@wyatt Bringing your own modem is indeed good advice for subscribers to a cable Internet provider that lets them do so. I had my own Arris SurfBoard during the last couple years that I was with Xfinity.
DOCSIS 3.1 signal drowns in noise 300 000 non-correctables in a minute.
The modem switches modulation like a windmill in a storm and occasionally drops 3.1. The end result being that the modem cable connection heats up to 47 °C which probably isn't helping at all.
Hardware I returned to Xfinity this afternoon. The Arris telephony modem was about 20 years old. The cable box / DVT was not much younger.
We dropped cable TV, VOIP, and stopped renting modems (bought my own Arris S33v3) very recently, saving hundreds of dollars per month on the bill.
#Xfinity #cable #cabletv #vintage #networking #vintagehardware #docsis #telephony #modem #modems
(8/n)
SUMMARY OF XFINITY'S DOWNSTREAM CHANNEL LAYOUT IN MY AREA
Low band edge: 108MHz. This makes sense - the whole reason I bought this modem over my previous modem, is that the Hitron CODA is the cheapest of the few that Xfinity will provision for more upstream channels (faster upload speeds), which pushes the start of the downstream channels higher
High band edge: 1002MHz
Total span: 894MHz
Total QAM allotment: 540MHz (60.4%) in 90 channels (6MHz each)
Total OFDM allotment: 336MHz (37.6%) in 3 channels (48MHz, 96MHz, 192MHz)
Total unused: 18MHz (2.0%) in 3x 6MHz gaps
108MHz-246MHz: 23x 6MHz QAM channels
246MHz-252MHz: 1x 6MHz unused
252MHz-354MHz: 17x 6MHz QAM channels
354MHz-360MHz: 1x 6MHz unused
360MHz-648MHz: 48x 6MHz QAM channels
648MHz-744MHz: 1x 96MHz OFDM channel
744MHz-756MHz: 2x 6MHz QAM channels
756MHz-762MHz: 1x 6MHz unused
762MHz-810MHz: 1x 48MHz OFDM channel
810MHz-1002MHz: 1x 192MHz OFDM channel
(6/n)
And we get a nice little UI as a result!:
1. A spectrum analyzer with configurable center frequency/bandwidth span
2. Per-downstream-channel plots of Power (in dBmV - remember characteristic impedance is 75Ω here) and Modulation Error Ratio (in dB) over time
3. Constellation diagrams of any of the active downstream QAM channels!
These are pretty cool - someone has done some good work in developing this feature. Lots of companies simply got rid of the spectrum analyzer functionality in their modems instead of fixing the bug after the Cable Haunt (https://github.com/Lyrebirds/Cable-Haunt-Report/releases/latest/download/report.pdf) vulnerability came out a few years ago, which is a shame since it's such a great learning and debugging tool. So I'm happy to see Hitron is actually working on adding this functionality to a modem that didn't have it yet.
#electronics #docsis #cablemodem
(5/n)
The "Spectrum" hidden tab is a little more complicated - the javascript isn't just grabbing some data from a .asp page and displaying it in a table, it's a whole application with buttons and fancy graphs. So I figured out a devtools javascript console incantation to get the main page to load it, ignoring the fact that it's marked as not visible:
```js
$('#maincontent').html('');
var loadPage = "advanced_spectrum.html"
$('#maincontent').load(loadPage, function(response,status){
if (status=="success") {
$("a").unbind("click");
}
});
$('#maincontent').fadeIn();
```
(This is basically ripped from /js/mainApp.js, lines 305-321)
#electronics #docsis #cablemodem
Damian Yerrick
Matti Järvinen
Blake Patterson
kwest_tech