I have a Motorola SB6141 cable modem about 5 feet away from my Yaesu FT-450AT. Unfortunately, it seems to be contributing to about 2 S-units of noise on at least some of 40 meters when powered. I replaced the wall wart with a direct connection to the shack's 12V supply with no change, as well as placed snap-on ferrites on almost all of the wires coming out of it except for the coax feed. I'd put a choke on the coax feed too, but the modem's status page said that it was using 28MHz for uplink, so it's probably not a good idea.
Is there anything else I can do besides going without Internet while on the air? (My setup is already pretty marginal as is due to being HOA restricted in a condo, so I'd like to try to improve my S/N ratio as much as possible.) Also, would something like the ANC-4 help?
I had a friend that had a similar problem and he shielded it using a metal case and grounding it. The problem is that I cannot recall if it solved it. It was a while ago. I suppose it would be cheap enough to give it a shot.