I am using a Motorola SB6121 modem, I have Performance Internet Service. There is one 0-1000 MHz splitter between my modem and the point where the Comcast's RG-6 cable penetrates the wall of my home. About 200 feet of RG-6 cable runs from my home to the tap point on the pole directly in front of my home.
I have had fairly good intenet service until a few weeks ago, with the Comcast Speedtest page typically showing download speeds of 2 to 5 mbps and upload speed of 5 mbps. Occasionally (but not often) my download speed has increased to 10 to 20 mbps.
For several weeks, but only during daylight hours, my internet service has had an unreliable connection and less than 1 mbps download speed. For the last few days I have been unable to connect to the internet during the middle of the day. My HDTV service appears to be normal during all periods of unreliable internet service. Internet service always returns to normal late in the afternoon and all night.
I called 1-800-COMCAST last week to report this problem, they said that the next required step is a technician visit to my home which scheduled for today but was cancelled because of weather. Hopefully my internet connection problem will be present during the visit.
I tried to improve my internet service during the day by connecting Comcast's RG-6 cable that enters my home directly to my modem (my modem is less than 24 inches from the outside wall penetration point) and bypassing my splitter. Internet performance improved only slightly and often I could not connect to the internet during the day. During normal internet service at night my splitter does not degrade internet service at all. I've begun to make records of my modem signal levels when performance is normal at night and when my internet connection is unreliable during daylight hours.
During normal internet service early this morning, I have four bonded QAM256 downstream channels with 4 dBmv power levels and 36-37 dB signal to noise ratios. Upstream power level is 50 dBmv and there are four bonded 64QAM upstream channels. Comcast Speedtest shows 10 mbps upload speed and 5 mbps download speed. The last entry in my modem log is at 16:18:50 yesterday (Sunday). The number of uncorrectable codewords shown on the signal page has not changed in more than 12 hours and the number of correctable codewords has increased by less than ten codewords on each pf the four channels.
Yesterday (Sunday) my internet service was very unreliable during most of the dayllght hours, with very frequent modem reboots and complete loss of internet connection. Internet service suddenly returned to normal after 4:20 p.m. (the last entry in my modem log is 16:18:50). Upstream power was 57 dBmv during the day and remained at 57 dBmv until well into the night, and was down to 51 dBmv after midnight.
The log shows frequent MDD timeouts. MDD recoveries after MDD loss, partial service fallbacks until the last log entry at 16:18:50 During the period of unreliable service, one of the four downstream channels had 27 dBmv SNR but the other three channels had 36 dB SNR. During much of the day only three downstream channels were bonded and the low SNR channel (561 MHz) was no longer shown on the signal page. During unreliable internet service, only one upstream channel was shown on the signal page with 57 dBmv power level and 16QAM modulation.
My internet connection completely failed for more than one hour on Saturday afternoon and was unreliable during most daylight hours. On Saturday afternoon there were three bonded downstream channels with 36, 36 and 32 SNRs and one upstream channel with 57 dBmv power level and 16QAM modulation, with ranging status on the signal page frequently showing :T4 TimeOut. The log page was updating several times per minute with lost MDD timeouts, MDD recoveries, Partial Service Fallbacks and modem reboots. Service suddenly returned to normal late in the afternoon, although upstream signal level was 57 dBmv until late at night.
I will continue to make printed copies of the modem signal page and log page until the technician visits.
Thanks for any feedback.
W3LPL