been using 
 DH> one-shot 2400 baud calls to nearly everywhere on earth for 
 DH> the past few years, and always found it to be both reliable 
 DH> and fast to connect.  Method of choice for a single netmail 
 DH> message.   _Now_ he tells me it's busted...:-)

 DH> Details?   (I didn't see that thread.)

Look up the frequencies used by V.22bis - 1200 Hz and 2400 Hz.

Depending on whether you have loading coils on the lines or not, the 2400
Hz signal can drop below the noise floor with a not uncommon length of
access line - and V.22bis' adaptive equalisation can't do anything about
crumby S/N ratios.

 
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