Cisco DPC 3848 question

aquos · Post by **aquos** » Tue Jun 09, 2015 7:36 pm

Can anyone tell me if these power levels are ok or not?
My modem keeps rebooting once or twice a day. I'm on a 100/10
Modem: CISCO DPC 3848

Downstream:

Power Level: SNR:

Channel 1: 15.300 dBmV 38.60dB
Channel 2: 15.200 dBmV 38.60dB
Channel 3: 14.900 dBmV 38.98dB
Channel 4: 15.100 dBmV 38.60dB
Channel 5: 15.200 dBmV 38.98dB
Channel 6: 15.100 dBmV 38.98dB
Channel 7: 15.400 dBmV 38.98dB
Channel 8: 15.300 dBmV 38.60dB
Channel 9: 15.200 dBmV 38.60dB
Channel 10: 15.300 dBmV 38.60dB
Channel 11: 15.500 dBmV 38.98dB
Channel 12: 15.700 dBmV 38.98dB
Channel 13: 15.700 dBmV 38.60dB
Channel 14: 15.600 dBmV 38.60dB
Channel 15: 16.100 dBmV 38.98dB
Channel 16: 16.300 dBmV 38.60dB
Channel 17: 16.400 dBmV 38.60dB
Channel 18: 16.200 dBmV 38.98dB
Channel 19: 16.100 dBmV 38.60dB
Channel 20: 15.900 dBmV 38.60dB

Upstream:

Power Level:

Channel1 : 45.750 dBmV
Channel2 : 47.750 dBmV
Channel3 : 46.250 dBmV

Post by **Philip** » Tue Jun 09, 2015 9:08 pm

Welcome to the SG Forums aquos.

Downstream SNR is good.
Upstream power is good.

Downstream Power Level is too high/hot... Does it always stay around/over 15 ?
It's best if you can keep it between -8 and +8 dBmV, theoretically it can be between -15 and +15, but the closer it is to zero, the better. Yours is over +15. I'd just reduce it with a splitter, put a 2-way or a 3-way splitter on the coax before the cable modem. Each 2-way split reduces it by 3.5dB on each output leg, a 4-way splitter by 7db on each leg. Alternatively, tell your Cable company your downstream power is too high and your modem is rebooting, so that they can send in a technician to check the line.

There is a bit more info on what the numbers should be here: http://www.speedguide.net/faq/what-cabl ... ed-good-78

aquos · Post by **aquos** » Wed Jun 10, 2015 5:44 pm

I've reduced my dbmv with "two" 2 way splitters and the results are: wall>splitter>short RG6>splitter>RG6 to modem. Is that good now or should I throw another splitter 3 in total to go lower dbmv?

Downstream:

Channel

Power Level:

Signal to Noise Ratio:

Channel 1: 8.400 dBmV 38.60dB
Channel 2: 8.200 dBmV 38.98dB
Channel 3: 8.000 dBmV 38.60dB
Channel 4: 8.200 dBmV 38.60dB
Channel 5: 8.300 dBmV 38.60dB
Channel 6: 8.200 dBmV 38.98dB
Channel 7: 8.200 dBmV 38.98dB
Channel 8: 8.500 dBmV 38.60dB
Channel 9: 8.400 dBmV 38.98dB
Channel 10: 8.400 dBmV 38.98dB
Channel 11: 8.400 dBmV 38.60dB
Channel 12: 8.500 dBmV 38.98dB
Channel 13: 8.400 dBmV 38.98dB
Channel 14: 8.300 dBmV 38.60dB
Channel 15: 8.900 dBmV 38.60dB
Channel 16: 9.200 dBmV 38.98dB
Channel 17: 9.200 dBmV 38.60dB
Channel 18: 9.000 dBmV 38.98dB
Channel 19: 8.900 dBmV 38.60dB
Channel 20: 8.800 dBmV 38.60dB

Upstream:

Channel

Power Level:

Channel1 : 46.250 dBmV
Channel2 : 46.250 dBmV
Channel3 : 46.250 dBmV

Post by **Philip** » Wed Jun 10, 2015 5:49 pm

No, you shouldn't add another splitter, it seems fine as is. I wonder why your downstream power was so high, they shouldn't have left it that way when installing.
Does your modem seem more stable ?

aquos · Post by **aquos** » Wed Jun 10, 2015 7:28 pm

Thanks for your help. So far my modem works fine no reboots (hopefully

. The reason my power was high cause I upgraded from my existing modem to this 24/8 one. I installed it myself.

Post by **Philip** » Wed Jun 10, 2015 10:08 pm

Still, just swapping modems (everything else equal) should not change the downstream power, that is the strength of the incoming signal to the modem, it was just too much. Some modems are more sensitive than others, but +16 is outside the acceptable/recommended range.