could be the weather.
wind and other weather causes bad reception when using an antenna and cable/satalite can also be affected by the weather.
ya, cable!
We were having reception problems with our cable and the company said that at certain angles and weather conditions they have problems transmitting the signals from the satellites.
Also maybe you need a ground?

Inteference problems are a pain to diagnose, but the good news is that in just about every case the cause can be located. Since your inteference problem is recent you should look for changes that may have occured in and around your home recently.

Also, since hte interference affects sets connected to both inside and outside antennas it is safe to rule out cable and ground issues, atleast as far as the antennas go.

Since the inteference also affects all channels, it is rather unlikely that weather conditions alone are to blame. Weather conditions typically will either 1.) attenuate distance signals making them noisier or blanking them out completely, or 2.) allowing distant signals on the same channel to travel farther thus causing inteference to nearby stations. While #2 could still be a likely cause, I'm thinkin something electrical is to blame.

The questions I normally as are:

1. Have you purchases/installed/connected any electronics, appliances, computers, ANYTHING electric around the time the inteference began?

2. To the best of your knowledge has any of your immediate neighbors done the same in regards to new electrical equipment.

3. Look for cause-effect relationships. Does the inteference start when someone dries their hair, uses an electric shaver, does laundry, etc.

4. Any new construction nearby? Power tools, especially arc welders can cause electrical noise from longer distances, sometimes ranging from hundreds to thousands of feet.

5. Probably not applicable down there, but electric heat and water heaters if they develop a problem can cause inteference too.

There are other tips, but I think you get the idea. If you still get stuck, don't hesitate to call one of your local tv stations and ask for some guidance. Make sure you ask for someone in the engineering department, they are used to dealing with these issues on a regular basis.

Best of luck!

- Steve

Thank you for the help. The only thing that was done recently was repair of the connection from rooftop antenna leading to the TV in the den. The inteference was only on the channels from that source for a few days and then it bled over to the analog (Ch4) CBand channel. A few days later it bled over (only slightly) to the digital TV channel. It only comes some times on some days and never for more than a few hours at a time. I haven't seen it for about a week, however their has been more sparkles on the screen since that time with all channels. Help!

Sounds to me like a combination of several factors (but I'm just speculating from the small amount of info provided). I think that your repair work introduced a coaxial cable with a bad connector/connection on the shield. That in combination with a poor ground and a nearby TV/FM (etc) transmitter nearby could cause the widespread problems you're seeing.

To fix it, I would double check all the connections that were touched by the rooftop antenna repair (or call back the repair folks). And I'd verify that the rooftop antenna (coax cable) is connected to a good earth ground like a cold water pipe.