[Tfug] modem and router combo

[Ronald Sutherland]

On 10/27/07, christopher floess <skeptikos at gmail.com> wrote:
>
> > Christopher is there any chance your cable modem is getting hot
>
> Actually that seems like it MIGHT be an issue. I noticed the
> other day that I was dl'ing at an unprecidented speed. I
> actually have their low level service (I think it's supposed
> to top out at 256k), but I was way faster than that. But I
> wonder how fast you have  to be for heat to start becoming
> an issue b/c my modem is in a very well ventilated place.
>
>
Downloading should not work the RF amplifier much (only sending), so little
heat from that...
It all has to do with how much current the amplifier has to push into the
cable to change the potential.
Adding impedance reduces the amount of current to get to a desired potential
(voltage level), although after the impedance the level is even lower. Every
data bit that goes out of the modem is a finite amount of current from the
RF amplifier, and that current heats the amplifier. The amplifier is tied to
a thermal sink, a reservoir for heat that also spreads the heat out and
moves it to ambient (where your ventilation helps). The rate that heat moves
to ambient is often less than the rate heat is added by the amplifier at
high transmit rates so heat builds up until a thermal sensor trips that
shuts down the amplifier (indeed a good calculus problem).

I hope the cable installer person can find the problem, since they need to
set the system up so it does not go into thermal shutdown. I'm starting to
think that adding impedance may be a common fix. Also as connections are
made to the cable its reactance will change so the amount of heat will
change. The good news is that every house gets a splitter signal which
limits the effects of one user on another, for example if some next door is
shorting the cable TV to keep the kids out of the house.

256k sounds like low DSL? Throttled data rates are done by buffering data or
resending data packets, both cost them extra, everyone should request the
low speed >:-)