Here in Ames, Iowa, I have been experiencing a very frustrating intermittent signal problem that is affecting all service coming through the wire from Mediacom into my apartment.
I first began to notice this about July 26, 2013. At various times during any particular day, but usually evenings or early mornings, the downstream signal level will flicker between two ranges. The upper range is -3 to -5 dBmV with SNR of around 36, and this gives good signal on the low analog channels here in town. The lower range is -17 to -21 dBmV with a SNR of 29 or below, and this gives a somewhat snowy picture on most of the low analog chanels, and on the low analog channels which carry the OTA broadcast channels 5, 8, 11, and 13 the picture is almost completely destroyed with something that looks like ingress interference.
The effects on the analog channels coming through the wire, however, are only part of the story. My digital-ready clearQAM LCD tv is able to able to make a decent picture and sound from either signal level range, but when the signal strength flickers between the two, the picture severely pixelates or blacks out completely and the sound loses sync or blacks out with the picture. The Arris model cable modem I rent from Mediacom has tried to do a better job of not losing sync or having T3 or T4 timeouts, well, better than the Thompson 425 model that the Arris replaced back in May of this year. Nevertheless, when the downstream signal is so low and then flickers the cable modem loses packets or re-syncs itself. This degrades the downstream bandwidth I get from normal of 10+ Mbps down to less than 2 Mbps. It also tends to hang and freeze the VPN and long-running TCP (RDP and SSH) sessions I must use when I'm called for after-hours work.
As I looked around the apartment complex a few weeks ago I took notice of a damaged coax cable running around the outside of the building from the Mediacom distribution box which takes the feed from the pole around to the locked closet where the filter blocks reside. That cable run had multiple damaged sections with cuts and cracks through the jacket and the woven shield right down to the core conductor. The damage to this cable run was exacerbated by recent work the property owner had done to replace some outside stairs which stretched the cable. I put in a call to Mediacom on August 2, and the tech they sent out on August 7 replaced the cable. Unfortunately, the intermittent signal problem I described above returned not even four hours after the tech left.
Also, I've tried loosening and re-tightening every connector I can find from the wall plate inward, and I've tried bypassing any and all splitters with no effect. Right now it's just the Mediacom-installed 1-in,2-out splitter for the cable modem and then straight on to the TV. Even so, the downstream signal levels and their flickering is affecting both the TV and the cable modem. Therefore, it would seem the signal problem originates somewhere upstream of the wall plate.
Curiously, even when the downstream signal levels drop from the -3/4/5 range to the -17/-21 range and flicker between them, the upstream signal levels reported by the cable modem remain fairly steady at between 49 and 51 dBmV.
I said before I live in an apartment, but I know for a fact the remaining coax between the pole feed and my apartment has been in-wall for 20+ years. By the way, there are also some tree branches through which the feed from the pole is fed (or that have grown out around it).
From what I've researched, I think there are the following remaining possible causes for this loss of downstream signal and the flickering that is giving the TV's digital tuner and the cable modem so many problems.
1. Damaged outside feed cable from line distribution box to filter blocks.
Since this problem is continuing after the cable was replaced, I tend to discount this cause.
2. Physical stress on the line cable from the pole to the outside distribution box.
Since there has been quite a lot of wind pushing around the tree branches, and even under heavy winds this signal loss and flickering has not manifested, I tend to discount this cause. Also, why no matching significant upstream signal loss?
3. Aging in-wall cables or splitters that were damaged or finally gave out.
Other Mediacom field techs have commented about the age of this wiring, but if this were the case I would expect more consistent signal problems rather than them manifesting in clusters around evening sunsets or morning sunrises. Also, why no matching significant upstream signal loss?
4. Another tenant connected a piece of equipment to their wall plate that is throwing out interference.
This is, of course, possible, but in all the years I've lived here I have not yet encountered it. Also, why no matching significant upstream signal loss?
5. A loose connection in the locked filter block room.
I cannot check this myself, and will take a field tech with the key from the property owner. Still, why no matching significant upstream signal loss?
6. A loose or damaged Mediacom line cable somewhere on the distribution path to the building.
This is, of course, possible, but in all the years I've lived here I have not yet encountered it. Also, why no matching significant upstream signal loss?
7. A malfunctioning Mediacom line/distribution amp somewhere upstream.
I'm afraid this seems to be the remaining explanation that seems to best fit the observed facts.
As I said, I have observed this problem going on for almost three weeks, and as I said it is intermittent. Given that when this problem manifests it significantly degrades the data connectivity I pay for and ruins the picture and sound for all digital and analog channels, to call this problem frustrating is very much an understatement.
I have been documenting when this problem manifests to try to correlate occurrences, and if necessary I'll be speaking to the other tenants to see if one of them is responsible. However, given the fact about negligible changes to upstream cable modem signal strength when the downstream signal loss/flicker manifests, I suspect it will be necessary for Mediacom to troubleshoot their distribution equipment and line cabling feeding this building. Either that or I'll need to have a Mediacom field tech on-call to troubleshoot the problem when it intermittently manifests.
Does anyone else have any other ideas?
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