TV interference

[DTraveller]

Hi, I have a Sky+ box in the lounge (which gets a spot-on signal) and in addition to that i have four additional TVs (some new flat screens) in other rooms that were installed by a professional. These additional sets recieve alot of interference (although they didn't when the installer was here - typical!). Sometimes it is when using broadband, dialup internet, the electric oven or even the washing machine but some times it is for no apparent reason. We have quite a bit of space around the house and dont think the interference is coming from a nearby house. Also get interference on digital and terrestrial tv.
When this interference occurs on the extra TVs, it does not seem to have any effect on the 50" plasma in the lounge!
Any ideas or suggestions please?

[ericmark]

I also had problems my sky was wired into all bedrooms and worked great for years then stopped working. After a long time I found the sky box RF output frequency is now used by freeview since the former is analogue and the latter digital which with sky I don't use I had not realized what had gone wrong. The sky box is old and not re-tuneable latter ones have software tuning. It is on same frequency as channel 5 and it seems many people in the area are having problems with channel 5 on freeview so the EMC problem is going both ways. channel 5 can often be cured by moving the aerial a few feet to left or right.
In general the weaker the signal the more likely to get interference so aerial moved or damaged. Amplifiers then to make it worse and there are some band pass filters that can improve things.
Water in coaxial cable can be problem. If you have a distribution unit in loft the signal normally goes to main TV and Sky box then back up to loft which is why no faults on 50" TV although it is one box it is really two with an combiner and splitter to send signals up and down to main TV and amp and distribution unit to do bed rooms. Often they take power from lights for latter section if mistake was made maybe it is switching on and off with some lights? And the very simple of a plug becoming loose. This can happen where F type plugs and sockets are used on non sky cable which is slightly thinner.
I hope the pointers will help.