[TriLUG] OT: PAM / QAM (was: Home Depot CAT-5)

[Rob Lockhart]

Jim Ray wrote:

> >> 1000BaseT does use all 4 pairs.
> >>
> > Yeah, that as well as that freaky PAM-5 signaling. Has anyone else
> > read the standard for PAM-5? It's a neat idea.
> >
>  [JR>] pam is definitely a no brainer. Aerosol can, spray it in
>  frying pan, done. No problem. Works for getting a bunch of cables
>  through conduit as well.
>

Just be sure to not get that "PAM" on your hands as you climb down a 
ladder or your feet walking around your attic.  :-)

PAM (Pulse Amplitude Modulation) is pretty crude signalling that has 
been used for years, at least as far back as ISDN and certainly before 
then.  If you've ever seen what is involved in ADSL or VDSL (QAM), 
you're really impressed at the level of DSP horsepower required, 
especially on the frequency overlapping technologies.  Ironically, some 
of these complicated algorithms are done with Turbo codes and huge 
constellations for things like v.90.  Cable modem ASIC guys have a far 
easier job (complexity).