cliveb
01-07-2004, 09:35
Over the last week, my 600k service has been intermittent. I'm using a SACM (Ambit 120), and its RDY and SYNC lights always remain solid: no blinking to indicate any problems. A CM reboot seems to bring thing back to life.
However, I've been monitoring the CM diagnostics, and here's what typically happens. After a reboot, the upstream transmit power will start out around 52-55dBmV and, although this seems a little high, everything runs fine. Then, over the course of anywhere between half an hour and several hours, it gradually drops down to somewhere between 37 and 42dBmV. At this point, the T3 timer expiry counter starts going up and net access gets unreliable. There have been a couple of occasions when my router has then failed to renew its DHCP lease.
From my (very limited) understanding of how the CM works, I think that the upstream power level is determined at boot-up so that the signal level sent is sufficiently high to overcome any noise on the cable. Therefore one would expect that if it needs to be 50+ to start with, then when it reduces one can expect the signal to be lost in noise. So that seems to fit the symptoms. What I don't know is if the CM continually monitors the required upstream transmit power and will adjust itself downwards if appropriate.
On Robin Walker's excellent site, it states "rapidly fluctuating power levels might be a sign of a failing amplifier in the ISP's network, or a bad cable connection, and should normally be investigated". My power levels aren't fluctuating rapidly, they're gradually decreasing. Is this normal?
However, I've been monitoring the CM diagnostics, and here's what typically happens. After a reboot, the upstream transmit power will start out around 52-55dBmV and, although this seems a little high, everything runs fine. Then, over the course of anywhere between half an hour and several hours, it gradually drops down to somewhere between 37 and 42dBmV. At this point, the T3 timer expiry counter starts going up and net access gets unreliable. There have been a couple of occasions when my router has then failed to renew its DHCP lease.
From my (very limited) understanding of how the CM works, I think that the upstream power level is determined at boot-up so that the signal level sent is sufficiently high to overcome any noise on the cable. Therefore one would expect that if it needs to be 50+ to start with, then when it reduces one can expect the signal to be lost in noise. So that seems to fit the symptoms. What I don't know is if the CM continually monitors the required upstream transmit power and will adjust itself downwards if appropriate.
On Robin Walker's excellent site, it states "rapidly fluctuating power levels might be a sign of a failing amplifier in the ISP's network, or a bad cable connection, and should normally be investigated". My power levels aren't fluctuating rapidly, they're gradually decreasing. Is this normal?