Re: Plasma TV Causing Cable Modem Dropouts

Wish you had posted numbers earlier. While the 50dBmV transmit is fine, the -15dBmV on the downstream is not. Neither is the SNR of 29dB.

After reconfiguring your splitter arrangement, you can't complain a bit about your levels that you have now -- especially that SNR of 36dB.

You do have a valid concern about the signal level Comcast is providing you. The minimum allowed by the FCC is 3dBmV at the groundblock. If your system is 256QAM, doing the math puts your signal level at ~3dBmV. If it is 64QAM, your signal level is ~7dBmV.


CIAO!

Ed N.

manowak via HWKB.com wrote:
That's basically what I've concluded. Here's my working hypothesis of the
problem: there's been a decline in the signal quality I've been getting from
Comcast. Two months back, that decline was enough to cause my old modem to
drop out with interference from the TV. The newer modem was
better/stronger/faster and able to deal with these weaker signal levels, but
the signal has continued to degrade over the past two months until the point
that it too no longer can deal with the weakened signal, and drops out with
interference from the TV. I was getting -15 dBmV downstream, 50 dBmV
upstream, and an SNR of 29, which I gather from other postings on this site
(thanks Dave - your other posts have been very helpful) is very marginal.

I have temporarily moved the modem into the basement (not yet a permanent
solution, as the wireless is no longer attached to the printer upstairs in my
office, but is instead hanging in the basement with the modem). There was
one unecessary 3-way splitter down there (the 3.5 dB drop came upstairs to
the TV/modem, the two 7 dB drops were going to two cable hookups upstairs
that the previous owners used, but we don't - I had told Comcast not to hook
those up last they were out, it seems they didn't listen). I have removed
the 3-way split, and put in a two way split. So, right now, it's outside ->
digital phone box -> 2-way split, with one split going directly to the modem.
I.e., about as close to the source as I can get. With that, I now get -7
dBmV downstream, 37 dBmV upstream, and a SNR of 36, even with the TV on. Now,
that's much better, but given that I am pretty much as close to the source as
I can get, I had hoped for a little bit better. (I've certainly seen others
on this site reference slightly better numbers, especially on the downstream
side.)

Plus, I am in general worried about this possible recent trend of degrading
signal quality. It still seems worthwhile to have Comcast to come out on
Saturday morning to see if there is anything they can do to boost the signal
quality coming into the house, and maybe even do the TV/modem split outside
of the house, so I can get rid of one more internal splittler.

.

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