My townhouse is wired for Internet access and an Ethernet LAN on all floors. The LAN uses unshielded Category 5 cable. In the loft this cable is within a few feet of the antennas. Internet access was recently (Oct 2003) changed to Comcast cable modem from a dedicated DSL line. Data rate is approximately 3 Mbps and reliability has been excellent. Below is a simplified diagram of my network. As Nov 2004, the firewall router shown on the diagram has operated more 230 days without rebooting! Note that a multiple hub junction is located very close to the antenna suite. Only when I am downloading a large file is any interference noticed on my HF receiver.
Although cable TV is wired to the community and my immediate neighbors, I have used Dish direct broadcast TV. Satellite TV receivers are connected on the 2 floors below my antenna suite. I also have the normal complement of telephones, both wired and wireless throughout the house. I have seen no interference to these receivers nor to the telephones.
Along with my conversion to Comcast cable modem for internet service, I have decided to use cable TV rather than satellite. With digital cable the channel lines are equivalent and costs are very similar.
I am currently experiencing one source of interference that appears unresolvable. I have a large Toshiba color television in my living room. The color burst oscillator is generating interference on the 80 meter band at common PSK31 frequencies (approximately 3.580 Mhz).
My normal ham operations are at QRP (< 5 watts) power levels. I have briefly operated at moderate levels of 20-25 watts. Without any interference. I do not ever expect to run full power (100 watts) in this location. Even if my electronics can withstand the power (treated or untreated), the close proximity to my neighbors is inviting complaints. And besides, QRP is fun!!! Check this page in the future for additional results.
In the mean time, I recommend always operating with minimum power. This axiom of hamming is true particularly with attic antennas and close proximity to neighbors.