Cable Modem - To Filter or Not to Filter

smitbret

Diamond Member
Jul 27, 2006
3,382
17
81
Motorola Surfboard DocSis 3.0

I moved my setup around a little bit and when I moved the modem to a new location in my house, I noticed the installing tech put a little screw on filter on the back of the modem. I wondered if I needed it at the new location since the coax is about 50 feet longer from the drop so I did a signal check on the modem with and without the filter

Without:
Downstream SNR: 42db
Downstream Power: 2 5 2 2 (the five dips as low as 3 and back up if I refresh)
Upstream SNR: 29db
Upstream Level: Modem doesn't provide this

With Filter:
Downstream SNR: 42db
Downstream Power: -2 -2 -2 -2
Upstream SNR: 37db

SpeedGuide says the downstream is fine but the 29db on the Upstream SNR is right there at the bottom of the recommended range. Putting the filter on really makes a big difference (up to 37db) but the Downstream power drops from 2 to -2.

Which set of readings is best?
 

Ben90

Platinum Member
Jun 14, 2009
2,866
3
0
Your SNR is better with the filter and the power pretty much doesn't change. You ideally want to have your power at 0, but anything +-10 is fine. Keep the filter on.
In any case it won't matter too much unless you have crazy internet, your SNR and power destroys mine and I speedtest 130Mb/11Mb all day everyday.
 

smitbret

Diamond Member
Jul 27, 2006
3,382
17
81
Your SNR is better with the filter and the power pretty much doesn't change. You ideally want to have your power at 0, but anything +-10 is fine. Keep the filter on.
In any case it won't matter too much unless you have crazy internet, your SNR and power destroys mine and I speedtest 130Mb/11Mb all day everyday.

Cool, thanks.