Ralph, I'd ask your cable provider what they recommend. Every system is different and they will/should have the best answer. They may even provide what you need at no cost to you.
Unless Comcast is pushing channels on non-standard frequencies, you should only need a cable box for scrambled channels. Also splitting the cable for the modem may have lowered the signal strength to the TV. This can be especially true if you are splitting it for several tv sets/devices!
I have on occasion seen compatibility issues between some models of tv set and cable systems. Canton, Oh's system with Samsung comes to mind. All the more reason to contact Comcast.
Who suggested the low pass filter? The bandwith of such a filter would depend on what it is you are trying to reject. Without more info I would not even want to guess!
I have found that hand tools are the best choice when I want to make mistakes at a slower rate of speed.
I don't suffer from insanity. I enjoy every minute of it.
Last edited by Dmeadows; 11-08-2013 at 11:35 AM.