NETGEAR is aware of a growing number of phone and online scams. To learn how to stay safe click here.
Forum Discussion
Solved
Problems with CM1150V upstream on Comcast Xfinity
There are a number of past threads (now closed, or I'd be replying to them) about problems people have had with the upstream path on a CM1150V with Comcast Xfinity. I believe I understand the underl...
sleat wrote:So it makes sense that the BGA3131 is designed to operate up to 205MHz. However, notice the sentences I've highlighted. In my case, Comcast is running four upstream QAM channels (no upstream OFDM) at frequencies of 173MHz, 273MHz, 303MHz, and 367MHz. So not only are they asking the CM1150V do do something it was never designed to do, they are blatantly violating the DOCSIS 3.1 spec!
sleat I've read this thread multiple times (having my own Upstream Issues!) and took this at face value;
but only just spotted this fundamental error in your analysis ..........
The Comcast Upstream frequencies are not as you indicate, you are a factor of 10 off
i.e. they are 17.3MHz, 27.3MHz, 30.3MHz and 16.7MHz
i.e. 17300000 Hz (5 zeros) = 17,300,000Hz or 17.3MHz
So actually operating well within the DOCSIS 3.1 Spec and well within the design capability of the Chipset.
As I've said I'm having my own Upstream Issues with my CM1150V (and actually got a replacement from Netgear) and there is definitely a problem - but it's not because it's being asked to operate outside its spec.
The modem fails when the BCM3131 upstream amplifier gets too cold, which is somewhere between 50F and 60F. You can dig through the whole saga in the past posts if you want to know more, just ignore the whole aspect where I went down the rabbit hole regarding Comcast upstream frequencies. That was just a complicated distraction resulting from a simple mistake.
Interesting. Didn't know that cold temp would be a cause of that failure.
Is the modem in a room that is always cold? I suppose one work around would be to have a heater on it if you need this modem to be in a cold room. Kind of a corner case issue here though. Most rooms on average are 65-70F I would guess and the modem running normally would be warmer then that internally. Usually the modems run fairly warm on there own so shouldn't be a cooling issue. Very interesting though.